Introduce MessageReflector to enable alternative protobuf runtimes

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 assertj = "3.27.7"
 buf = "1.70.0"
-cel = "0.13.0"
+cel = "0.13.1"
 error-prone = "2.49.0"
 junit = "5.14.4"
 maven-publish = "0.36.0"

src/main/java/build/buf/protovalidate/AnyEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldPath;
 import build.buf.validate.FieldRules;
 import com.google.protobuf.Descriptors;
-import com.google.protobuf.Message;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -78,12 +77,12 @@ final class AnyEvaluator implements Evaluator {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message anyValue = val.messageValue();
+MessageReflector anyValue = val.messageValue();
  if (anyValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
  List<RuleViolation.Builder> violationList = new ArrayList<>();
- String typeURL = (String) anyValue.getField(typeURLDescriptor);
+ String typeURL = anyValue.getField(typeURLDescriptor).jvmValue(String.class);
  if (!in.isEmpty() && !in.contains(typeURL)) {
  RuleViolation.Builder violation =
  RuleViolation.newBuilder()

src/main/java/build/buf/protovalidate/CelPrograms.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- CelVariableResolver bindings = Variable.newThisVariable(val.value(Object.class));
+ CelVariableResolver bindings = Variable.newThisVariable(val.celValue());
  List<RuleViolation.Builder> violations = new ArrayList<>();
  for (CompiledProgram program : programs) {
  RuleViolation.Builder violation = program.eval(val, bindings);

src/main/java/build/buf/protovalidate/EnumEvaluator.java

@@ -77,7 +77,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Object enumValue = val.value(Object.class);
+Long enumValue = val.jvmValue(Long.class);
  if (enumValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/FieldEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldRules;
 import build.buf.validate.Ignore;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -95,7 +94,7 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreAlways()) {
  return RuleViolation.NO_VIOLATIONS;
  }
-Message message = val.messageValue();
+MessageReflector message = val.messageValue();
  if (message == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
@@ -113,17 +112,19 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreEmpty() && !hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
- return valueEvaluator.evaluate(
- new ObjectValue(descriptor, message.getField(descriptor)), failFast);
+ return valueEvaluator.evaluate(message.getField(descriptor), failFast);
  }
 
  /**
  * Returns whether the given field is set on the message. Handles repeated and map fields, which
- * are not supported by {@link Message#hasField}.
+ * require inspecting the list/map contents rather than a presence bit.
  */
- static boolean isFieldSet(Message message, FieldDescriptor field) {
+ static boolean isFieldSet(MessageReflector message, FieldDescriptor field) {
  if (field.isRepeated()) {
- return message.getRepeatedFieldCount(field) != 0;
+ if (field.isMapField()) {
+ return !message.getField(field).mapValue().isEmpty();
+ }
+ return !message.getField(field).repeatedValue().isEmpty();
  }
  return message.hasField(field);
  }

src/main/java/build/buf/protovalidate/ListElementValue.java

@@ -45,15 +45,20 @@ final class ListElementValue implements Value {
  }
 
  @Override
- public @Nullable Message messageValue() {
+ public @Nullable MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.scalarToCel(fieldDescriptor.getType(), value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
  Descriptors.FieldDescriptor.Type type = fieldDescriptor.getType();
  if (type == Descriptors.FieldDescriptor.Type.MESSAGE) {
  return clazz.cast(value);

src/main/java/build/buf/protovalidate/MapEvaluator.java

@@ -155,19 +155,19 @@ private List<RuleViolation.Builder> evalPairs(Value key, Value value, boolean fa
  case TYPE_SINT64:
  case TYPE_SFIXED32:
  case TYPE_SFIXED64:
- fieldPathElementBuilder.setIntKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setIntKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_UINT32:
  case TYPE_UINT64:
  case TYPE_FIXED32:
  case TYPE_FIXED64:
- fieldPathElementBuilder.setUintKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setUintKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_BOOL:
- fieldPathElementBuilder.setBoolKey(key.value(Boolean.class));
+ fieldPathElementBuilder.setBoolKey(key.jvmValue(Boolean.class));
  break;
  case TYPE_STRING:
- fieldPathElementBuilder.setStringKey(key.value(String.class));
+ fieldPathElementBuilder.setStringKey(key.jvmValue(String.class));
  break;
  default:
  throw new ExecutionException("Unexpected map key type");

src/main/java/build/buf/protovalidate/MessageOneofEvaluator.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message msg = val.messageValue();
+MessageReflector msg = val.messageValue();
  if (msg == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/MessageReflector.java

@@ -0,0 +1,59 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+/**
+ * {@link MessageReflector} is a wrapper around a protobuf message that provides reflective access
+ * to the underlying message.
+ *
+ * <p>{@link MessageReflector} is a runtime-independent interface. Any protobuf runtime that
+ * implements this interface can wrap its messages so that protovalidate-java can validate them.
+ */
+public interface MessageReflector {
+ /**
+ * The {@link Descriptor} of the wrapped message's type.
+ *
+ * @return The descriptor.
+ */
+ Descriptor getDescriptorForType();
+
+ /**
+ * Whether the wrapped message has the field described by the provided field descriptor.
+ *
+ * @param field The field descriptor to check for.
+ * @return Whether the field is present.
+ */
+ boolean hasField(FieldDescriptor field);
+
+ /**
+ * Get the value described by the provided field descriptor.
+ *
+ * @param field The field descriptor for which to retrieve a value.
+ * @return The value corresponding to the field descriptor.
+ */
+ Value getField(FieldDescriptor field);
+
+ /**
+ * Returns the representation of this message to hand to CEL for {@code this}-variable rule
+ * evaluation. Implementations return whichever form CEL can navigate for their runtime, such as
+ * a {@link com.google.protobuf.Message} or a {@code dev.cel.common.values.CelValue}.
+ *
+ * @return The CEL-navigable representation of this message.
+ */
+ Object celValue();
+}

src/main/java/build/buf/protovalidate/MessageReflectorValue.java

@@ -0,0 +1,66 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import org.jspecify.annotations.Nullable;
+
+/** Top-level {@link Value} backed by a user-supplied {@link MessageReflector}. */
+final class MessageReflectorValue implements Value {
+
+ private final MessageReflector reflector;
+
+ MessageReflectorValue(MessageReflector reflector) {
+ this.reflector = reflector;
+ }
+
+ @Override
+ public Descriptors.@Nullable FieldDescriptor fieldDescriptor() {
+ return null;
+ }
+
+ @Override
+ public MessageReflector messageValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object rawValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object celValue() {
+ return reflector.celValue();
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public List<Value> repeatedValue() {
+ return Collections.emptyList();
+ }
+
+ @Override
+ public Map<Value, Value> mapValue() {
+ return Collections.emptyMap();
+ }
+}

src/main/java/build/buf/protovalidate/MessageValue.java

@@ -24,16 +24,15 @@
 /** The {@link Value} type that contains a {@link com.google.protobuf.Message}. */
 final class MessageValue implements Value {
 
- /** Object type since the object type is inferred from the field descriptor. */
- private final Object value;
+ private final ProtobufMessageReflector value;
 
  /**
  * Constructs a {@link MessageValue} with the provided message value.
  *
  * @param value The message value.
  */
  MessageValue(Message value) {
- this.value = value;
+ this.value = new ProtobufMessageReflector(value);
  }
 
  @Override
@@ -42,13 +41,18 @@ final class MessageValue implements Value {
  }
 
  @Override
- public Message messageValue() {
- return (Message) value;
+ public MessageReflector messageValue() {
+ return value;
+ }
+
+ @Override
+ public Object celValue() {
+ return value.getMessage();
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
-return clazz.cast(value);
+ public <T> T jvmValue(Class<T> clazz) {
+throw new UnsupportedOperationException();
  }
 
  @Override

src/main/java/build/buf/protovalidate/ObjectValue.java

@@ -53,15 +53,23 @@ public Descriptors.FieldDescriptor fieldDescriptor() {
 
  @Nullable
  @Override
- public Message messageValue() {
+ public MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.toCel(fieldDescriptor, value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ if (value instanceof Descriptors.EnumValueDescriptor) {
+ return clazz.cast((long) ((Descriptors.EnumValueDescriptor) value).getNumber());
+ }
  return clazz.cast(ProtoAdapter.toCel(fieldDescriptor, value));
  }
 

src/main/java/build/buf/protovalidate/OneofEvaluator.java

@@ -17,7 +17,6 @@
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.FieldPathElement;
 import com.google.protobuf.Descriptors.OneofDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -48,8 +47,12 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- Message message = val.messageValue();
- if (message == null || !required || (message.getOneofFieldDescriptor(descriptor) != null)) {
+ MessageReflector message = val.messageValue();
+ if (message == null) {
+ return RuleViolation.NO_VIOLATIONS;
+ }
+ boolean hasField = descriptor.getFields().stream().anyMatch(message::hasField);
+ if (!required || hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
  return Collections.singletonList(

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 assertj = "3.27.7"
 buf = "1.70.0"
-cel = "0.13.0"
+cel = "0.13.1"
 error-prone = "2.49.0"
 junit = "5.14.4"
 maven-publish = "0.36.0"

src/main/java/build/buf/protovalidate/AnyEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldPath;
 import build.buf.validate.FieldRules;
 import com.google.protobuf.Descriptors;
-import com.google.protobuf.Message;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -78,12 +77,12 @@ final class AnyEvaluator implements Evaluator {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message anyValue = val.messageValue();
+MessageReflector anyValue = val.messageValue();
  if (anyValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
  List<RuleViolation.Builder> violationList = new ArrayList<>();
- String typeURL = (String) anyValue.getField(typeURLDescriptor);
+ String typeURL = anyValue.getField(typeURLDescriptor).jvmValue(String.class);
  if (!in.isEmpty() && !in.contains(typeURL)) {
  RuleViolation.Builder violation =
  RuleViolation.newBuilder()

src/main/java/build/buf/protovalidate/CelPrograms.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- CelVariableResolver bindings = Variable.newThisVariable(val.value(Object.class));
+ CelVariableResolver bindings = Variable.newThisVariable(val.celValue());
  List<RuleViolation.Builder> violations = new ArrayList<>();
  for (CompiledProgram program : programs) {
  RuleViolation.Builder violation = program.eval(val, bindings);

src/main/java/build/buf/protovalidate/EnumEvaluator.java

@@ -77,7 +77,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Object enumValue = val.value(Object.class);
+Long enumValue = val.jvmValue(Long.class);
  if (enumValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/FieldEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldRules;
 import build.buf.validate.Ignore;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -95,7 +94,7 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreAlways()) {
  return RuleViolation.NO_VIOLATIONS;
  }
-Message message = val.messageValue();
+MessageReflector message = val.messageValue();
  if (message == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
@@ -113,17 +112,19 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreEmpty() && !hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
- return valueEvaluator.evaluate(
- new ObjectValue(descriptor, message.getField(descriptor)), failFast);
+ return valueEvaluator.evaluate(message.getField(descriptor), failFast);
  }
 
  /**
  * Returns whether the given field is set on the message. Handles repeated and map fields, which
- * are not supported by {@link Message#hasField}.
+ * require inspecting the list/map contents rather than a presence bit.
  */
- static boolean isFieldSet(Message message, FieldDescriptor field) {
+ static boolean isFieldSet(MessageReflector message, FieldDescriptor field) {
  if (field.isRepeated()) {
- return message.getRepeatedFieldCount(field) != 0;
+ if (field.isMapField()) {
+ return !message.getField(field).mapValue().isEmpty();
+ }
+ return !message.getField(field).repeatedValue().isEmpty();
  }
  return message.hasField(field);
  }

src/main/java/build/buf/protovalidate/ListElementValue.java

@@ -45,15 +45,20 @@ final class ListElementValue implements Value {
  }
 
  @Override
- public @Nullable Message messageValue() {
+ public @Nullable MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.scalarToCel(fieldDescriptor.getType(), value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
  Descriptors.FieldDescriptor.Type type = fieldDescriptor.getType();
  if (type == Descriptors.FieldDescriptor.Type.MESSAGE) {
  return clazz.cast(value);

src/main/java/build/buf/protovalidate/MapEvaluator.java

@@ -155,19 +155,19 @@ private List<RuleViolation.Builder> evalPairs(Value key, Value value, boolean fa
  case TYPE_SINT64:
  case TYPE_SFIXED32:
  case TYPE_SFIXED64:
- fieldPathElementBuilder.setIntKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setIntKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_UINT32:
  case TYPE_UINT64:
  case TYPE_FIXED32:
  case TYPE_FIXED64:
- fieldPathElementBuilder.setUintKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setUintKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_BOOL:
- fieldPathElementBuilder.setBoolKey(key.value(Boolean.class));
+ fieldPathElementBuilder.setBoolKey(key.jvmValue(Boolean.class));
  break;
  case TYPE_STRING:
- fieldPathElementBuilder.setStringKey(key.value(String.class));
+ fieldPathElementBuilder.setStringKey(key.jvmValue(String.class));
  break;
  default:
  throw new ExecutionException("Unexpected map key type");

src/main/java/build/buf/protovalidate/MessageOneofEvaluator.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message msg = val.messageValue();
+MessageReflector msg = val.messageValue();
  if (msg == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/MessageReflector.java

@@ -0,0 +1,59 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+/**
+ * {@link MessageReflector} is a wrapper around a protobuf message that provides reflective access
+ * to the underlying message.
+ *
+ * <p>{@link MessageReflector} is a runtime-independent interface. Any protobuf runtime that
+ * implements this interface can wrap its messages so that protovalidate-java can validate them.
+ */
+public interface MessageReflector {
+ /**
+ * The {@link Descriptor} of the wrapped message's type.
+ *
+ * @return The descriptor.
+ */
+ Descriptor getDescriptorForType();
+
+ /**
+ * Whether the wrapped message has the field described by the provided field descriptor.
+ *
+ * @param field The field descriptor to check for.
+ * @return Whether the field is present.
+ */
+ boolean hasField(FieldDescriptor field);
+
+ /**
+ * Get the value described by the provided field descriptor.
+ *
+ * @param field The field descriptor for which to retrieve a value.
+ * @return The value corresponding to the field descriptor.
+ */
+ Value getField(FieldDescriptor field);
+
+ /**
+ * Returns the representation of this message to hand to CEL for {@code this}-variable rule
+ * evaluation. Implementations return whichever form CEL can navigate for their runtime, such as
+ * a {@link com.google.protobuf.Message} or a {@code dev.cel.common.values.CelValue}.
+ *
+ * @return The CEL-navigable representation of this message.
+ */
+ Object celValue();
+}

src/main/java/build/buf/protovalidate/MessageReflectorValue.java

@@ -0,0 +1,66 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import org.jspecify.annotations.Nullable;
+
+/** Top-level {@link Value} backed by a user-supplied {@link MessageReflector}. */
+final class MessageReflectorValue implements Value {
+
+ private final MessageReflector reflector;
+
+ MessageReflectorValue(MessageReflector reflector) {
+ this.reflector = reflector;
+ }
+
+ @Override
+ public Descriptors.@Nullable FieldDescriptor fieldDescriptor() {
+ return null;
+ }
+
+ @Override
+ public MessageReflector messageValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object rawValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object celValue() {
+ return reflector.celValue();
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public List<Value> repeatedValue() {
+ return Collections.emptyList();
+ }
+
+ @Override
+ public Map<Value, Value> mapValue() {
+ return Collections.emptyMap();
+ }
+}

src/main/java/build/buf/protovalidate/MessageValue.java

@@ -24,16 +24,15 @@
 /** The {@link Value} type that contains a {@link com.google.protobuf.Message}. */
 final class MessageValue implements Value {
 
- /** Object type since the object type is inferred from the field descriptor. */
- private final Object value;
+ private final ProtobufMessageReflector value;
 
  /**
  * Constructs a {@link MessageValue} with the provided message value.
  *
  * @param value The message value.
  */
  MessageValue(Message value) {
- this.value = value;
+ this.value = new ProtobufMessageReflector(value);
  }
 
  @Override
@@ -42,13 +41,18 @@ final class MessageValue implements Value {
  }
 
  @Override
- public Message messageValue() {
- return (Message) value;
+ public MessageReflector messageValue() {
+ return value;
+ }
+
+ @Override
+ public Object celValue() {
+ return value.getMessage();
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
-return clazz.cast(value);
+ public <T> T jvmValue(Class<T> clazz) {
+throw new UnsupportedOperationException();
  }
 
  @Override

src/main/java/build/buf/protovalidate/ObjectValue.java

@@ -53,15 +53,23 @@ public Descriptors.FieldDescriptor fieldDescriptor() {
 
  @Nullable
  @Override
- public Message messageValue() {
+ public MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.toCel(fieldDescriptor, value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ if (value instanceof Descriptors.EnumValueDescriptor) {
+ return clazz.cast((long) ((Descriptors.EnumValueDescriptor) value).getNumber());
+ }
  return clazz.cast(ProtoAdapter.toCel(fieldDescriptor, value));
  }
 

src/main/java/build/buf/protovalidate/OneofEvaluator.java

@@ -17,7 +17,6 @@
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.FieldPathElement;
 import com.google.protobuf.Descriptors.OneofDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -48,8 +47,12 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- Message message = val.messageValue();
- if (message == null || !required || (message.getOneofFieldDescriptor(descriptor) != null)) {
+ MessageReflector message = val.messageValue();
+ if (message == null) {
+ return RuleViolation.NO_VIOLATIONS;
+ }
+ boolean hasField = descriptor.getFields().stream().anyMatch(message::hasField);
+ if (!required || hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
  return Collections.singletonList(

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 assertj = "3.27.7"
 buf = "1.70.0"
-cel = "0.13.0"
+cel = "0.13.1"
 error-prone = "2.49.0"
 junit = "5.14.4"
 maven-publish = "0.36.0"

src/main/java/build/buf/protovalidate/AnyEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldPath;
 import build.buf.validate.FieldRules;
 import com.google.protobuf.Descriptors;
-import com.google.protobuf.Message;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -78,12 +77,12 @@ final class AnyEvaluator implements Evaluator {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message anyValue = val.messageValue();
+MessageReflector anyValue = val.messageValue();
  if (anyValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
  List<RuleViolation.Builder> violationList = new ArrayList<>();
- String typeURL = (String) anyValue.getField(typeURLDescriptor);
+ String typeURL = anyValue.getField(typeURLDescriptor).jvmValue(String.class);
  if (!in.isEmpty() && !in.contains(typeURL)) {
  RuleViolation.Builder violation =
  RuleViolation.newBuilder()

src/main/java/build/buf/protovalidate/CelPrograms.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- CelVariableResolver bindings = Variable.newThisVariable(val.value(Object.class));
+ CelVariableResolver bindings = Variable.newThisVariable(val.celValue());
  List<RuleViolation.Builder> violations = new ArrayList<>();
  for (CompiledProgram program : programs) {
  RuleViolation.Builder violation = program.eval(val, bindings);

src/main/java/build/buf/protovalidate/EnumEvaluator.java

@@ -77,7 +77,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Object enumValue = val.value(Object.class);
+Long enumValue = val.jvmValue(Long.class);
  if (enumValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/FieldEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldRules;
 import build.buf.validate.Ignore;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -95,7 +94,7 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreAlways()) {
  return RuleViolation.NO_VIOLATIONS;
  }
-Message message = val.messageValue();
+MessageReflector message = val.messageValue();
  if (message == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
@@ -113,17 +112,19 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreEmpty() && !hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
- return valueEvaluator.evaluate(
- new ObjectValue(descriptor, message.getField(descriptor)), failFast);
+ return valueEvaluator.evaluate(message.getField(descriptor), failFast);
  }
 
  /**
  * Returns whether the given field is set on the message. Handles repeated and map fields, which
- * are not supported by {@link Message#hasField}.
+ * require inspecting the list/map contents rather than a presence bit.
  */
- static boolean isFieldSet(Message message, FieldDescriptor field) {
+ static boolean isFieldSet(MessageReflector message, FieldDescriptor field) {
  if (field.isRepeated()) {
- return message.getRepeatedFieldCount(field) != 0;
+ if (field.isMapField()) {
+ return !message.getField(field).mapValue().isEmpty();
+ }
+ return !message.getField(field).repeatedValue().isEmpty();
  }
  return message.hasField(field);
  }

src/main/java/build/buf/protovalidate/ListElementValue.java

@@ -45,15 +45,20 @@ final class ListElementValue implements Value {
  }
 
  @Override
- public @Nullable Message messageValue() {
+ public @Nullable MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.scalarToCel(fieldDescriptor.getType(), value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
  Descriptors.FieldDescriptor.Type type = fieldDescriptor.getType();
  if (type == Descriptors.FieldDescriptor.Type.MESSAGE) {
  return clazz.cast(value);

src/main/java/build/buf/protovalidate/MapEvaluator.java

@@ -155,19 +155,19 @@ private List<RuleViolation.Builder> evalPairs(Value key, Value value, boolean fa
  case TYPE_SINT64:
  case TYPE_SFIXED32:
  case TYPE_SFIXED64:
- fieldPathElementBuilder.setIntKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setIntKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_UINT32:
  case TYPE_UINT64:
  case TYPE_FIXED32:
  case TYPE_FIXED64:
- fieldPathElementBuilder.setUintKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setUintKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_BOOL:
- fieldPathElementBuilder.setBoolKey(key.value(Boolean.class));
+ fieldPathElementBuilder.setBoolKey(key.jvmValue(Boolean.class));
  break;
  case TYPE_STRING:
- fieldPathElementBuilder.setStringKey(key.value(String.class));
+ fieldPathElementBuilder.setStringKey(key.jvmValue(String.class));
  break;
  default:
  throw new ExecutionException("Unexpected map key type");

src/main/java/build/buf/protovalidate/MessageOneofEvaluator.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message msg = val.messageValue();
+MessageReflector msg = val.messageValue();
  if (msg == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/MessageReflector.java

@@ -0,0 +1,59 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+/**
+ * {@link MessageReflector} is a wrapper around a protobuf message that provides reflective access
+ * to the underlying message.
+ *
+ * <p>{@link MessageReflector} is a runtime-independent interface. Any protobuf runtime that
+ * implements this interface can wrap its messages so that protovalidate-java can validate them.
+ */
+public interface MessageReflector {
+ /**
+ * The {@link Descriptor} of the wrapped message's type.
+ *
+ * @return The descriptor.
+ */
+ Descriptor getDescriptorForType();
+
+ /**
+ * Whether the wrapped message has the field described by the provided field descriptor.
+ *
+ * @param field The field descriptor to check for.
+ * @return Whether the field is present.
+ */
+ boolean hasField(FieldDescriptor field);
+
+ /**
+ * Get the value described by the provided field descriptor.
+ *
+ * @param field The field descriptor for which to retrieve a value.
+ * @return The value corresponding to the field descriptor.
+ */
+ Value getField(FieldDescriptor field);
+
+ /**
+ * Returns the representation of this message to hand to CEL for {@code this}-variable rule
+ * evaluation. Implementations return whichever form CEL can navigate for their runtime, such as
+ * a {@link com.google.protobuf.Message} or a {@code dev.cel.common.values.CelValue}.
+ *
+ * @return The CEL-navigable representation of this message.
+ */
+ Object celValue();
+}

src/main/java/build/buf/protovalidate/MessageReflectorValue.java

@@ -0,0 +1,66 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import org.jspecify.annotations.Nullable;
+
+/** Top-level {@link Value} backed by a user-supplied {@link MessageReflector}. */
+final class MessageReflectorValue implements Value {
+
+ private final MessageReflector reflector;
+
+ MessageReflectorValue(MessageReflector reflector) {
+ this.reflector = reflector;
+ }
+
+ @Override
+ public Descriptors.@Nullable FieldDescriptor fieldDescriptor() {
+ return null;
+ }
+
+ @Override
+ public MessageReflector messageValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object rawValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object celValue() {
+ return reflector.celValue();
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public List<Value> repeatedValue() {
+ return Collections.emptyList();
+ }
+
+ @Override
+ public Map<Value, Value> mapValue() {
+ return Collections.emptyMap();
+ }
+}

src/main/java/build/buf/protovalidate/MessageValue.java

@@ -24,16 +24,15 @@
 /** The {@link Value} type that contains a {@link com.google.protobuf.Message}. */
 final class MessageValue implements Value {
 
- /** Object type since the object type is inferred from the field descriptor. */
- private final Object value;
+ private final ProtobufMessageReflector value;
 
  /**
  * Constructs a {@link MessageValue} with the provided message value.
  *
  * @param value The message value.
  */
  MessageValue(Message value) {
- this.value = value;
+ this.value = new ProtobufMessageReflector(value);
  }
 
  @Override
@@ -42,13 +41,18 @@ final class MessageValue implements Value {
  }
 
  @Override
- public Message messageValue() {
- return (Message) value;
+ public MessageReflector messageValue() {
+ return value;
+ }
+
+ @Override
+ public Object celValue() {
+ return value.getMessage();
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
-return clazz.cast(value);
+ public <T> T jvmValue(Class<T> clazz) {
+throw new UnsupportedOperationException();
  }
 
  @Override

src/main/java/build/buf/protovalidate/ObjectValue.java

@@ -53,15 +53,23 @@ public Descriptors.FieldDescriptor fieldDescriptor() {
 
  @Nullable
  @Override
- public Message messageValue() {
+ public MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.toCel(fieldDescriptor, value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ if (value instanceof Descriptors.EnumValueDescriptor) {
+ return clazz.cast((long) ((Descriptors.EnumValueDescriptor) value).getNumber());
+ }
  return clazz.cast(ProtoAdapter.toCel(fieldDescriptor, value));
  }
 

src/main/java/build/buf/protovalidate/OneofEvaluator.java

@@ -17,7 +17,6 @@
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.FieldPathElement;
 import com.google.protobuf.Descriptors.OneofDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -48,8 +47,12 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- Message message = val.messageValue();
- if (message == null || !required || (message.getOneofFieldDescriptor(descriptor) != null)) {
+ MessageReflector message = val.messageValue();
+ if (message == null) {
+ return RuleViolation.NO_VIOLATIONS;
+ }
+ boolean hasField = descriptor.getFields().stream().anyMatch(message::hasField);
+ if (!required || hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
  return Collections.singletonList(

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 assertj = "3.27.7"
 buf = "1.70.0"
-cel = "0.13.0"
+cel = "0.13.1"
 error-prone = "2.49.0"
 junit = "5.14.4"
 maven-publish = "0.36.0"

src/main/java/build/buf/protovalidate/AnyEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldPath;
 import build.buf.validate.FieldRules;
 import com.google.protobuf.Descriptors;
-import com.google.protobuf.Message;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -78,12 +77,12 @@ final class AnyEvaluator implements Evaluator {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message anyValue = val.messageValue();
+MessageReflector anyValue = val.messageValue();
  if (anyValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
  List<RuleViolation.Builder> violationList = new ArrayList<>();
- String typeURL = (String) anyValue.getField(typeURLDescriptor);
+ String typeURL = anyValue.getField(typeURLDescriptor).jvmValue(String.class);
  if (!in.isEmpty() && !in.contains(typeURL)) {
  RuleViolation.Builder violation =
  RuleViolation.newBuilder()

src/main/java/build/buf/protovalidate/CelPrograms.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- CelVariableResolver bindings = Variable.newThisVariable(val.value(Object.class));
+ CelVariableResolver bindings = Variable.newThisVariable(val.celValue());
  List<RuleViolation.Builder> violations = new ArrayList<>();
  for (CompiledProgram program : programs) {
  RuleViolation.Builder violation = program.eval(val, bindings);

src/main/java/build/buf/protovalidate/EnumEvaluator.java

@@ -77,7 +77,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Object enumValue = val.value(Object.class);
+Long enumValue = val.jvmValue(Long.class);
  if (enumValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/FieldEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldRules;
 import build.buf.validate.Ignore;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -95,7 +94,7 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreAlways()) {
  return RuleViolation.NO_VIOLATIONS;
  }
-Message message = val.messageValue();
+MessageReflector message = val.messageValue();
  if (message == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
@@ -113,17 +112,19 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreEmpty() && !hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
- return valueEvaluator.evaluate(
- new ObjectValue(descriptor, message.getField(descriptor)), failFast);
+ return valueEvaluator.evaluate(message.getField(descriptor), failFast);
  }
 
  /**
  * Returns whether the given field is set on the message. Handles repeated and map fields, which
- * are not supported by {@link Message#hasField}.
+ * require inspecting the list/map contents rather than a presence bit.
  */
- static boolean isFieldSet(Message message, FieldDescriptor field) {
+ static boolean isFieldSet(MessageReflector message, FieldDescriptor field) {
  if (field.isRepeated()) {
- return message.getRepeatedFieldCount(field) != 0;
+ if (field.isMapField()) {
+ return !message.getField(field).mapValue().isEmpty();
+ }
+ return !message.getField(field).repeatedValue().isEmpty();
  }
  return message.hasField(field);
  }

src/main/java/build/buf/protovalidate/ListElementValue.java

@@ -45,15 +45,20 @@ final class ListElementValue implements Value {
  }
 
  @Override
- public @Nullable Message messageValue() {
+ public @Nullable MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.scalarToCel(fieldDescriptor.getType(), value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
  Descriptors.FieldDescriptor.Type type = fieldDescriptor.getType();
  if (type == Descriptors.FieldDescriptor.Type.MESSAGE) {
  return clazz.cast(value);

src/main/java/build/buf/protovalidate/MapEvaluator.java

@@ -155,19 +155,19 @@ private List<RuleViolation.Builder> evalPairs(Value key, Value value, boolean fa
  case TYPE_SINT64:
  case TYPE_SFIXED32:
  case TYPE_SFIXED64:
- fieldPathElementBuilder.setIntKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setIntKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_UINT32:
  case TYPE_UINT64:
  case TYPE_FIXED32:
  case TYPE_FIXED64:
- fieldPathElementBuilder.setUintKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setUintKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_BOOL:
- fieldPathElementBuilder.setBoolKey(key.value(Boolean.class));
+ fieldPathElementBuilder.setBoolKey(key.jvmValue(Boolean.class));
  break;
  case TYPE_STRING:
- fieldPathElementBuilder.setStringKey(key.value(String.class));
+ fieldPathElementBuilder.setStringKey(key.jvmValue(String.class));
  break;
  default:
  throw new ExecutionException("Unexpected map key type");

src/main/java/build/buf/protovalidate/MessageOneofEvaluator.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message msg = val.messageValue();
+MessageReflector msg = val.messageValue();
  if (msg == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/MessageReflector.java

@@ -0,0 +1,59 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+/**
+ * {@link MessageReflector} is a wrapper around a protobuf message that provides reflective access
+ * to the underlying message.
+ *
+ * <p>{@link MessageReflector} is a runtime-independent interface. Any protobuf runtime that
+ * implements this interface can wrap its messages so that protovalidate-java can validate them.
+ */
+public interface MessageReflector {
+ /**
+ * The {@link Descriptor} of the wrapped message's type.
+ *
+ * @return The descriptor.
+ */
+ Descriptor getDescriptorForType();
+
+ /**
+ * Whether the wrapped message has the field described by the provided field descriptor.
+ *
+ * @param field The field descriptor to check for.
+ * @return Whether the field is present.
+ */
+ boolean hasField(FieldDescriptor field);
+
+ /**
+ * Get the value described by the provided field descriptor.
+ *
+ * @param field The field descriptor for which to retrieve a value.
+ * @return The value corresponding to the field descriptor.
+ */
+ Value getField(FieldDescriptor field);
+
+ /**
+ * Returns the representation of this message to hand to CEL for {@code this}-variable rule
+ * evaluation. Implementations return whichever form CEL can navigate for their runtime, such as
+ * a {@link com.google.protobuf.Message} or a {@code dev.cel.common.values.CelValue}.
+ *
+ * @return The CEL-navigable representation of this message.
+ */
+ Object celValue();
+}

src/main/java/build/buf/protovalidate/MessageReflectorValue.java

@@ -0,0 +1,66 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import org.jspecify.annotations.Nullable;
+
+/** Top-level {@link Value} backed by a user-supplied {@link MessageReflector}. */
+final class MessageReflectorValue implements Value {
+
+ private final MessageReflector reflector;
+
+ MessageReflectorValue(MessageReflector reflector) {
+ this.reflector = reflector;
+ }
+
+ @Override
+ public Descriptors.@Nullable FieldDescriptor fieldDescriptor() {
+ return null;
+ }
+
+ @Override
+ public MessageReflector messageValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object rawValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object celValue() {
+ return reflector.celValue();
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public List<Value> repeatedValue() {
+ return Collections.emptyList();
+ }
+
+ @Override
+ public Map<Value, Value> mapValue() {
+ return Collections.emptyMap();
+ }
+}

src/main/java/build/buf/protovalidate/MessageValue.java

@@ -24,16 +24,15 @@
 /** The {@link Value} type that contains a {@link com.google.protobuf.Message}. */
 final class MessageValue implements Value {
 
- /** Object type since the object type is inferred from the field descriptor. */
- private final Object value;
+ private final ProtobufMessageReflector value;
 
  /**
  * Constructs a {@link MessageValue} with the provided message value.
  *
  * @param value The message value.
  */
  MessageValue(Message value) {
- this.value = value;
+ this.value = new ProtobufMessageReflector(value);
  }
 
  @Override
@@ -42,13 +41,18 @@ final class MessageValue implements Value {
  }
 
  @Override
- public Message messageValue() {
- return (Message) value;
+ public MessageReflector messageValue() {
+ return value;
+ }
+
+ @Override
+ public Object celValue() {
+ return value.getMessage();
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
-return clazz.cast(value);
+ public <T> T jvmValue(Class<T> clazz) {
+throw new UnsupportedOperationException();
  }
 
  @Override

src/main/java/build/buf/protovalidate/ObjectValue.java

@@ -53,15 +53,23 @@ public Descriptors.FieldDescriptor fieldDescriptor() {
 
  @Nullable
  @Override
- public Message messageValue() {
+ public MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.toCel(fieldDescriptor, value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ if (value instanceof Descriptors.EnumValueDescriptor) {
+ return clazz.cast((long) ((Descriptors.EnumValueDescriptor) value).getNumber());
+ }
  return clazz.cast(ProtoAdapter.toCel(fieldDescriptor, value));
  }
 

src/main/java/build/buf/protovalidate/OneofEvaluator.java

@@ -17,7 +17,6 @@
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.FieldPathElement;
 import com.google.protobuf.Descriptors.OneofDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -48,8 +47,12 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- Message message = val.messageValue();
- if (message == null || !required || (message.getOneofFieldDescriptor(descriptor) != null)) {
+ MessageReflector message = val.messageValue();
+ if (message == null) {
+ return RuleViolation.NO_VIOLATIONS;
+ }
+ boolean hasField = descriptor.getFields().stream().anyMatch(message::hasField);
+ if (!required || hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
  return Collections.singletonList(

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 assertj = "3.27.7"
 buf = "1.70.0"
-cel = "0.13.0"
+cel = "0.13.1"
 error-prone = "2.49.0"
 junit = "5.14.4"
 maven-publish = "0.36.0"

src/main/java/build/buf/protovalidate/AnyEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldPath;
 import build.buf.validate.FieldRules;
 import com.google.protobuf.Descriptors;
-import com.google.protobuf.Message;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -78,12 +77,12 @@ final class AnyEvaluator implements Evaluator {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message anyValue = val.messageValue();
+MessageReflector anyValue = val.messageValue();
  if (anyValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
  List<RuleViolation.Builder> violationList = new ArrayList<>();
- String typeURL = (String) anyValue.getField(typeURLDescriptor);
+ String typeURL = anyValue.getField(typeURLDescriptor).jvmValue(String.class);
  if (!in.isEmpty() && !in.contains(typeURL)) {
  RuleViolation.Builder violation =
  RuleViolation.newBuilder()

src/main/java/build/buf/protovalidate/CelPrograms.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- CelVariableResolver bindings = Variable.newThisVariable(val.value(Object.class));
+ CelVariableResolver bindings = Variable.newThisVariable(val.celValue());
  List<RuleViolation.Builder> violations = new ArrayList<>();
  for (CompiledProgram program : programs) {
  RuleViolation.Builder violation = program.eval(val, bindings);

src/main/java/build/buf/protovalidate/EnumEvaluator.java

@@ -77,7 +77,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Object enumValue = val.value(Object.class);
+Long enumValue = val.jvmValue(Long.class);
  if (enumValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/FieldEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldRules;
 import build.buf.validate.Ignore;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -95,7 +94,7 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreAlways()) {
  return RuleViolation.NO_VIOLATIONS;
  }
-Message message = val.messageValue();
+MessageReflector message = val.messageValue();
  if (message == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
@@ -113,17 +112,19 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreEmpty() && !hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
- return valueEvaluator.evaluate(
- new ObjectValue(descriptor, message.getField(descriptor)), failFast);
+ return valueEvaluator.evaluate(message.getField(descriptor), failFast);
  }
 
  /**
  * Returns whether the given field is set on the message. Handles repeated and map fields, which
- * are not supported by {@link Message#hasField}.
+ * require inspecting the list/map contents rather than a presence bit.
  */
- static boolean isFieldSet(Message message, FieldDescriptor field) {
+ static boolean isFieldSet(MessageReflector message, FieldDescriptor field) {
  if (field.isRepeated()) {
- return message.getRepeatedFieldCount(field) != 0;
+ if (field.isMapField()) {
+ return !message.getField(field).mapValue().isEmpty();
+ }
+ return !message.getField(field).repeatedValue().isEmpty();
  }
  return message.hasField(field);
  }

src/main/java/build/buf/protovalidate/ListElementValue.java

@@ -45,15 +45,20 @@ final class ListElementValue implements Value {
  }
 
  @Override
- public @Nullable Message messageValue() {
+ public @Nullable MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.scalarToCel(fieldDescriptor.getType(), value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
  Descriptors.FieldDescriptor.Type type = fieldDescriptor.getType();
  if (type == Descriptors.FieldDescriptor.Type.MESSAGE) {
  return clazz.cast(value);

src/main/java/build/buf/protovalidate/MapEvaluator.java

@@ -155,19 +155,19 @@ private List<RuleViolation.Builder> evalPairs(Value key, Value value, boolean fa
  case TYPE_SINT64:
  case TYPE_SFIXED32:
  case TYPE_SFIXED64:
- fieldPathElementBuilder.setIntKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setIntKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_UINT32:
  case TYPE_UINT64:
  case TYPE_FIXED32:
  case TYPE_FIXED64:
- fieldPathElementBuilder.setUintKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setUintKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_BOOL:
- fieldPathElementBuilder.setBoolKey(key.value(Boolean.class));
+ fieldPathElementBuilder.setBoolKey(key.jvmValue(Boolean.class));
  break;
  case TYPE_STRING:
- fieldPathElementBuilder.setStringKey(key.value(String.class));
+ fieldPathElementBuilder.setStringKey(key.jvmValue(String.class));
  break;
  default:
  throw new ExecutionException("Unexpected map key type");

src/main/java/build/buf/protovalidate/MessageOneofEvaluator.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message msg = val.messageValue();
+MessageReflector msg = val.messageValue();
  if (msg == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/MessageReflector.java

@@ -0,0 +1,59 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+/**
+ * {@link MessageReflector} is a wrapper around a protobuf message that provides reflective access
+ * to the underlying message.
+ *
+ * <p>{@link MessageReflector} is a runtime-independent interface. Any protobuf runtime that
+ * implements this interface can wrap its messages so that protovalidate-java can validate them.
+ */
+public interface MessageReflector {
+ /**
+ * The {@link Descriptor} of the wrapped message's type.
+ *
+ * @return The descriptor.
+ */
+ Descriptor getDescriptorForType();
+
+ /**
+ * Whether the wrapped message has the field described by the provided field descriptor.
+ *
+ * @param field The field descriptor to check for.
+ * @return Whether the field is present.
+ */
+ boolean hasField(FieldDescriptor field);
+
+ /**
+ * Get the value described by the provided field descriptor.
+ *
+ * @param field The field descriptor for which to retrieve a value.
+ * @return The value corresponding to the field descriptor.
+ */
+ Value getField(FieldDescriptor field);
+
+ /**
+ * Returns the representation of this message to hand to CEL for {@code this}-variable rule
+ * evaluation. Implementations return whichever form CEL can navigate for their runtime, such as
+ * a {@link com.google.protobuf.Message} or a {@code dev.cel.common.values.CelValue}.
+ *
+ * @return The CEL-navigable representation of this message.
+ */
+ Object celValue();
+}

src/main/java/build/buf/protovalidate/MessageReflectorValue.java

@@ -0,0 +1,66 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import org.jspecify.annotations.Nullable;
+
+/** Top-level {@link Value} backed by a user-supplied {@link MessageReflector}. */
+final class MessageReflectorValue implements Value {
+
+ private final MessageReflector reflector;
+
+ MessageReflectorValue(MessageReflector reflector) {
+ this.reflector = reflector;
+ }
+
+ @Override
+ public Descriptors.@Nullable FieldDescriptor fieldDescriptor() {
+ return null;
+ }
+
+ @Override
+ public MessageReflector messageValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object rawValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object celValue() {
+ return reflector.celValue();
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public List<Value> repeatedValue() {
+ return Collections.emptyList();
+ }
+
+ @Override
+ public Map<Value, Value> mapValue() {
+ return Collections.emptyMap();
+ }
+}

src/main/java/build/buf/protovalidate/MessageValue.java

@@ -24,16 +24,15 @@
 /** The {@link Value} type that contains a {@link com.google.protobuf.Message}. */
 final class MessageValue implements Value {
 
- /** Object type since the object type is inferred from the field descriptor. */
- private final Object value;
+ private final ProtobufMessageReflector value;
 
  /**
  * Constructs a {@link MessageValue} with the provided message value.
  *
  * @param value The message value.
  */
  MessageValue(Message value) {
- this.value = value;
+ this.value = new ProtobufMessageReflector(value);
  }
 
  @Override
@@ -42,13 +41,18 @@ final class MessageValue implements Value {
  }
 
  @Override
- public Message messageValue() {
- return (Message) value;
+ public MessageReflector messageValue() {
+ return value;
+ }
+
+ @Override
+ public Object celValue() {
+ return value.getMessage();
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
-return clazz.cast(value);
+ public <T> T jvmValue(Class<T> clazz) {
+throw new UnsupportedOperationException();
  }
 
  @Override

src/main/java/build/buf/protovalidate/ObjectValue.java

@@ -53,15 +53,23 @@ public Descriptors.FieldDescriptor fieldDescriptor() {
 
  @Nullable
  @Override
- public Message messageValue() {
+ public MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.toCel(fieldDescriptor, value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ if (value instanceof Descriptors.EnumValueDescriptor) {
+ return clazz.cast((long) ((Descriptors.EnumValueDescriptor) value).getNumber());
+ }
  return clazz.cast(ProtoAdapter.toCel(fieldDescriptor, value));
  }
 

src/main/java/build/buf/protovalidate/OneofEvaluator.java

@@ -17,7 +17,6 @@
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.FieldPathElement;
 import com.google.protobuf.Descriptors.OneofDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -48,8 +47,12 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- Message message = val.messageValue();
- if (message == null || !required || (message.getOneofFieldDescriptor(descriptor) != null)) {
+ MessageReflector message = val.messageValue();
+ if (message == null) {
+ return RuleViolation.NO_VIOLATIONS;
+ }
+ boolean hasField = descriptor.getFields().stream().anyMatch(message::hasField);
+ if (!required || hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
  return Collections.singletonList(

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 assertj = "3.27.7"
 buf = "1.70.0"
-cel = "0.13.0"
+cel = "0.13.1"
 error-prone = "2.49.0"
 junit = "5.14.4"
 maven-publish = "0.36.0"

src/main/java/build/buf/protovalidate/AnyEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldPath;
 import build.buf.validate.FieldRules;
 import com.google.protobuf.Descriptors;
-import com.google.protobuf.Message;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -78,12 +77,12 @@ final class AnyEvaluator implements Evaluator {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message anyValue = val.messageValue();
+MessageReflector anyValue = val.messageValue();
  if (anyValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
  List<RuleViolation.Builder> violationList = new ArrayList<>();
- String typeURL = (String) anyValue.getField(typeURLDescriptor);
+ String typeURL = anyValue.getField(typeURLDescriptor).jvmValue(String.class);
  if (!in.isEmpty() && !in.contains(typeURL)) {
  RuleViolation.Builder violation =
  RuleViolation.newBuilder()

src/main/java/build/buf/protovalidate/CelPrograms.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- CelVariableResolver bindings = Variable.newThisVariable(val.value(Object.class));
+ CelVariableResolver bindings = Variable.newThisVariable(val.celValue());
  List<RuleViolation.Builder> violations = new ArrayList<>();
  for (CompiledProgram program : programs) {
  RuleViolation.Builder violation = program.eval(val, bindings);

src/main/java/build/buf/protovalidate/EnumEvaluator.java

@@ -77,7 +77,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Object enumValue = val.value(Object.class);
+Long enumValue = val.jvmValue(Long.class);
  if (enumValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/FieldEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldRules;
 import build.buf.validate.Ignore;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -95,7 +94,7 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreAlways()) {
  return RuleViolation.NO_VIOLATIONS;
  }
-Message message = val.messageValue();
+MessageReflector message = val.messageValue();
  if (message == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
@@ -113,17 +112,19 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreEmpty() && !hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
- return valueEvaluator.evaluate(
- new ObjectValue(descriptor, message.getField(descriptor)), failFast);
+ return valueEvaluator.evaluate(message.getField(descriptor), failFast);
  }
 
  /**
  * Returns whether the given field is set on the message. Handles repeated and map fields, which
- * are not supported by {@link Message#hasField}.
+ * require inspecting the list/map contents rather than a presence bit.
  */
- static boolean isFieldSet(Message message, FieldDescriptor field) {
+ static boolean isFieldSet(MessageReflector message, FieldDescriptor field) {
  if (field.isRepeated()) {
- return message.getRepeatedFieldCount(field) != 0;
+ if (field.isMapField()) {
+ return !message.getField(field).mapValue().isEmpty();
+ }
+ return !message.getField(field).repeatedValue().isEmpty();
  }
  return message.hasField(field);
  }

src/main/java/build/buf/protovalidate/ListElementValue.java

@@ -45,15 +45,20 @@ final class ListElementValue implements Value {
  }
 
  @Override
- public @Nullable Message messageValue() {
+ public @Nullable MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.scalarToCel(fieldDescriptor.getType(), value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
  Descriptors.FieldDescriptor.Type type = fieldDescriptor.getType();
  if (type == Descriptors.FieldDescriptor.Type.MESSAGE) {
  return clazz.cast(value);

src/main/java/build/buf/protovalidate/MapEvaluator.java

@@ -155,19 +155,19 @@ private List<RuleViolation.Builder> evalPairs(Value key, Value value, boolean fa
  case TYPE_SINT64:
  case TYPE_SFIXED32:
  case TYPE_SFIXED64:
- fieldPathElementBuilder.setIntKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setIntKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_UINT32:
  case TYPE_UINT64:
  case TYPE_FIXED32:
  case TYPE_FIXED64:
- fieldPathElementBuilder.setUintKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setUintKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_BOOL:
- fieldPathElementBuilder.setBoolKey(key.value(Boolean.class));
+ fieldPathElementBuilder.setBoolKey(key.jvmValue(Boolean.class));
  break;
  case TYPE_STRING:
- fieldPathElementBuilder.setStringKey(key.value(String.class));
+ fieldPathElementBuilder.setStringKey(key.jvmValue(String.class));
  break;
  default:
  throw new ExecutionException("Unexpected map key type");

src/main/java/build/buf/protovalidate/MessageOneofEvaluator.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message msg = val.messageValue();
+MessageReflector msg = val.messageValue();
  if (msg == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/MessageReflector.java

@@ -0,0 +1,59 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+/**
+ * {@link MessageReflector} is a wrapper around a protobuf message that provides reflective access
+ * to the underlying message.
+ *
+ * <p>{@link MessageReflector} is a runtime-independent interface. Any protobuf runtime that
+ * implements this interface can wrap its messages so that protovalidate-java can validate them.
+ */
+public interface MessageReflector {
+ /**
+ * The {@link Descriptor} of the wrapped message's type.
+ *
+ * @return The descriptor.
+ */
+ Descriptor getDescriptorForType();
+
+ /**
+ * Whether the wrapped message has the field described by the provided field descriptor.
+ *
+ * @param field The field descriptor to check for.
+ * @return Whether the field is present.
+ */
+ boolean hasField(FieldDescriptor field);
+
+ /**
+ * Get the value described by the provided field descriptor.
+ *
+ * @param field The field descriptor for which to retrieve a value.
+ * @return The value corresponding to the field descriptor.
+ */
+ Value getField(FieldDescriptor field);
+
+ /**
+ * Returns the representation of this message to hand to CEL for {@code this}-variable rule
+ * evaluation. Implementations return whichever form CEL can navigate for their runtime, such as
+ * a {@link com.google.protobuf.Message} or a {@code dev.cel.common.values.CelValue}.
+ *
+ * @return The CEL-navigable representation of this message.
+ */
+ Object celValue();
+}

src/main/java/build/buf/protovalidate/MessageReflectorValue.java

@@ -0,0 +1,66 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import org.jspecify.annotations.Nullable;
+
+/** Top-level {@link Value} backed by a user-supplied {@link MessageReflector}. */
+final class MessageReflectorValue implements Value {
+
+ private final MessageReflector reflector;
+
+ MessageReflectorValue(MessageReflector reflector) {
+ this.reflector = reflector;
+ }
+
+ @Override
+ public Descriptors.@Nullable FieldDescriptor fieldDescriptor() {
+ return null;
+ }
+
+ @Override
+ public MessageReflector messageValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object rawValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object celValue() {
+ return reflector.celValue();
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public List<Value> repeatedValue() {
+ return Collections.emptyList();
+ }
+
+ @Override
+ public Map<Value, Value> mapValue() {
+ return Collections.emptyMap();
+ }
+}

src/main/java/build/buf/protovalidate/MessageValue.java

@@ -24,16 +24,15 @@
 /** The {@link Value} type that contains a {@link com.google.protobuf.Message}. */
 final class MessageValue implements Value {
 
- /** Object type since the object type is inferred from the field descriptor. */
- private final Object value;
+ private final ProtobufMessageReflector value;
 
  /**
  * Constructs a {@link MessageValue} with the provided message value.
  *
  * @param value The message value.
  */
  MessageValue(Message value) {
- this.value = value;
+ this.value = new ProtobufMessageReflector(value);
  }
 
  @Override
@@ -42,13 +41,18 @@ final class MessageValue implements Value {
  }
 
  @Override
- public Message messageValue() {
- return (Message) value;
+ public MessageReflector messageValue() {
+ return value;
+ }
+
+ @Override
+ public Object celValue() {
+ return value.getMessage();
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
-return clazz.cast(value);
+ public <T> T jvmValue(Class<T> clazz) {
+throw new UnsupportedOperationException();
  }
 
  @Override

src/main/java/build/buf/protovalidate/ObjectValue.java

@@ -53,15 +53,23 @@ public Descriptors.FieldDescriptor fieldDescriptor() {
 
  @Nullable
  @Override
- public Message messageValue() {
+ public MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.toCel(fieldDescriptor, value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ if (value instanceof Descriptors.EnumValueDescriptor) {
+ return clazz.cast((long) ((Descriptors.EnumValueDescriptor) value).getNumber());
+ }
  return clazz.cast(ProtoAdapter.toCel(fieldDescriptor, value));
  }
 

src/main/java/build/buf/protovalidate/OneofEvaluator.java

@@ -17,7 +17,6 @@
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.FieldPathElement;
 import com.google.protobuf.Descriptors.OneofDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -48,8 +47,12 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- Message message = val.messageValue();
- if (message == null || !required || (message.getOneofFieldDescriptor(descriptor) != null)) {
+ MessageReflector message = val.messageValue();
+ if (message == null) {
+ return RuleViolation.NO_VIOLATIONS;
+ }
+ boolean hasField = descriptor.getFields().stream().anyMatch(message::hasField);
+ if (!required || hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
  return Collections.singletonList(

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 assertj = "3.27.7"
 buf = "1.70.0"
-cel = "0.13.0"
+cel = "0.13.1"
 error-prone = "2.49.0"
 junit = "5.14.4"
 maven-publish = "0.36.0"

src/main/java/build/buf/protovalidate/AnyEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldPath;
 import build.buf.validate.FieldRules;
 import com.google.protobuf.Descriptors;
-import com.google.protobuf.Message;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -78,12 +77,12 @@ final class AnyEvaluator implements Evaluator {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message anyValue = val.messageValue();
+MessageReflector anyValue = val.messageValue();
  if (anyValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
  List<RuleViolation.Builder> violationList = new ArrayList<>();
- String typeURL = (String) anyValue.getField(typeURLDescriptor);
+ String typeURL = anyValue.getField(typeURLDescriptor).jvmValue(String.class);
  if (!in.isEmpty() && !in.contains(typeURL)) {
  RuleViolation.Builder violation =
  RuleViolation.newBuilder()

src/main/java/build/buf/protovalidate/CelPrograms.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- CelVariableResolver bindings = Variable.newThisVariable(val.value(Object.class));
+ CelVariableResolver bindings = Variable.newThisVariable(val.celValue());
  List<RuleViolation.Builder> violations = new ArrayList<>();
  for (CompiledProgram program : programs) {
  RuleViolation.Builder violation = program.eval(val, bindings);

src/main/java/build/buf/protovalidate/EnumEvaluator.java

@@ -77,7 +77,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Object enumValue = val.value(Object.class);
+Long enumValue = val.jvmValue(Long.class);
  if (enumValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/FieldEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldRules;
 import build.buf.validate.Ignore;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -95,7 +94,7 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreAlways()) {
  return RuleViolation.NO_VIOLATIONS;
  }
-Message message = val.messageValue();
+MessageReflector message = val.messageValue();
  if (message == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
@@ -113,17 +112,19 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreEmpty() && !hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
- return valueEvaluator.evaluate(
- new ObjectValue(descriptor, message.getField(descriptor)), failFast);
+ return valueEvaluator.evaluate(message.getField(descriptor), failFast);
  }
 
  /**
  * Returns whether the given field is set on the message. Handles repeated and map fields, which
- * are not supported by {@link Message#hasField}.
+ * require inspecting the list/map contents rather than a presence bit.
  */
- static boolean isFieldSet(Message message, FieldDescriptor field) {
+ static boolean isFieldSet(MessageReflector message, FieldDescriptor field) {
  if (field.isRepeated()) {
- return message.getRepeatedFieldCount(field) != 0;
+ if (field.isMapField()) {
+ return !message.getField(field).mapValue().isEmpty();
+ }
+ return !message.getField(field).repeatedValue().isEmpty();
  }
  return message.hasField(field);
  }

src/main/java/build/buf/protovalidate/ListElementValue.java

@@ -45,15 +45,20 @@ final class ListElementValue implements Value {
  }
 
  @Override
- public @Nullable Message messageValue() {
+ public @Nullable MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.scalarToCel(fieldDescriptor.getType(), value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
  Descriptors.FieldDescriptor.Type type = fieldDescriptor.getType();
  if (type == Descriptors.FieldDescriptor.Type.MESSAGE) {
  return clazz.cast(value);

src/main/java/build/buf/protovalidate/MapEvaluator.java

@@ -155,19 +155,19 @@ private List<RuleViolation.Builder> evalPairs(Value key, Value value, boolean fa
  case TYPE_SINT64:
  case TYPE_SFIXED32:
  case TYPE_SFIXED64:
- fieldPathElementBuilder.setIntKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setIntKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_UINT32:
  case TYPE_UINT64:
  case TYPE_FIXED32:
  case TYPE_FIXED64:
- fieldPathElementBuilder.setUintKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setUintKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_BOOL:
- fieldPathElementBuilder.setBoolKey(key.value(Boolean.class));
+ fieldPathElementBuilder.setBoolKey(key.jvmValue(Boolean.class));
  break;
  case TYPE_STRING:
- fieldPathElementBuilder.setStringKey(key.value(String.class));
+ fieldPathElementBuilder.setStringKey(key.jvmValue(String.class));
  break;
  default:
  throw new ExecutionException("Unexpected map key type");

src/main/java/build/buf/protovalidate/MessageOneofEvaluator.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message msg = val.messageValue();
+MessageReflector msg = val.messageValue();
  if (msg == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/MessageReflector.java

@@ -0,0 +1,59 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+/**
+ * {@link MessageReflector} is a wrapper around a protobuf message that provides reflective access
+ * to the underlying message.
+ *
+ * <p>{@link MessageReflector} is a runtime-independent interface. Any protobuf runtime that
+ * implements this interface can wrap its messages so that protovalidate-java can validate them.
+ */
+public interface MessageReflector {
+ /**
+ * The {@link Descriptor} of the wrapped message's type.
+ *
+ * @return The descriptor.
+ */
+ Descriptor getDescriptorForType();
+
+ /**
+ * Whether the wrapped message has the field described by the provided field descriptor.
+ *
+ * @param field The field descriptor to check for.
+ * @return Whether the field is present.
+ */
+ boolean hasField(FieldDescriptor field);
+
+ /**
+ * Get the value described by the provided field descriptor.
+ *
+ * @param field The field descriptor for which to retrieve a value.
+ * @return The value corresponding to the field descriptor.
+ */
+ Value getField(FieldDescriptor field);
+
+ /**
+ * Returns the representation of this message to hand to CEL for {@code this}-variable rule
+ * evaluation. Implementations return whichever form CEL can navigate for their runtime, such as
+ * a {@link com.google.protobuf.Message} or a {@code dev.cel.common.values.CelValue}.
+ *
+ * @return The CEL-navigable representation of this message.
+ */
+ Object celValue();
+}

src/main/java/build/buf/protovalidate/MessageReflectorValue.java

@@ -0,0 +1,66 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import org.jspecify.annotations.Nullable;
+
+/** Top-level {@link Value} backed by a user-supplied {@link MessageReflector}. */
+final class MessageReflectorValue implements Value {
+
+ private final MessageReflector reflector;
+
+ MessageReflectorValue(MessageReflector reflector) {
+ this.reflector = reflector;
+ }
+
+ @Override
+ public Descriptors.@Nullable FieldDescriptor fieldDescriptor() {
+ return null;
+ }
+
+ @Override
+ public MessageReflector messageValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object rawValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object celValue() {
+ return reflector.celValue();
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public List<Value> repeatedValue() {
+ return Collections.emptyList();
+ }
+
+ @Override
+ public Map<Value, Value> mapValue() {
+ return Collections.emptyMap();
+ }
+}

src/main/java/build/buf/protovalidate/MessageValue.java

@@ -24,16 +24,15 @@
 /** The {@link Value} type that contains a {@link com.google.protobuf.Message}. */
 final class MessageValue implements Value {
 
- /** Object type since the object type is inferred from the field descriptor. */
- private final Object value;
+ private final ProtobufMessageReflector value;
 
  /**
  * Constructs a {@link MessageValue} with the provided message value.
  *
  * @param value The message value.
  */
  MessageValue(Message value) {
- this.value = value;
+ this.value = new ProtobufMessageReflector(value);
  }
 
  @Override
@@ -42,13 +41,18 @@ final class MessageValue implements Value {
  }
 
  @Override
- public Message messageValue() {
- return (Message) value;
+ public MessageReflector messageValue() {
+ return value;
+ }
+
+ @Override
+ public Object celValue() {
+ return value.getMessage();
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
-return clazz.cast(value);
+ public <T> T jvmValue(Class<T> clazz) {
+throw new UnsupportedOperationException();
  }
 
  @Override

src/main/java/build/buf/protovalidate/ObjectValue.java

@@ -53,15 +53,23 @@ public Descriptors.FieldDescriptor fieldDescriptor() {
 
  @Nullable
  @Override
- public Message messageValue() {
+ public MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.toCel(fieldDescriptor, value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ if (value instanceof Descriptors.EnumValueDescriptor) {
+ return clazz.cast((long) ((Descriptors.EnumValueDescriptor) value).getNumber());
+ }
  return clazz.cast(ProtoAdapter.toCel(fieldDescriptor, value));
  }
 

src/main/java/build/buf/protovalidate/OneofEvaluator.java

@@ -17,7 +17,6 @@
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.FieldPathElement;
 import com.google.protobuf.Descriptors.OneofDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -48,8 +47,12 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- Message message = val.messageValue();
- if (message == null || !required || (message.getOneofFieldDescriptor(descriptor) != null)) {
+ MessageReflector message = val.messageValue();
+ if (message == null) {
+ return RuleViolation.NO_VIOLATIONS;
+ }
+ boolean hasField = descriptor.getFields().stream().anyMatch(message::hasField);
+ if (!required || hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
  return Collections.singletonList(

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 assertj = "3.27.7"
 buf = "1.70.0"
-cel = "0.13.0"
+cel = "0.13.1"
 error-prone = "2.49.0"
 junit = "5.14.4"
 maven-publish = "0.36.0"

src/main/java/build/buf/protovalidate/AnyEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldPath;
 import build.buf.validate.FieldRules;
 import com.google.protobuf.Descriptors;
-import com.google.protobuf.Message;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.HashSet;
@@ -78,12 +77,12 @@ final class AnyEvaluator implements Evaluator {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message anyValue = val.messageValue();
+MessageReflector anyValue = val.messageValue();
  if (anyValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
  List<RuleViolation.Builder> violationList = new ArrayList<>();
- String typeURL = (String) anyValue.getField(typeURLDescriptor);
+ String typeURL = anyValue.getField(typeURLDescriptor).jvmValue(String.class);
  if (!in.isEmpty() && !in.contains(typeURL)) {
  RuleViolation.Builder violation =
  RuleViolation.newBuilder()

src/main/java/build/buf/protovalidate/CelPrograms.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- CelVariableResolver bindings = Variable.newThisVariable(val.value(Object.class));
+ CelVariableResolver bindings = Variable.newThisVariable(val.celValue());
  List<RuleViolation.Builder> violations = new ArrayList<>();
  for (CompiledProgram program : programs) {
  RuleViolation.Builder violation = program.eval(val, bindings);

src/main/java/build/buf/protovalidate/EnumEvaluator.java

@@ -77,7 +77,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Object enumValue = val.value(Object.class);
+Long enumValue = val.jvmValue(Long.class);
  if (enumValue == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/FieldEvaluator.java

@@ -19,7 +19,6 @@
 import build.buf.validate.FieldRules;
 import build.buf.validate.Ignore;
 import com.google.protobuf.Descriptors.FieldDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -95,7 +94,7 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreAlways()) {
  return RuleViolation.NO_VIOLATIONS;
  }
-Message message = val.messageValue();
+MessageReflector message = val.messageValue();
  if (message == null) {
  return RuleViolation.NO_VIOLATIONS;
  }
@@ -113,17 +112,19 @@ public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  if (this.shouldIgnoreEmpty() && !hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
- return valueEvaluator.evaluate(
- new ObjectValue(descriptor, message.getField(descriptor)), failFast);
+ return valueEvaluator.evaluate(message.getField(descriptor), failFast);
  }
 
  /**
  * Returns whether the given field is set on the message. Handles repeated and map fields, which
- * are not supported by {@link Message#hasField}.
+ * require inspecting the list/map contents rather than a presence bit.
  */
- static boolean isFieldSet(Message message, FieldDescriptor field) {
+ static boolean isFieldSet(MessageReflector message, FieldDescriptor field) {
  if (field.isRepeated()) {
- return message.getRepeatedFieldCount(field) != 0;
+ if (field.isMapField()) {
+ return !message.getField(field).mapValue().isEmpty();
+ }
+ return !message.getField(field).repeatedValue().isEmpty();
  }
  return message.hasField(field);
  }

src/main/java/build/buf/protovalidate/ListElementValue.java

@@ -45,15 +45,20 @@ final class ListElementValue implements Value {
  }
 
  @Override
- public @Nullable Message messageValue() {
+ public @Nullable MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.scalarToCel(fieldDescriptor.getType(), value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
  Descriptors.FieldDescriptor.Type type = fieldDescriptor.getType();
  if (type == Descriptors.FieldDescriptor.Type.MESSAGE) {
  return clazz.cast(value);

src/main/java/build/buf/protovalidate/MapEvaluator.java

@@ -155,19 +155,19 @@ private List<RuleViolation.Builder> evalPairs(Value key, Value value, boolean fa
  case TYPE_SINT64:
  case TYPE_SFIXED32:
  case TYPE_SFIXED64:
- fieldPathElementBuilder.setIntKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setIntKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_UINT32:
  case TYPE_UINT64:
  case TYPE_FIXED32:
  case TYPE_FIXED64:
- fieldPathElementBuilder.setUintKey(key.value(Number.class).longValue());
+ fieldPathElementBuilder.setUintKey(key.jvmValue(Number.class).longValue());
  break;
  case TYPE_BOOL:
- fieldPathElementBuilder.setBoolKey(key.value(Boolean.class));
+ fieldPathElementBuilder.setBoolKey(key.jvmValue(Boolean.class));
  break;
  case TYPE_STRING:
- fieldPathElementBuilder.setStringKey(key.value(String.class));
+ fieldPathElementBuilder.setStringKey(key.jvmValue(String.class));
  break;
  default:
  throw new ExecutionException("Unexpected map key type");

src/main/java/build/buf/protovalidate/MessageOneofEvaluator.java

@@ -45,7 +45,7 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
-Message msg = val.messageValue();
+MessageReflector msg = val.messageValue();
  if (msg == null) {
  return RuleViolation.NO_VIOLATIONS;
  }

src/main/java/build/buf/protovalidate/MessageReflector.java

@@ -0,0 +1,59 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors.Descriptor;
+import com.google.protobuf.Descriptors.FieldDescriptor;
+
+/**
+ * {@link MessageReflector} is a wrapper around a protobuf message that provides reflective access
+ * to the underlying message.
+ *
+ * <p>{@link MessageReflector} is a runtime-independent interface. Any protobuf runtime that
+ * implements this interface can wrap its messages so that protovalidate-java can validate them.
+ */
+public interface MessageReflector {
+ /**
+ * The {@link Descriptor} of the wrapped message's type.
+ *
+ * @return The descriptor.
+ */
+ Descriptor getDescriptorForType();
+
+ /**
+ * Whether the wrapped message has the field described by the provided field descriptor.
+ *
+ * @param field The field descriptor to check for.
+ * @return Whether the field is present.
+ */
+ boolean hasField(FieldDescriptor field);
+
+ /**
+ * Get the value described by the provided field descriptor.
+ *
+ * @param field The field descriptor for which to retrieve a value.
+ * @return The value corresponding to the field descriptor.
+ */
+ Value getField(FieldDescriptor field);
+
+ /**
+ * Returns the representation of this message to hand to CEL for {@code this}-variable rule
+ * evaluation. Implementations return whichever form CEL can navigate for their runtime, such as
+ * a {@link com.google.protobuf.Message} or a {@code dev.cel.common.values.CelValue}.
+ *
+ * @return The CEL-navigable representation of this message.
+ */
+ Object celValue();
+}

src/main/java/build/buf/protovalidate/MessageReflectorValue.java

@@ -0,0 +1,66 @@
+// Copyright 2023-2026 Buf Technologies, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build.buf.protovalidate;
+
+import com.google.protobuf.Descriptors;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import org.jspecify.annotations.Nullable;
+
+/** Top-level {@link Value} backed by a user-supplied {@link MessageReflector}. */
+final class MessageReflectorValue implements Value {
+
+ private final MessageReflector reflector;
+
+ MessageReflectorValue(MessageReflector reflector) {
+ this.reflector = reflector;
+ }
+
+ @Override
+ public Descriptors.@Nullable FieldDescriptor fieldDescriptor() {
+ return null;
+ }
+
+ @Override
+ public MessageReflector messageValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object rawValue() {
+ return reflector;
+ }
+
+ @Override
+ public Object celValue() {
+ return reflector.celValue();
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ throw new UnsupportedOperationException();
+ }
+
+ @Override
+ public List<Value> repeatedValue() {
+ return Collections.emptyList();
+ }
+
+ @Override
+ public Map<Value, Value> mapValue() {
+ return Collections.emptyMap();
+ }
+}

src/main/java/build/buf/protovalidate/MessageValue.java

@@ -24,16 +24,15 @@
 /** The {@link Value} type that contains a {@link com.google.protobuf.Message}. */
 final class MessageValue implements Value {
 
- /** Object type since the object type is inferred from the field descriptor. */
- private final Object value;
+ private final ProtobufMessageReflector value;
 
  /**
  * Constructs a {@link MessageValue} with the provided message value.
  *
  * @param value The message value.
  */
  MessageValue(Message value) {
- this.value = value;
+ this.value = new ProtobufMessageReflector(value);
  }
 
  @Override
@@ -42,13 +41,18 @@ final class MessageValue implements Value {
  }
 
  @Override
- public Message messageValue() {
- return (Message) value;
+ public MessageReflector messageValue() {
+ return value;
+ }
+
+ @Override
+ public Object celValue() {
+ return value.getMessage();
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
-return clazz.cast(value);
+ public <T> T jvmValue(Class<T> clazz) {
+throw new UnsupportedOperationException();
  }
 
  @Override

src/main/java/build/buf/protovalidate/ObjectValue.java

@@ -53,15 +53,23 @@ public Descriptors.FieldDescriptor fieldDescriptor() {
 
  @Nullable
  @Override
- public Message messageValue() {
+ public MessageReflector messageValue() {
  if (fieldDescriptor.getJavaType() == Descriptors.FieldDescriptor.JavaType.MESSAGE) {
- return (Message) value;
+ return new ProtobufMessageReflector((Message) value);
  }
  return null;
  }
 
  @Override
- public <T> T value(Class<T> clazz) {
+ public Object celValue() {
+ return ProtoAdapter.toCel(fieldDescriptor, value);
+ }
+
+ @Override
+ public <T> T jvmValue(Class<T> clazz) {
+ if (value instanceof Descriptors.EnumValueDescriptor) {
+ return clazz.cast((long) ((Descriptors.EnumValueDescriptor) value).getNumber());
+ }
  return clazz.cast(ProtoAdapter.toCel(fieldDescriptor, value));
  }
 

src/main/java/build/buf/protovalidate/OneofEvaluator.java

@@ -17,7 +17,6 @@
 import build.buf.protovalidate.exceptions.ExecutionException;
 import build.buf.validate.FieldPathElement;
 import com.google.protobuf.Descriptors.OneofDescriptor;
-import com.google.protobuf.Message;
 import java.util.Collections;
 import java.util.List;
 
@@ -48,8 +47,12 @@ public boolean tautology() {
  @Override
  public List<RuleViolation.Builder> evaluate(Value val, boolean failFast)
  throws ExecutionException {
- Message message = val.messageValue();
- if (message == null || !required || (message.getOneofFieldDescriptor(descriptor) != null)) {
+ MessageReflector message = val.messageValue();
+ if (message == null) {
+ return RuleViolation.NO_VIOLATIONS;
+ }
+ boolean hasField = descriptor.getFields().stream().anyMatch(message::hasField);
+ if (!required || hasField) {
  return RuleViolation.NO_VIOLATIONS;
  }
  return Collections.singletonList(