3. Code Examples

Here's a few code snippets showing how to access Kubernetes cluster using the library:

list all pods:

importio.kubernetes.client.openapi.ApiClient;
importio.kubernetes.client.openapi.ApiException;
importio.kubernetes.client.openapi.Configuration;
importio.kubernetes.client.openapi.apis.CoreV1Api;
importio.kubernetes.client.openapi.models.V1Pod;
importio.kubernetes.client.openapi.models.V1PodList;
importio.kubernetes.client.util.Config;
importjava.io.IOException;
publicclassExample {
publicstaticvoidmain(String[] args) throwsIOException, ApiException{
ApiClientclient = Config.defaultClient();
Configuration.setDefaultApiClient(client);
CoreV1Apiapi = newCoreV1Api();
V1PodListlist = api.listPodForAllNamespaces(null, null, null, null, null, null, null, null, null);
for (V1Poditem : list.getItems()) {
System.out.println(item.getMetadata().getName());
}
}
}

watch on namespace object:

importcom.google.gson.reflect.TypeToken;
importio.kubernetes.client.openapi.ApiClient;
importio.kubernetes.client.openapi.ApiException;
importio.kubernetes.client.openapi.Configuration;
importio.kubernetes.client.openapi.apis.CoreV1Api;
importio.kubernetes.client.openapi.models.V1Namespace;
importio.kubernetes.client.util.Config;
importio.kubernetes.client.util.Watch;
importjava.io.IOException;
publicclassWatchExample {
publicstaticvoidmain(String[] args) throwsIOException, ApiException{
ApiClientclient = Config.defaultClient();
Configuration.setDefaultApiClient(client);
CoreV1Apiapi = newCoreV1Api();
Watch<V1Namespace> watch = Watch.createWatch(
client,
api.listNamespaceCall(null, null, null, null, null, 5, null, null, Boolean.TRUE, null, null),
newTypeToken<Watch.Response<V1Namespace>>(){}.getType());
for (Watch.Response<V1Namespace> item : watch) {
System.out.printf("%s : %s%n", item.type, item.object.getMetadata().getName());
}
}
}

More examples can be found in examples folder. To run examples, run this command:

mvn exec:java -Dexec.mainClass="io.kubernetes.client.examples.Example"

Additionally, we prepared a few examples for common use-cases which are shown below:

• Configuration:
  • InClusterClientExample: Configure a client while running inside the Kubernetes cluster.
  • KubeConfigFileClientExample: Configure a client to access a Kubernetes cluster from outside.
• Basics:
  • SimpleExample: Simple minimum example of how to use the client.
  • ProtoExample: Request/receive payloads in protobuf serialization protocol.
  • PatchExample: Patch resource objects in various supported patch formats, equal to kubectl patch.
  • FluentExample: Construct arbitrary resource in a fluent builder style.
  • YamlExample: Suggested way to load or dump resource in Yaml.
• Streaming:
  • WatchExample: Subscribe watch events from certain resources, equal to kubectl get <resource> -w.
  • LogsExample: Fetch logs from running containers, equal to kubectl logs.
  • ExecExample: Establish an "exec" session with running containers, equal to kubectl exec.
  • PortForwardExample: Maps local port to a port on the pod, equal to kubectl port-forward.
  • AttachExample: Attach to a process that is already running inside an existing container, equal to kubectl attach.
  • CopyExample: Copy files and directories to and from containers, equal to kubectl cp.
  • WebSocketsExample: Establish an arbitrary web-socket session to certain resources.
• Advanced: (NOTE: The following example requires client-java-extended module）
  • (5.0.0+) InformerExample: Build an informer which list-watches resources and reflects the notifications to a local cache.
  • (5.0.0+) PagerExample: Support Pagination (only for the list request) to ease server-side loads/network congestion.
  • (6.0.0+) ControllerExample: Build a controller reconciling the state of world by list-watching one or multiple resources.
  • (6.0.0+) LeaderElectionExample: Leader election utilities to help implement HA controllers.
  • (9.0.0+) SpringIntegrationControllerExample: Building a kubernetes controller based on spring framework's bean injection, see additional documentation here.
  • (9.0.0+) GenericKubernetesClientExample: Construct a generic client interface for any kubernetes types, including CRDs.
  • (12.0.0+) DynamicKubernetesClientExample: Manipulating either native Kubernetes types or custom resources without generating classes.