Make Client AutoCloseable and close() idempotent

- Make AutoClosable so it can be used in try-with-resources
- Removed null check for serverConnection since it cannot be null
- Do not shutdown serverConnection or close JAX-RS client if this client
is already closed.
Signed-off-by: Tony Germano <tony@germano.name>

Author: tonygermano

server/src/com/mirth/connect/client/core/Client.java

@@ -131,7 +131,11 @@
 importcom.mirth.connect.util.messagewriter.EncryptionType;
 importcom.mirth.connect.util.messagewriter.MessageWriterOptions;
 
-publicclassClientimplementsUserServletInterface, ConfigurationServletInterface, ChannelServletInterface, ChannelGroupServletInterface, ChannelStatusServletInterface, ChannelStatisticsServletInterface, EngineServletInterface, MessageServletInterface, EventServletInterface, AlertServletInterface, CodeTemplateServletInterface, DatabaseTaskServletInterface, UsageServletInterface, ExtensionServletInterface {
+publicclassClientimplementsUserServletInterface, ConfigurationServletInterface, ChannelServletInterface,
+ChannelGroupServletInterface, ChannelStatusServletInterface, ChannelStatisticsServletInterface,
+EngineServletInterface, MessageServletInterface, EventServletInterface, AlertServletInterface,
+CodeTemplateServletInterface, DatabaseTaskServletInterface, UsageServletInterface, ExtensionServletInterface,
+AutoCloseable {
 
 publicstaticfinalintMAX_QUERY_PARAM_COLLECTION_SIZE = 100;
 
@@ -312,9 +316,9 @@ public void setRecorder(InvocationHandlerRecorder recorder) {
 this.recorder = recorder;
  }
 
+@Override
 publicvoidclose() {
-closed.set(true);
-if (serverConnection != null) {
+if (!closed.getAndSet(true)) {
 serverConnection.shutdown();
 client.close();
  }
@@ -2675,4 +2679,4 @@ public void setPluginProperties(String extensionName, Properties properties, boo
 publicStringgetProperty(Stringgroup, Stringname) throwsClientException {
 returngetServlet(ConfigurationServletInterface.class).getProperty(group, name);
  }
-}
+}