Polish JMS observation instrumentation

See gh-30335
Closes gh-31172

Author: izeye

framework-docs/modules/ROOT/pages/integration/observability.adoc

@@ -176,7 +176,7 @@ but note that `@JmsListener` annotations can refer to specific container factory
 In all cases, Observations are only recorded if the observation registry is configured on the container factory.
 
 Similar observations are recorded with `JmsTemplate` when messages are processed by a `MessageListener`.
-Such listeners are set on a  `MessageConsumer` within a session callback (see `JmsTemplate.execute(SessionCallback<T>)`).
+Such listeners are set on a `MessageConsumer` within a session callback (see `JmsTemplate.execute(SessionCallback<T>)`).
 
 This observation uses the `io.micrometer.core.instrument.binder.jms.DefaultJmsProcessObservationConvention` by default, backed by the `io.micrometer.core.instrument.binder.jms.JmsProcessObservationContext`.
 

spring-jms/src/main/java/org/springframework/jms/config/AbstractJmsListenerContainerFactory.java

@@ -198,6 +198,10 @@ public void setAutoStartup(boolean autoStartup) {
 	}
 
 	/**
+	 * Set the {@link ObservationRegistry} to be used for recording
+	 * {@link io.micrometer.core.instrument.binder.jms.JmsObservationDocumentation#JMS_MESSAGE_PROCESS JMS message processing observations}.
+	 * Defaults to no-op observations if the registry is not set.
+	 * @since 6.1
 	 * @see AbstractMessageListenerContainer#setObservationRegistry(ObservationRegistry)
 	 */
 	public void setObservationRegistry(ObservationRegistry observationRegistry) {

spring-jms/src/main/java/org/springframework/jms/listener/AbstractMessageListenerContainer.java

@@ -577,7 +577,7 @@ public ErrorHandler getErrorHandler() {
 
 	/**
 	 * Return the {@link ObservationRegistry} used for recording
-	 * {@link JmsObservationDocumentation#JMS_MESSAGE_PUBLISH JMS message processing observations}.
+	 * {@link JmsObservationDocumentation#JMS_MESSAGE_PROCESS JMS message processing observations}.
 	 * @since 6.1
 	 */
 	@Nullable
@@ -587,7 +587,7 @@ public ObservationRegistry getObservationRegistry() {
 
 	/**
 	 * Set the {@link ObservationRegistry} to be used for recording
-	 * {@link JmsObservationDocumentation#JMS_MESSAGE_PUBLISH JMS message processing observations}.
+	 * {@link JmsObservationDocumentation#JMS_MESSAGE_PROCESS JMS message processing observations}.
 	 * Defaults to no-op observations if the registry is not set.
 	 * @since 6.1
 	 */
@@ -716,7 +716,7 @@ protected void doExecuteListener(Session session, Message message) throws JMSExc
 	}
 
 	private Observation createObservation(Message message) {
-		if (micrometerCorePresent) {
+		if (micrometerCorePresent && this.observationRegistry != null) {
 			return ObservationFactory.create(this.observationRegistry, message);
 		}
 		else {
@@ -995,7 +995,7 @@ private static abstract class ObservationFactory {
 
 		private static final JmsProcessObservationConvention DEFAULT_CONVENTION = new DefaultJmsProcessObservationConvention();
 
-		static Observation create(@Nullable ObservationRegistry registry, Message message) {
+		static Observation create(ObservationRegistry registry, Message message) {
 			return JmsObservationDocumentation.JMS_MESSAGE_PROCESS
 					.observation(null, DEFAULT_CONVENTION, () -> new JmsProcessObservationContext(message), registry);
 		}