added "boolean isRegisteredWithDestination()" method (SPR-7065)

jhoeller · jhoeller · commit 218ee6d24c99 · 2010-04-22T17:38:37.000Z
diff --git a/org.springframework.jms/src/main/java/org/springframework/jms/listener/DefaultMessageListenerContainer.java b/org.springframework.jms/src/main/java/org/springframework/jms/listener/DefaultMessageListenerContainer.java
@@ -178,6 +178,8 @@ public class DefaultMessageListenerContainer extends AbstractPollingMessageListe
 
 	private int activeInvokerCount = 0;
 
+	private int registeredWithDestination = 0;
+
 	private Runnable stopCallback;
 
 	private Object currentRecoveryMarker = new Object();
@@ -577,6 +579,27 @@ public final int getActiveConsumerCount() {
 		}
 	}
 
+	/**
+	 * Return whether at lease one consumer has entered a fixed registration with the
+	 * target destination. This is particularly interesting for the pub-sub case where
+	 * it might be important to have an actual consumer registered that is guaranteed
+	 * to not miss any messages that are just about to be published.
+	 * <p>This method may be polled after a {@link #start()} call, until asynchronous
+	 * registration of consumers has happened which is when the method will start returning
+	 * <code>true</code> - provided that the listener container actually ever establishes
+	 * a fixed registration. It will then keep returning <code>true</code> until shutdown,
+	 * since the container will hold on to at least one consumer registration thereafter.
+	 * <p>Note that a listener container is not bound to having a fixed registration in
+	 * the first place. It may also keep recreating consumers for every invoker execution.
+	 * This particularly depends on the {@link #setCacheLevel cache level} setting:
+	 * Only CACHE_CONSUMER will lead to a fixed registration.
+	 */
+	public boolean isRegisteredWithDestination() {
+		synchronized (this.lifecycleMonitor) {
+			return (this.registeredWithDestination > 0);
+		}
+	}
+
 
 	/**
 	 * Create a default TaskExecutor. Called if no explicit TaskExecutor has been specified.
@@ -1026,6 +1049,9 @@ private void initResourcesIfNecessary() throws JMSException {
 				}
 				if (this.consumer == null && getCacheLevel() >= CACHE_CONSUMER) {
 					this.consumer = createListenerConsumer(this.session);
+					synchronized (lifecycleMonitor) {
+						registeredWithDestination++;
+					}
 				}
 			}
 		}
@@ -1047,6 +1073,11 @@ private void clearResources() {
 				JmsUtils.closeMessageConsumer(this.consumer);
 				JmsUtils.closeSession(this.session);
 			}
+			if (this.consumer != null) {
+				synchronized (lifecycleMonitor) {
+					registeredWithDestination--;
+				}
+			}
 			this.consumer = null;
 			this.session = null;
 		}
