INT-2622: add JMX support for DelayerHandler

* introduce DelayHandlerManagement
* add GroovyControlBusIntegrationTests
* test for Delayer Management via Groovy Control Bus

spring-integration-core/src/main/java/org/springframework/integration/handler/DelayHandler.java

@@ -30,6 +30,7 @@ import org.springframework.integration.store.MessageGroupStore;
 import org.springframework.integration.store.MessageStore;
 import org.springframework.integration.store.SimpleMessageStore;
 import org.springframework.integration.support.MessageBuilder;
+import org.springframework.jmx.export.annotation.ManagedResource;
 import org.springframework.scheduling.TaskScheduler;
 import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
 import org.springframework.util.Assert;
@@ -62,7 +63,9 @@ import org.springframework.util.Assert;
  * @author Artem Bilan
  * @since 1.0.3
  */
-public class DelayHandler extends AbstractReplyProducingMessageHandler implements ApplicationListener<ContextRefreshedEvent> {
+
+@ManagedResource
+public class DelayHandler extends AbstractReplyProducingMessageHandler implements DelayHandlerManagement, ApplicationListener<ContextRefreshedEvent> {
 
 	private final String messageGroupId;
 
@@ -226,6 +229,10 @@ public class DelayHandler extends AbstractReplyProducingMessageHandler implement
 		}
 	}
 
+	public int getDelayedMessageCount() {
+		return this.messageStore.messageGroupSize(this.messageGroupId);
+	}
+
 	/**
 	 * Used for reading persisted Messages in the 'messageStore'
 	 * to reschedule them e.g. upon application restart.

spring-integration-core/src/main/java/org/springframework/integration/handler/DelayHandlerManagement.java

@@ -0,0 +1,31 @@
+/*
+ * Copyright 2002-2012 the original author or authors.
+ *
+ * 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 org.springframework.integration.handler;
+
+import org.springframework.jmx.export.annotation.ManagedAttribute;
+import org.springframework.jmx.export.annotation.ManagedOperation;
+
+/**
+ * @author Artem Bilan
+ * @since 2.2
+ */
+
+public interface DelayHandlerManagement {
+
+	@ManagedAttribute
+	int getDelayedMessageCount();
+
+	@ManagedOperation
+	void reschedulePersistedMessages();
+}