added the client side and a test case to show prefetch of zero working for pull-only queues with synchronous consumers to fix AMQ-855

git-svn-id: https://svn.apache.org/repos/asf/incubator/activemq/trunk@430476 13f79535-47bb-0310-9956-ffa450edef68

activemq-core/src/main/java/org/apache/activemq/ActiveMQMessageConsumer.java

@@ -34,6 +34,7 @@ import org.apache.activemq.command.ConsumerId;
 import org.apache.activemq.command.ConsumerInfo;
 import org.apache.activemq.command.MessageAck;
 import org.apache.activemq.command.MessageDispatch;
+import org.apache.activemq.command.MessagePull;
 import org.apache.activemq.management.JMSConsumerStatsImpl;
 import org.apache.activemq.management.StatsCapable;
 import org.apache.activemq.management.StatsImpl;
@@ -323,6 +324,9 @@ public class ActiveMQMessageConsumer implements MessageAvailableConsumer, StatsC
      */
     public void setMessageListener(MessageListener listener) throws JMSException {
         checkClosed();
+        if (info.getPrefetchSize() == 0) {
+            throw new JMSException("Illegal prefetch size of zero. This setting is not supported for asynchronous consumers please set a value of at least 1");
+        }
         this.messageListener = listener;
         if (listener != null) {
             boolean wasRunning = session.isRunning();
@@ -411,6 +415,7 @@ public class ActiveMQMessageConsumer implements MessageAvailableConsumer, StatsC
      *         this message consumer is concurrently closed
      */
     public Message receive() throws JMSException {
+        sendPullCommand();
         checkClosed();
         checkMessageListener();
         MessageDispatch md = dequeue(-1);
@@ -455,6 +460,7 @@ public class ActiveMQMessageConsumer implements MessageAvailableConsumer, StatsC
      *         closed
      */
     public Message receive(long timeout) throws JMSException {
+        sendPullCommand();
         checkClosed();
         checkMessageListener();
         if (timeout == 0) {
@@ -587,6 +593,19 @@ public class ActiveMQMessageConsumer implements MessageAvailableConsumer, StatsC
         }
     }
     
+    /**
+     * If we have a zero prefetch specified then send a pull command to the broker to pull a message
+     * we are about to receive
+     *
+     */
+    protected void sendPullCommand() throws JMSException {
+        if (info.getPrefetchSize() == 0) {
+            MessagePull messagePull = new MessagePull();
+            messagePull.configure(info);
+            session.asyncSendPacket(messagePull);
+        }
+    }
+
     protected void checkMessageListener() throws JMSException {
         session.checkMessageListener();
     }

activemq-core/src/main/java/org/apache/activemq/MessageDispatchChannel.java

@@ -163,6 +163,8 @@ public class MessageDispatchChannel {
     }
 
     public String toString() {
+        synchronized(mutex) {
             return list.toString();
         }
     }
+}

activemq-core/src/main/java/org/apache/activemq/command/MessagePull.java

@@ -42,6 +42,14 @@ public class MessagePull extends BaseCommand {
         return visitor.processMessagePull(this);
     }
 
+    /**
+     * Configures a message pull from the consumer information
+     */
+    public void configure(ConsumerInfo info) {
+        setConsumerId(info.getConsumerId());
+        setDestination(info.getDestination());
+    }
+
     /**
      * @openwire:property version=1 cache=true
      */

activemq-core/src/test/java/org/apache/activemq/ZeroPrefetchConsumerTest.java

@@ -0,0 +1,88 @@
+/**
+ *
+ * Copyright 2005-2006 The Apache Software Foundation
+ *
+ * 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.apache.activemq;
+
+import org.apache.activemq.command.ActiveMQQueue;
+import org.apache.activemq.spring.SpringConsumer;
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
+
+import javax.jms.Connection;
+import javax.jms.JMSException;
+import javax.jms.Message;
+import javax.jms.MessageConsumer;
+import javax.jms.MessageListener;
+import javax.jms.MessageProducer;
+import javax.jms.Queue;
+import javax.jms.Session;
+
+/**
+ * 
+ * @version $Revision$
+ */
+public class ZeroPrefetchConsumerTest extends TestSupport {
+
+    private static final Log log = LogFactory.getLog(ZeroPrefetchConsumerTest.class);
+
+    protected Connection connection;
+    protected Queue queue;
+
+    public void testCannotUseMessageListener() throws Exception {
+        Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
+        MessageConsumer consumer = session.createConsumer(queue);
+
+        MessageListener listener = new SpringConsumer();
+        try {
+            consumer.setMessageListener(listener);
+            fail("Should have thrown JMSException as we cannot use MessageListener with zero prefetch");
+        }
+        catch (JMSException e) {
+            log.info("Received expected exception : " + e);
+        }
+    }
+
+    public void testPullConsumerWorks() throws Exception {
+        Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);
+
+        MessageProducer producer = session.createProducer(queue);
+        producer.send(session.createTextMessage("Hello World!"));
+        
+        // now lets receive it
+        MessageConsumer consumer = session.createConsumer(queue);
+        Message answer = consumer.receive(5000);
+        assertNotNull("Should have received a message!", answer);
+    }
+
+    protected void setUp() throws Exception {
+        topic = false;
+        super.setUp();
+
+        connection = createConnection();
+        connection.start();
+        queue = createQueue();
+    }
+
+    protected void tearDown() throws Exception {
+        connection.close();
+        super.tearDown();
+    }
+
+    protected Queue createQueue() {
+        return new ActiveMQQueue(getClass().getName() + "." + getName() + "?consumer.prefetchSize=0");
+    }
+
+}