'Version 1.0.4 of the Amazon SQS Java Messaging Library'

Author: robin-aws

README.md

@@ -15,7 +15,7 @@ for communicating with Amazon Simple Queue Service. This project builds on top o
   <dependency>
     <groupId>com.amazonaws</groupId>
     <artifactId>amazon-sqs-java-messaging-lib</artifactId>
-    <version>1.0.3</version>
+    <version>1.0.4</version>
     <type>jar</type>
   </dependency>
 ```

pom.xml

@@ -6,7 +6,7 @@
 
   <groupId>com.amazonaws</groupId>
   <artifactId>amazon-sqs-java-messaging-lib</artifactId>
-  <version>1.0.3</version>
+  <version>1.0.4</version>
   <packaging>jar</packaging>
   <name>Amazon SQS Java Messaging Library</name>
   <description>The Amazon SQS Java Messaging Library holds the Java Message Service compatible classes, that are used

src/main/java/com/amazon/sqs/javamessaging/PrefetchManager.java

@@ -27,6 +27,12 @@ public interface PrefetchManager {
      */
     public void messageDispatched();
 
+    /**
+     * Notify the prefetchThread that the message listener has finished with any
+     * previous message and is ready to accept another.
+     */
+    public void messageListenerReady();
+    
     /**
      * This is used to determine the state of the consumer, when the message
      * listener scheduler is processing the messages.

src/main/java/com/amazon/sqs/javamessaging/ProviderConfiguration.java

@@ -27,8 +27,8 @@ public int getNumberOfMessagesToPrefetch() {
     }
 
     public void setNumberOfMessagesToPrefetch(int numberOfMessagesToPrefetch) {
-        if (numberOfMessagesToPrefetch < SQSMessagingClientConstants.MIN_BATCH) {
-            throw new IllegalArgumentException(String.format("Invalid prefetch size. Provided value '%1$s' cannot be smaller than '%2$s'", numberOfMessagesToPrefetch, SQSMessagingClientConstants.MIN_BATCH));
+        if (numberOfMessagesToPrefetch < SQSMessagingClientConstants.MIN_PREFETCH) {
+            throw new IllegalArgumentException(String.format("Invalid prefetch size. Provided value '%1$s' cannot be smaller than '%2$s'", numberOfMessagesToPrefetch, SQSMessagingClientConstants.MIN_PREFETCH));
         }
         this.numberOfMessagesToPrefetch = numberOfMessagesToPrefetch;
     }

src/main/java/com/amazon/sqs/javamessaging/SQSConnection.java

@@ -18,11 +18,8 @@
 import java.util.Set;
 import java.util.concurrent.ConcurrentHashMap;
 
-
 import javax.jms.IllegalStateException;
-
 import javax.jms.Connection;
-
 import javax.jms.ConnectionConsumer;
 import javax.jms.ConnectionMetaData;
 import javax.jms.Destination;
@@ -93,7 +90,8 @@ public class SQSConnection implements Connection, QueueConnection {
 
     /**
      * Configures the amount of messages that can be prefetched by a consumer. A
-     * single consumer cannot prefetch more than 10 messages.
+     * single consumer cannot prefetch more than 10 messages in a single call to SQS,
+     * but it will make multiple calls as necessary.
      */
     private final int numberOfMessagesToPrefetch;
     private volatile boolean closed = false;

src/main/java/com/amazon/sqs/javamessaging/SQSMessageConsumerPrefetch.java

@@ -14,13 +14,15 @@
  */
 package com.amazon.sqs.javamessaging;
 
+import java.net.URI;
 import java.util.ArrayDeque;
 import java.util.ArrayList;
 import java.util.Iterator;
 import java.util.List;
 import java.util.Set;
 import java.util.UUID;
 
+import javax.jms.Destination;
 import javax.jms.JMSException;
 import javax.jms.MessageListener;
 
@@ -92,7 +94,14 @@ public class SQSMessageConsumerPrefetch implements Runnable, PrefetchManager {
      * Counter on how many messages are prefetched into internal messageQueue.
      */
     protected int messagesPrefetched = 0;
-
+    
+    /**
+     * Counter on how many messages have been explicitly requested.
+     * TODO: Consider renaming this class and several other variables now that
+     * this logic factors in message requests as well as prefetching.
+     */
+    protected int messagesRequested = 0;
+    
     /**
      * States of the prefetch thread
      */
@@ -163,9 +172,24 @@ protected void setMessageListener(MessageListener messageListener) {
             List<MessageManager> allPrefetchedMessages = new ArrayList<MessageManager>(messageQueue);
             sqsSessionRunnable.scheduleCallBacks(messageListener, allPrefetchedMessages);
             messageQueue.clear();
+
+            // This will request the first message if necessary.
+            // TODO: This may overfetch if setMessageListener is being called multiple
+            // times, as the session callback scheduler may already have entries for this consumer.
+            messageListenerReady();
         }
     }
 
+    /**
+     * Determine the number of messages we should attempt to fetch from SQS.
+     * Returns the difference between the number of messages needed (either for
+     * prefetching or by request) and the number currently fetched.
+     */
+    private int numberOfMessagesToFetch() {
+        int numberOfMessagesNeeded = Math.max(numberOfMessagesToPrefetch, messagesRequested);
+        return Math.max(numberOfMessagesNeeded - messagesPrefetched, 0);
+    }
+    
     /**
      * Runs until the message consumer is closed and in-progress SQS
      * <code>receiveMessage</code> call returns.
@@ -190,8 +214,7 @@ public void run() {
                 synchronized (stateLock) {
                     waitForStart();
                     waitForPrefetch();
-                    prefetchBatchSize = Math.min(
-                            (numberOfMessagesToPrefetch - messagesPrefetched), SQSMessagingClientConstants.MAX_BATCH);
+                    prefetchBatchSize = Math.min(numberOfMessagesToFetch(), SQSMessagingClientConstants.MAX_BATCH);
                 }
 
                 if (!isClosed()) {
@@ -290,7 +313,7 @@ protected void processReceivedMessages(List<Message> messages) {
 
     protected void waitForPrefetch() throws InterruptedException {
         synchronized (stateLock) {
-            while (messagesPrefetched >= numberOfMessagesToPrefetch && !isClosed()) {
+            while (numberOfMessagesToFetch() <= 0 && !isClosed()) {
                 try {
                     stateLock.wait();
                 } catch (InterruptedException e) {
@@ -332,7 +355,20 @@ protected javax.jms.Message convertToJMSMessage(Message message) throws JMSExcep
                 throw new JMSException("Not a supported JMS message type");
             }
         }
+        
         jmsMessage.setJMSDestination(sqsDestination);
+        
+        MessageAttributeValue replyToQueueNameAttribute = message.getMessageAttributes().get(
+                SQSMessage.JMS_SQS_REPLY_TO_QUEUE_NAME);
+        MessageAttributeValue replyToQueueUrlAttribute = message.getMessageAttributes().get(
+                SQSMessage.JMS_SQS_REPLY_TO_QUEUE_URL);
+        if (replyToQueueNameAttribute != null && replyToQueueUrlAttribute != null) {
+            String replyToQueueUrl = replyToQueueUrlAttribute.getStringValue();
+            String replyToQueueName = replyToQueueNameAttribute.getStringValue();
+            Destination replyToQueue = new SQSQueueDestination(replyToQueueName, replyToQueueUrl);
+            jmsMessage.setJMSReplyTo(replyToQueue);
+        }
+        
         return jmsMessage;
     }
 
@@ -366,12 +402,38 @@ protected void waitForStart() throws InterruptedException {
     public void messageDispatched() {
         synchronized (stateLock) {
             messagesPrefetched--;
-            if (messagesPrefetched < numberOfMessagesToPrefetch) {
+            messagesRequested--;
+            if (numberOfMessagesToFetch() > 0) {
                 notifyStateChange();
             }
         }
     }
 
+    @Override
+    public void messageListenerReady() {
+        synchronized (stateLock) {
+            // messagesRequested may still be more than zero if there were pending receive()
+            // calls when the message listener was set.
+            if (messagesRequested <= 0 && !isClosed() && messageListener != null) {
+                requestMessage();
+            }
+        }
+    }
+    
+    void requestMessage() {
+        synchronized (stateLock) {
+            messagesRequested++;
+            notifyStateChange();
+        }
+    }
+
+    private void unrequestMessage() {
+        synchronized (stateLock) {
+            messagesRequested--;
+            notifyStateChange();
+        }
+    }
+    
     public static class MessageManager {
 
         private final PrefetchManager prefetchManager;
@@ -405,28 +467,35 @@ javax.jms.Message receive(long timeout) throws JMSException {
             timeout = 0;
         }
 
-        MessageManager messageManager;
+        MessageManager messageManager = null;
         synchronized (stateLock) {
             // If message exists in queue poll.
             if (!messageQueue.isEmpty()) {
                 messageManager = messageQueue.pollFirst();
             } else {
-                long startTime = System.currentTimeMillis();
-
-                long waitTime = 0;
-                while (messageQueue.isEmpty() && !isClosed() &&
-                        (timeout == 0 || (waitTime = getWaitTime(timeout, startTime)) > 0)) {
-                    try {
-                        stateLock.wait(waitTime);
-                    } catch (InterruptedException e) {
-                        Thread.currentThread().interrupt();
+                requestMessage();
+            	try {
+                    long startTime = System.currentTimeMillis();
+    
+                    long waitTime = 0;
+                    while (messageQueue.isEmpty() && !isClosed() &&
+                            (timeout == 0 || (waitTime = getWaitTime(timeout, startTime)) > 0)) {
+                        try {
+                            stateLock.wait(waitTime);
+                        } catch (InterruptedException e) {
+                            Thread.currentThread().interrupt();
+                            return null;
+                        }
+                    }
+                    if (messageQueue.isEmpty() || isClosed()) {
                         return null;
                     }
-                }
-                if (messageQueue.isEmpty() || isClosed()) {
-                    return null;
-                }
-                messageManager = messageQueue.pollFirst();
+                    messageManager = messageQueue.pollFirst();
+            	} finally {
+            	    if (messageManager == null) {
+            	        unrequestMessage();
+            	    }
+            	}
             }
         }
         return messageHandler(messageManager);

src/main/java/com/amazon/sqs/javamessaging/SQSMessageProducer.java

@@ -34,13 +34,13 @@
 
 import com.amazon.sqs.javamessaging.message.SQSBytesMessage;
 import com.amazon.sqs.javamessaging.message.SQSMessage;
+import com.amazon.sqs.javamessaging.message.SQSMessage.JMSMessagePropertyValue;
 import com.amazon.sqs.javamessaging.message.SQSObjectMessage;
 import com.amazon.sqs.javamessaging.message.SQSTextMessage;
-import com.amazon.sqs.javamessaging.message.SQSMessage.JMSMessagePropertyValue;
-import com.amazonaws.util.Base64;
 import com.amazonaws.services.sqs.model.MessageAttributeValue;
 import com.amazonaws.services.sqs.model.SendMessageRequest;
 import com.amazonaws.services.sqs.model.SendMessageResult;
+import com.amazonaws.util.Base64;
 
 /**
  * A client uses a MessageProducer object to send messages to a queue
@@ -109,7 +109,15 @@ void sendInternal(SQSQueueDestination queue, Message rawMessage) throws JMSExcep
             throw new JMSException("Message body cannot be null or empty");
         }
         Map<String, MessageAttributeValue> messageAttributes = propertyToMessageAttribute((SQSMessage) message);
-        addMessageTypeReservedAttribute(messageAttributes, (SQSMessage) message, messageType);
+
+        /**
+         * These will override existing attributes if they exist. Everything that
+         * has prefix JMS_ is reserved for JMS Provider, but if the user sets that
+         * attribute, it will be overwritten.
+         */
+        addStringAttribute(messageAttributes, SQSMessage.JMS_SQS_MESSAGE_TYPE, messageType);
+        addReplyToQueueReservedAttributes(messageAttributes, message);
+
         SendMessageRequest sendMessageRequest = new SendMessageRequest(queue.getQueueUrl(), sqsMessageBody);
         sendMessageRequest.setMessageAttributes(messageAttributes);
 
@@ -218,19 +226,42 @@ Map<String, MessageAttributeValue> propertyToMessageAttribute(SQSMessage message
     private void addMessageTypeReservedAttribute(Map<String, MessageAttributeValue> messageAttributes,
                                                  SQSMessage message, String value) throws JMSException {
 
-        MessageAttributeValue messageAttributeValue = new MessageAttributeValue();
 
-        messageAttributeValue.setDataType(SQSMessagingClientConstants.STRING);
-        messageAttributeValue.setStringValue(value);
+        addStringAttribute(messageAttributes, SQSMessage.JMS_SQS_MESSAGE_TYPE, value);
+    }
 
-        /**
-         * This will override the existing attribute if exists. Everything that
-         * has prefix JMS_ is reserved for JMS Provider, but if the user sets that
-         * attribute, it will be overwritten.
-         */
-        messageAttributes.put(SQSMessage.JMS_SQS_MESSAGE_TYPE, messageAttributeValue);
+    /**
+     * Adds the reply-to queue name and url attributes during send as part of the send message
+     * request, if necessary
+     */
+    private void addReplyToQueueReservedAttributes(Map<String, MessageAttributeValue> messageAttributes,
+                                                   SQSMessage message) throws JMSException {
+
+        Destination replyTo = message.getJMSReplyTo();
+        if (replyTo instanceof SQSQueueDestination) {
+            SQSQueueDestination replyToQueue = (SQSQueueDestination)replyTo;
+    
+            /**
+             * This will override the existing attributes if exists. Everything that
+             * has prefix JMS_ is reserved for JMS Provider, but if the user sets that
+             * attribute, it will be overwritten.
+             */
+            addStringAttribute(messageAttributes, SQSMessage.JMS_SQS_REPLY_TO_QUEUE_NAME, replyToQueue.getQueueName());
+            addStringAttribute(messageAttributes, SQSMessage.JMS_SQS_REPLY_TO_QUEUE_URL, replyToQueue.getQueueUrl());
+        }
     }
 
+    /**
+     * Convenience method for adding a single string attribute.
+     */
+    private void addStringAttribute(Map<String, MessageAttributeValue> messageAttributes,
+                                    String key, String value) {
+        MessageAttributeValue messageAttributeValue = new MessageAttributeValue();
+        messageAttributeValue.setDataType(SQSMessagingClientConstants.STRING);
+        messageAttributeValue.setStringValue(value);
+        messageAttributes.put(key, messageAttributeValue);
+    }
+    
     /**
      * Sends a message to a queue.
      * <P>

src/main/java/com/amazon/sqs/javamessaging/SQSMessagingClientConstants.java

@@ -27,6 +27,8 @@ public class SQSMessagingClientConstants {
     public static final int MAX_BATCH = 10;
 
     public static final int MIN_BATCH = 1;
+    
+    public static final int MIN_PREFETCH = 0;
 
     /**
      * JMSMessage available user property types, which are mapped to message

src/main/java/com/amazon/sqs/javamessaging/SQSSessionCallbackScheduler.java

@@ -182,6 +182,10 @@ public void run() {
                         }
                     } finally {
                         session.finishedCallback();
+                        
+                        // Let the prefetch manager know we're available to
+                        // process another message (if there is a still a listener attached).
+                        messageManager.getPrefetchManager().messageListenerReady();
                     }
                 } catch (Throwable ex) {
                     LOG.error("Unexpected exception thrown during the run of the scheduled callback", ex);
@@ -211,7 +215,7 @@ void scheduleCallBacks(MessageListener messageListener, List<MessageManager> mes
             }
         }
     }
-            
+    
     void nackQueuedMessages() {
         synchronized (callbackQueue) {
             try {