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<h1>Asynchronous Send Acknowledgements Example</h1>
<p>Asynchronous Send Acknowledgements are an advanced feature of ActiveMQ which allow you to
receive acknowledgements that messages were successfully received at the server in a separate thread to the sending thread<p/>
<p>In this example we create a normal JMS session, then set a SendAcknowledgementHandler on the JMS
session's underlying core session. We send many messages to the server without blocking and asynchronously
receive send acknowledgements via the SendAcknowledgementHandler.
<p>For more information on Asynchronous Send Acknowledgements please see the user manual</p>
<h2>Example step-by-step</h2>
<p><i>To run the example, simply type <code>mvn verify</code> from this directory</i></p>
<ol>
<li>First we need to get an initial context so we can look-up the JMS connection factory and destination objects from JNDI. This initial context will get it's properties from the <code>client-jndi.properties</code> file in the directory <code>../common/config</code></li>
<pre class="prettyprint">
<code>InitialContext initialContext = getContext();</code>
</pre>
<li>We look-up the JMS queue object from JNDI</li>
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<code>Queue queue = (Queue) initialContext.lookup("/queue/exampleQueue");</code>
</pre>
<li>We look-up the JMS connection factory object from JNDI</li>
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<code>ConnectionFactory cf = (ConnectionFactory) initialContext.lookup("/ConnectionFactory");</code>
</pre>
<li>We create a JMS connection</li>
<pre class="prettyprint">
<code>connection = cf.createConnection();</code>
</pre>
<li>Define a SendAcknowledgementHandler which will receive asynchronous acknowledgements</li>
<pre class="prettyprint">
<code>
class MySendAcknowledgementsHandler implements SendAcknowledgementHandler
{
int count = 0;
public void sendAcknowledged(final Message message)
{
System.out.println("Received send acknowledgement for message " + count++);
}
}
</code>
</pre>
<li>Create a JMS session</li>
<pre class="prettyprint">
<code>Session session = connection.createSession(false, Session.AUTO_ACKNOWLEDGE);</code>
</pre>
<li>Set the handler on the underlying core session</li>
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<code>
ClientSession coreSession = ((ActiveMQSession)session).getCoreSession();
coreSession.setSendAcknowledgementHandler(new MySendAcknowledgementsHandler());
</code>
</pre>
<li>Create a JMS Message Producer</li>
<pre class="prettyprint">
<code>
MessageProducer producer = session.createProducer(queue);
producer.setDeliveryMode(DeliveryMode.NON_PERSISTENT);
</code>
</pre>
<li>Send 5000 messages, the handler will get called asynchronously some time later after the messages are sent.</li>
<pre class="prettyprint">
<code>
final int numMessages = 5000;
for (int i = 0; i < numMessages; i++)
{
javax.jms.Message jmsMessage = session.createMessage();
producer.send(jmsMessage);
System.out.println("Sent message " + i);
}
</code>
</pre>
<li>And finally, <b>always</b> remember to close your JMS connections and resources after use, in a <code>finally</code> block. Closing a JMS connection will automatically close all of its sessions, consumers, producer and browser objects</li>
<pre class="prettyprint">
<code>finally
{
if (initialContext != null)
{
initialContext.close();
}
if (connection != null)
{
connection.close();
}
}</code>
</pre>
</ol>
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