This document discusses using Java Messaging Service (JMS) for synchronous communication between a client and server with Mule ESB. It provides an example using Mule ESB and ActiveMQ to demonstrate a JMS back-channel, where a client sends a message that is received and a response returned. The response is sent to the client via a temporary queue created for each message exchange.

2.  Java Messaging Service is often used for
asynchronous communication between client and
server. Mule ESB allows JMS for synchronous
communication wherein the client and server can
be be completely decoupled . The JMS
synchronous communication is also referred to
as “JMS Back-channel”. The JMS back-channel is
usually not provided by the JMS protocol or any
JMS brokers and has to be implemented by the
applications. In this blog, a simple use case of
the synchronous JMS communication using Mule
ESB and Active MQ is described.

3.  In the below example, a string message is sent
and received in order to demonstrate JMS back-
channel. The Active MQ is used as a message
broker for the demo. The JMS back-channel can
be implemented by Mule ESB in two ways which
are described in the following sections.
 <jms:activemq-connector name="Active_MQ"
username="username" password="password"
brokerURL="tcp://localhost:63636"
validateConnections="true" doc:name="Active
MQ" />

5.  Client Flow

6.  <flow name="jmsmessagepublisher"
doc:name="jmsmessagepublisher"><http:inbound-
endpoint exchange-pattern="request-response"
host="localhost" port="1111" path="backchannel"
doc:name="HTTP" /><set-payload value="Hello
World from Sender" doc:name="Set Payload"
/><response><logger message="Final Response:
#[payload]" level="INFO" doc:name="Logger"
/></response><logger message="Sending Message:
#[payload]" level="INFO" doc:name="Logger"
/><jms:outbound-endpoint exchange-
pattern="request-response" queue="myQueue"
connector-ref="Active_MQ" doc:name="JMS"
/></flow>

8.  <flow name="jmsmessagereceiver"
doc:name="jmsmessagereceiver"><jms:inbound
-endpoint queue="myQueue" connector-
ref="Active_MQ" doc:name="JMS" exchange-
pattern="request-response"/><logger
message="Received Message: #[payload]"
level="INFO" doc:name="Logger"/><set-payload
value="Hello World from Receiver"
doc:name="Set Payload"/><logger
message="New Message Back to Sender:
#[payload]" level="INFO"
doc:name="Logger"/></flow>

9.  A temporary response queue for JMS backchannel
is created internally using Request-response JMS
endpoints.
 Response is sent to the client via a temporary
queue.
 The response queue is anonymous and Mule
automatically sets the JMS_REPLY_TO property.
This property instructs Mule on where the reply
message needs to be sent.
 The response queue is created for every message
exchange and is destroyed immediately after the
client receives the response.
 JMSCorrelationId ensures proper sequencing.

11.  Open a browser and type the below URL
 http://localhost:1111/backchannel
 This will invoke the “jmsmessagepublisher” flow
and will send a message to request queue.
 “Jmsmessagereceiver” queue will log the request
message received and return a new message.
 “Jmsmessagepublisher” flow will receive the
message returned from the “Jmsmessagereceiver”
queue and will log the final response.
 The final response will be printed on the browser.
 If using approach 1 and running in INFO mode,
the temporary queue and correlation id are saved
in logs.