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Generally, JMS is used for one-way, asynchronous message exchange. However you can perform synchronous messaging also with JMS. Described below is how to configure WSO2 ESB for two-way and quad-channel synchronous messaging.
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Diagram 4 : Dual-channel JMS synchronous invocations
The following example code shows configuration of WSO2 ESB for dual-channel JMS synchronous invocations.
| Code Block | ||||
|---|---|---|---|---|
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<proxy name="StockQuoteProxy" transports="http">
<target>
<endpoint>
<address uri="jms:/SimpleStockQuoteService?transport.jms.ConnectionFactoryJNDIName=QueueConnectionFactory& java.naming.factory.initial=org.apache.activemq.jndi.ActiveMQInitialContextFactory&java.naming.provider.url=tcp://localhost:61616&transport.jms.DestinationType=queue&transport.jms.ReplyDestination=SimpleStockQuoteServiceReply"/>
</endpoint>
<inSequence>
<property action="set" name="transport.jms.ContentTypeProperty" value="Content-Type" scope="axis2"/>
</inSequence>
<outSequence>
<property action="remove" name="TRANSPORT_HEADERS" scope="axis2"/>
<send/>
</outSequence>
<target>
<publishWSDL uri="file:repository/conf/sample/resources/proxy/sample_proxy_1.wsdl"/>
</proxy> |
The message flow of the sample code is as follows:
- The ESB proxy service accepts messages via HTTP and places them in SimpleStockQuoteService JMS queue.
- The back-end consumes these messages from the queue and places response messages in the SimpleStockQuoteServiceReply queue.
- When a reply is available in the SimpleStockQuoteServiceReply queue, the ESB proxy will pick the response message and send it as the response to the client via HTTP connection.
To send a HTTP message to the ESB proxy service, execute following command from <ESB_HOME>/sample/axis2Client directory.
| Code Block |
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ant stockquote -Daddurl=http://localhost:8280/services/StockQuoteProxy -Dmode=placeorder -Dsymbol=MSFT |
To co-relate request and response JMS messages, the ESB uses a JMS correlation ID internally. For more information, refer to http://www.eaipatterns.com/RequestReplyJmsExample.html.
Since this is a two-way invocation, the inSequence does not have the configuration <property action="set" name="OUT_ONLY" value="true"/>.
The response queue name is defined using transport.jms.ReplyDestination parameter in the JMS connection URL.
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Diagram 5 : Quad-channel JMS synchronous invocations
The following example code shows configuration of WSO2 ESB for quad-channel JMS synchronous invocations.
| Code Block | ||||
|---|---|---|---|---|
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<proxy name="QuadJMS" transports="jms">
<target>
<inSequence>
<property action="set" name="transport.jms.ContentTypeProperty" value="Content-Type" scope="axis2"/>
<send>
<endpoint>
<address uri="jms:/BEReq?transport.jms.ConnectionFactoryJNDIName=QueueConnectionFactory& java.naming.factory.initial=org.apache.activemq.jndi.ActiveMQInitialContextFactory&java.naming.provider.url=tcp://localhost:61616&transport.jms.DestinationType=queue&transport.jms.ReplyDestination=BERes"/>
</endpoint>
</send>
</inSequence>
<outSequence>
<send/>
</outSequence>
<target>
<parameter name="transport.jms.Destination">ClientReq</parameter>
</proxy> |
The message flow of the sample code is as follows:
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