Defining JMS proxy to listen to a particular queue in wso2esb

There are  use cases, where user needs to define number of jms queues for different purposes and proxies will listen to those queues and do further processing with messages.

There is a predefined service level parameter available in axis2   to make 'jms' proxies to listen particular queues.
Check the following simple sample(for qpid), where 'ErrorProxy" listens a  queue named as "errorqueue".

<proxy xmlns="http://ws.apache.org/ns/synapse" name="ErrorProxy" transports="https,http,jms" statistics="disable" trace="disable" startOnLoad="true">
   <target inSequence="ErrorInSequence" endpoint="ErrorQueueEndpoint" />
   <parameter name="transport.jms.ContentType">
      <rules>
         <jmsProperty>contentType</jmsProperty>
         <default>text/xml</default>
      </rules>
   </parameter>
   <parameter name="transport.jms.ConnectionFactory">myQueueConnectionFactory</parameter>
   <parameter name="transport.jms.DestinationType">queue</parameter>
   <parameter name="transport.jms.Destination">errorqueue</parameter>
</proxy> 

You have to enable jms transport in your axis2.xml.

eg:

<transportReceiver name="jms" class="org.apache.axis2.transport.jms.JMSListener">
  <parameter name="myQueueConnectionFactory" locked="false">
   <parameter name="java.naming.factory.initial" locked="false"> org.apache.qpid.jndi.PropertiesFileInitialContextFactory</parameter>
   <parameter name="java.naming.provider.url" locked="false">repository/conf /jndi.properties</parameter>
   <parameter name="transport.jms.ConnectionFactoryJNDIName" locked="false"> QueueConnectionFactory</parameter>
   <parameter name="transport.jms.ConnectionFactoryType" locked="false">queue< /parameter>
  </parameter>

Need to add following entry at jndi.properties file
  queue.errorqueue = example.errorqueue


ErrorInSequence Configuration
--------------------------------------

<sequence xmlns="http://ws.apache.org/ns/synapse" name="ErrorInSequence">
   <property name="FORCE_SC_ACCEPTED" value="true" scope="axis2" />
   <property name="OUT_ONLY" value="true" scope="default"/>
     <log level="custom">
      <property name="Picked message" value="************" />
   </log>
   <description></description>
</sequence> 

This sequence receives the error message,which is stored at error queue

Writing a custom class mediator in wso2esb

In this post we will look at how to write a very simple class mediator for wso2esb. All what you have to do is, just extend the AbstractMediator class (org.apache.synapse.mediators.AbstractMediator) or implement the Mediator interface (org.apache.synapse.Mediator). AbstractMediator contains the implementation for some methods , so it would be easy to use that class.
Say, in a scenario, when exception occurs  at ESB, we want to extract the error details , and need to do further processing. In the following  sample,  error details are extracted and printed as sysout..

package org.wso2.carbon.custommediator
import org.apache.synapse.MessageContext;
import org.apache.synapse.core.axis2.Axis2MessageContext;
import org.apache.synapse.mediators.AbstractMediator;

/**
* This custom mediator extracts error detail from synapse messagecontext.
* SynapseConfiguration would be;
*<insequence>
*   <class name="org.wso2.carbon.custommediator.CustomErrorDataMediator">
*   </class>
*</insequence>
**/

public class CustomErrorDataMediator extends AbstractMediator {

public boolean mediate(MessageContext synapseMsgContext) {
  String errorMesssage = (String) synapseMsgContext.getProperty("ERROR_MESSAGE");
  Exception exception = (Exception)  synapseMsgContext.              getProperty("ERROR_EXCEPTION");
  String errorCode = (String) synapseMsgContext.getProperty("ERROR_CODE");
  String errorDetail = (String) synapseMsgContext.getProperty("ERROR_DETAIL");

  System.out.println("Error Message is "+errorMesssage +"ErrorCode "+errorCode);

  return true;
 }
}

To build above code (*.jar as output), use following pom.xml file..

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">


    <modelVersion>4.0.0</modelVersion>
    <groupId> org.wso2.carbon.custommediator</groupId>
    <artifactId> org.wso2.carbon.custommediator</artifactId>
    <version>1.0</version>
    <packaging>jar</packaging>
 
    <dependencies>
        <dependency>
            <groupId>org.apache.synapse</groupId>
            <artifactId>synapse-core</artifactId>
            <version>1.4.0-wso2v2</version>       
        </dependency>      
    </dependencies>

    <build>
        <plugins>  
          <plugin>
                 <groupId>org.apache.maven.plugins</groupId>
                 <artifactId>maven-compiler-plugin</artifactId>
                 <version>2.0</version>
                 <configuration>
                     <source>1.5</source>
                     <target>1.5</target>
                 </configuration>
             </plugin>
        </plugins>
    </build>

</project>

Keep the *.jar in ESB/repository/component/lib folder and place the class mediator in your faultsequence.Whenever fault sequence get invoke, you will see the sysout at your server console.