How to use Class Mediator in WSO2 ESB

The Class Mediator creates an instance of a custom-specified class and sets it as a mediator. Use the Class mediator for user-specific, custom developments only when there is no built-in mediator that already provides the required functionality.

Creating a Class Mediator

There are two ways you can create a class mediator:

•     Implement the mediator interface
•     Extend AbstractMediator class

We can use WSO2 Developer Studio to Create class mediator easily.

Create a New Mediator Project By selecting File-> New Project -> WSO2 -> Extensions -> Project Types -> Mediator Project






It will create the class mediator by extending the AbstractMediator. Then we need to implement the mediate method which is invoked when the mediator is executed at the mediation flow.  The return statement of the mediate method decides whether the mediation flow should continue further or not.

MessageContext is the representation for a message within the ESB message flow. In the mediate method we get access to the message context. From the message context we can access message payload, message headers, properties, ESB configurations, etc. We can also set parameters to the mediator.

Sample Class mediator implementation is as follows.

package org.wso2.test;

import java.util.Enumeration;
import java.util.Map;
import java.util.Properties;

import org.apache.synapse.MessageContext; 
import org.apache.synapse.core.axis2.Axis2MessageContext;
import org.apache.synapse.mediators.AbstractMediator;

public class SampleClassMediator extends AbstractMediator { 

    public String classProperty;
    
    public boolean mediate(MessageContext context) { 
        //Mediator Property
        System.out.println("------Mediator Property-------");
        System.out.println("Using Property :  " + classProperty);
        
        //Accessing Message Properties
        System.out.println("------Message Properties-------");
        String prop = (String) context.getProperty("StringProp");
        System.out.println("Using msg Prop : "+ prop);
        
        //Accessing Axis2 Properties
        System.out.println("------Axis2 Properties-------");
        Map<String,Object> mapAxis2Properties = ((Axis2MessageContext)context).getAxis2MessageContext().getProperties();
        for (Map.Entry entry : mapAxis2Properties.entrySet()) {
            System.out.println("AXIS:"+entry.getKey() + ", " + entry.getValue());
        }
        
        //Accessing Transport Headers
        System.out.println("------Transport Headers-------");
        Map<String,Object> mapTransportProperties = (Map<String, Object>) ((Axis2MessageContext)context).getAxis2MessageContext().getProperty("TRANSPORT_HEADERS");
        for (Map.Entry entry : mapTransportProperties.entrySet()) {
            System.out.println("TRANS:" +entry.getKey() + ", " + entry.getValue());
        }
        
        //Accessing Syanpse Configuration properties
        System.out.println("------Synapse Config Properties-------");
        Properties p = ((Axis2MessageContext)context).getEnvironment().getSynapseConfiguration().getProperties();
        Enumeration keys = p.keys();
        while(keys.hasMoreElements()){
            String key = (String)keys.nextElement();
            String value = (String)p.get(key);
            System.out.println("PRP: "+ key + " | " + value);
        }
        
        //Accessing Soap envelop
        System.out.println("------Soap envelop-------");
        System.out.println("MSG : " + context.getEnvelope());
        return true; 
    }
    
    public String getClassProperty() {
        return classProperty;
    }
    
    public void setClassProperty(String propValue) {
        this.classProperty = propValue;
    }
}

After implementing the method export the project as .jar file and copy to /repository/components/lib folder and restart the ESB.

Creating the Proxy service

You can use the implemented class mediator within a proxy service as follows.

<?xml version="1.0" encoding="UTF-8"?>
<proxy xmlns="http://ws.apache.org/ns/synapse"
       name="TestClassMedProxy"
       transports="http,https"
       statistics="disable"
       trace="disable"
       startOnLoad="true">
   <target>
      <inSequence>
         <log level="custom">
            <property name="BEGIN" value="Begin Sequence"/>
         </log>
         <property name="StringProp"
                   value="&#34;TestString&#34;"
                   scope="default"
                   type="STRING"/>
         <class name="org.wso2.test.SampleClassMediator">
            <property name="classProperty" value="5"/>
         </class>
      </inSequence>
      <outSequence>
         <send/>
      </outSequence>
   </target>
   <description/>
</proxy>
                                

Then send a request to the proxy service and you will see following output in the consloe as we are printing to the console.

[2016-10-18 07:03:27,414]  INFO - LogMediator BEGIN = Begin Sequence
------Mediator Property-------
Using Property :  5
------Message Properties-------
Using msg Prop : "TestString"
------Axis2 Properties-------
AXIS:addressing.validateAction, false
AXIS:local_WSO2_WSAS, org.wso2.carbon.core.init.CarbonServerManager@182ab504
AXIS:CARBON_TASK_JOB_METADATA_SERVICE, org.wso2.carbon.task.JobMetaDataProviderServiceHandler@4d72eb52
AXIS:file.resource.map, {}
AXIS:CARBON_TASK_MANAGEMENT_SERVICE, org.wso2.carbon.task.TaskManagementServiceHandler@fdccc49
AXIS:mediation.event.broker, org.wso2.carbon.event.core.internal.CarbonEventBroker@51c8cdb1
AXIS:CARBON_TASK_MANAGER, org.wso2.carbon.task.TaskManager@1c87c019
AXIS:wso2tracer.msg.seq.buff, org.wso2.carbon.utils.logging.CircularBuffer@467590a0
AXIS:ContainerManaged, true
AXIS:WORK_DIR, /home/anupama/Anupama/Workspace/WSO2Products/ESB/wso2esb-4.9.0/tmp/work
AXIS:PASS_THROUGH_TRANSPORT_WORKER_POOL, org.apache.axis2.transport.base.threads.NativeWorkerPool@2fa2b2a3
AXIS:CARBON_TASK_REPOSITORY, org.apache.synapse.task.TaskDescriptionRepository@389047a3
AXIS:local_current.server.status, RUNNING
AXIS:tenant.config.contexts, {}
AXIS:CONFIGURATION_MANAGER, org.wso2.carbon.mediation.initializer.configurations.ConfigurationManager@1a35cfa0
AXIS:service.epr.map, {}
AXIS:primaryBundleContext, org.eclipse.osgi.framework.internal.core.BundleContextImpl@2506f4
AXIS:GETRequestProcessorMap, {info=org.wso2.carbon.core.transports.util.InfoProcessor@70afacd6, wsdl=org.wso2.carbon.core.transports.util.Wsdl11Processor@4a223fca, wsdl2=org.wso2.carbon.core.transports.util.Wsdl20Processor@7035d472, xsd=org.wso2.carbon.core.transports.util.XsdProcessor@44c95d1b, tryit=org.wso2.carbon.tryit.TryitRequestProcessor@490d9048, wadltryit=org.wso2.carbon.tryit.WADLTryItRequestProcessor@120a3acc, stub=org.wso2.carbon.wsdl2form.StubRequestProcessor@4c42eabb, wsdl2form=org.wso2.carbon.wsdl2form.WSDL2FormRequestProcessor@42ed57ad, wadl2form=org.wso2.carbon.tryit.WADL2FormRequestProcessor@67c70068}
------Transport Headers-------
TRANS:Content-Type, application/soap+xml; charset=UTF-8; action="urn:mediate"
TRANS:Cookie, menuPanel=visible; menuPanelType=main; region1_manage_menu=visible; JSESSIONID=4B3870641F979576800AB05FAEB9360D; requestedURI=../../carbon/admin/index.jsp; region1_configure_menu=none; region3_registry_menu=none; region4_monitor_menu=none; region5_tools_menu=none; current-breadcrumb=manage_menu%2Cservices_menu%2Cservices_list_menu%23
TRANS:Host, anupama:8280
TRANS:Transfer-Encoding, chunked
TRANS:User-Agent, Axis2
------Synapse Config Properties-------
PRP: synapse.xpath.func.extensions | org.wso2.carbon.mediation.security.vault.xpath.SecureVaultLookupXPathFunctionProvider
PRP: statistics.clean.interval | 1000
PRP: synapse.commons.json.preserve.namespace | false
PRP: resolve.root | ./.
PRP: synapse.home | .
PRP: __separateRegDef | true
PRP: synapse.global_timeout_interval | 120000
PRP: synapse.temp_data.chunk.size | 3072
PRP: statistics.clean.enable | true
PRP: synapse.observers | org.wso2.carbon.mediation.dependency.mgt.DependencyTracker
PRP: synapse.sal.endpoints.sesssion.timeout.default | 600000
PRP: synapse.carbon.ext.tenant.info | org.wso2.carbon.mediation.initializer.handler.CarbonTenantInfoConfigurator
------Soap envelop-------
MSG : <?xml version='1.0' encoding='utf-8'?><soapenv:Envelope xmlns:soapenv="http://www.w3.org/2003/05/soap-envelope"><soapenv:Body><test>Test Data</test></soapenv:Body></soapenv:Envelope>