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Class Mediator

The Class Mediator creates an instance of a custom-specified class and sets it as a mediator. The class must implement the org.apache.synapse.api.Mediator interface. If any properties are specified, the corresponding setter methods are invoked once on the class during initialization.

The Class mediator is a custom Java class, which you need to maintain by yourself. Therefore, it is recommended to use the Class mediator only for not frequently re-used custom developments and very user-specific scenarios, for which, there is no built-in mediator that already provides the required functionality.

Your class mediator might not be picked up and updated if you use an existing package when creating. For best results, use WSO2 Integration Studio for debugging Class mediators.

Syntax

<class name="class-name">
   <property name="string" (value="literal" | expression="[XPath|json-eval(JSON Path)]")/>*
</class>

Configuration

Class Name: The name of the class. To load a class, enter the qualified name of the relevant class in this parameter and click Load Class.

Example

In this configuration, the Micro Integrator sends the requested message to the endpoint specified via the Send mediator. This endpoint is the Axis2server running on port 9000. The response message is passed through a Class mediator before it is sent back to the client. Two parameters named variable1 and variable2 are passed to the instance mediator implementation class ( SimpleClassMediator).

Info

If you want, you can pass the same variables as a value or an expression:

  • Example for passing the variable as a value: <property name="variable1" value="10"/>

  • Example for passing the variable as an expression: <property name="variable2" expression="get-property('variable1')"/>
    For more information on using the get property method, see the Property Mediator.

Warning

Using the class variables with expressions will lead to the values evaluated being mixed up when there are concurrent requests and will lead to erroneous behaviors. 

<sequence xmlns="http://ws.apache.org/ns/synapse" name="errorHandler">
    <makefault>
        <code value="tns:Receiver" xmlns:tns="http://www.w3.org/2003/05/soap-envelope"/>
        <reason value="Mediation failed."/>
    </makefault>
    <send/>
</sequence>

<proxy name="SimpleProxy" transports="http https" startonload="true" trace="disable" xmlns="http://ws.apache.org/ns/synapse">
    <target>
         <inSequence>
                <send>
                    <endpoint name="stockquote">
                        <address uri="http://localhost:9000/services/SimpleStockQuoteService"/>
                    </endpoint>
                </send>
            </inSequence>
            <outSequence>
                <class name="samples.mediators.SimpleClassMediator">
                    <property name="variable1" value="10"/>
                    <property name="variable2" value="5"/>
                </class>
                <send/>
            </outSequence>
            <faultSequence>
                 <sequence key="errorHandler"/>
            </faultSequence>
    </target>
</proxy>

See the following sample Class Mediator and note the SynapseMessageContext and the full Synapse API in there.

package samples.mediators;

    import org.apache.synapse.MessageContext;
    import org.apache.synapse.mediators.AbstractMediator;
    import org.apache.axiom.om.OMElement;
    import org.apache.axiom.om.OMAbstractFactory;
    import org.apache.axiom.om.OMFactory;
    import org.apache.axiom.soap.SOAPFactory;
    import org.apache.commons.logging.Log;
    import org.apache.commons.logging.LogFactory;

    import javax.xml.namespace.QName;

    public class SimpleClassMediator extends AbstractMediator {

        private static final Log log = LogFactory.getLog(SimpleClassMediator.class);

        private String variable1="10";

        private String variable2="10";

        private int variable3=0;

        public SimpleClassMediator(){}

        public boolean mediate(MessageContext mc) {
            // Do somthing useful..
            // Note the access to the Synapse Message context
            return true;
        }

        public String getType() {
            return null;
        }

        public void setTraceState(int traceState) {
            traceState = 0;
        }

        public int getTraceState() {
            return 0;
        }

        public void setVariable1(String newValue) {
            variable1=newValue;
        }

        public String getVariable1() {
            return variable1;
        }

        public void setVariable2(String newValue){
            variable2=newValue;
        }

        public String getVariable2(){
            return variable2;
        }
    }