Writing Custom Configuration Implementations for Mediators

You can write your own custom configurator for the Mediator implementation you write without relying on the Class Mediator or Spring extension for its initialization.

• The MediatorFactory implementation - Defines how to digest a custom XML configuration element to be used to create and configure the custom mediator instance.
• The MediatorSerializer implementation - Defines how a configuration should be serialized back into an XML configuration.

The custom MediatorFactory, MediatorSerializer implementations and the mediator class/es must be bundled as an OSGi bundle exporting these classes and placed into the ESB_HOME/repository/components/dropins folder, so that the Synapse runtime could find and load the definition.

A custom JAR file must bundle your classes implementing the Mediator interface, MediatorSerializer and the MediatorFactory interfaces. It should also contain two text files named org.apache.synapse.config.xml.MediatorFactory and org.apache.synapse.config.xml.MediatorSerializer which will contain the fully qualified name(s) of your MediatorFactory and MediatorSerializer implementation classes. Any dependencies should be made available through OSGi bundles in the same plugins directory.

The MediatorFactory interface listing, which you should implement, is given below and its getTagQName() method must define the fully qualified element of interest for custom configuration. The Synapse initialization will call back to this MediatorFactory instance through the createMediator(OMElement elem) method passing in this XML element, so that an instance of the mediator could be created utilizing the custom XML specification and returned.

The MediatorFactory Interface

package org.apache.synapse.config.xml;

import ...

/**
 * A mediator factory capable of creating an instance of a mediator through a given
 * XML should implement this interface
 */
public interface MediatorFactory {
    /**
     * Creates an instance of the mediator using the OMElement
     * @param elem
     * @return the created mediator
     */
    public Mediator createMediator(OMElement elem);

    /**
     * The QName of this mediator element in the XML config
     * @return QName of the mediator element
     */
    public QName getTagQName();
}

The MediatorSerializer Interface

package org.apache.synapse.config.xml;

import ...

/**
 * Interface which should be implemented by mediator serializers. Does the
 * reverse of the MediatorFactory
 */
public interface MediatorSerializer {

    /**
     * Return the XML representation of this mediator
     * @param m mediator to be serialized
     * @param parent the OMElement to which the serialization should be attached
     * @return the serialized mediator XML
     */
    public OMElement serializeMediator(OMElement parent, Mediator m);

    /**
     * Return the class name of the mediator which can be serialized
     * @return the class name
     */
    public String getMediatorClassName();
}