TopLink performs all type conversions through the use of a ConversionManager class ( oracle.toplink.internal.helper). This class can be extended to perform any additional conversions or to customize existing conversions. The source code to the ConversionManager is shipped with the product in the source.jar library.

For the purpose of this example a subclass of ConversionManager is created called MyConversionManager. This new class must support converting from a String into an Answer instance and from an Answer instance into a String.

The important methods to overwrite are:

public Object convertObject(Object source, Class javaClass)
public String convertObjectToString(Object source)

For this particular case an additional method was added for converting into an Answer:

public Answer convertObjectToAnswer(Object source)

The source for MyConversionManager.java.
 

The new conversion manager must be installed into the runtime using the following code:

MyConversionManager cm = new MyConversionManager();
ConversionManager.setDefaultManager(cm);
event.getSession().getLogin().getPlatform().setConversionManager(cm);

The easiest way to install the conversion manager is to use a SessionEventListener . This listener will implement the preLogin event and register the new conversion manager as per the above code.

The source for ConversionManagerSetup.java.
 

The ConversionManagerSetup is configured for use by the TopLink runtime through the sessions.xml configuration file. The following line added to a session’s definition will cause the event listener to be registered and invoked. This assumes the use of SessionManager.

<event-listener-class>
oracle.toplink.example.conversion.ConversionManagerSetup
</event-listener-class>

The source for sessions.xml.