As we have seen in the last examples, JAX-RS provides the ability to map exceptions to custom responses. This is a helpful functionality to implement transparent custom error handling without impacting the production code workflow.

A common issue when dealing with EJBs is that any thrown exception will be wrapped in an EJBException when accessed by any non-EJB context; for example, a request scoped JAX-RS resource. This makes exception handling quite cumbersome, as the EJBException would have to be unwrapped to inspect the cause.

By annotating custom exception types with @ApplicationException, the cause will not be wrapped:

import javax.ejb.ApplicationException;

@ApplicationException
public class GreetingException extends RuntimeException {

    public GreetingException(String message) {
        super(message);
    }
}

Calling an EJB that throws the GreetingException will not result in a wrapped EJBException and produce the exception type directly. The application can then define a JAX-RS exception mapper for the actual GreetingException type, similar to the one mapping constraint violations.

Specifying @ApplicationException(rollback = true) will furthermore cause the container to roll back an active transaction when the exception occurs.