Chapter 24. Exception Handling
24.1. Exception Mappers
ExceptionMappers are custom, application-provided components that can catch application exceptions and write specific HTTP responses. They are associated with @Provider, and implement the following interface:
package javax.ws.rs.ext;
import javax.ws.rs.core.Response;
/**
* Contract for a provider that maps Java exceptions to
* {@link javax.ws.rs.core.Response}. An implementation of this interface must
* be annotated with {@link Provider}.
*
* @see Provider
* @see javax.ws.rs.core.Response
*/
public interface ExceptionMapper<E>
{
/**
* Map an exception to a {@link javax.ws.rs.core.Response}.
*
* @param exception the exception to map to a response
* @return a response mapped from the supplied exception
*/
Response toResponse(E exception);
}
When an application throws an exception, the exception is caught by the JAX-RS runtime. JAX-RS then scans registered
ExceptionMappers to locate one which supports marshalling the exception type thrown. An example ExceptionMapper follows:
@Provider
public class EJBExceptionMapper implements ExceptionMapper<javax.ejb.EJBException>
{
Response toResponse(EJBException exception) {
return Response.status(500).build();
}
}
ExceptionMappers are registered in the same way as MessageBodyReaders and MessageBodyWriters: by scanning through the RESTEasy provider context-param (if you are deploying in a WAR file), or programmatically through the ResteasyProviderFactory class.
