guide exception handling

Table of Contents

• Exception Handling in Quarkus
  • Exception mapping

Exception Handling in Quarkus

For handling exceptions within a Spring application, devon4j provides the devon4j-rest module, which provides a RestServiceExceptionFacade to handle all exceptions in a consistent way. Since the module is not suitable for Quarkus, we need to implement this ourselves.

This guide shows how to do just that. For an example, see our Quarkus reference application.

Exception mapping

We suggest to implement the exception handling the JAX-RS way using ExceptionMapper<T>.

RESTEasy provides several exception mappers out of the box. For example, RESTEasy’s NotFoundExceptionMapper provides a web page that shows all available endpoints in dev mode.

Even though this looks really nice, we want to have consistent exception handling throughout the application. We create an abstract class AbstractExceptionMapper that acts as a base class for all of the more specific exception mappers and where the response is created in a consistent manner. You can find an example of this class here.

AbstractExceptionMapper

public abstract class AbstractExceptionMapper {

  ...

  protected Response createResponse(int status, String errorCode, Exception exception) {

    Map<String, Object> jsonMap = new HashMap<>();
    jsonMap.put("code", errorCode);
    if (this.exposeInternalErrorDetails) {
      jsonMap.put("message", getExposedErrorDetails(exception));
    } else {
      jsonMap.put("message", exception.getMessage());
    }
    jsonMap.put("uri", this.uriInfo.getPath());
    jsonMap.put("uuid", UUID.randomUUID());
    jsonMap.put("timestamp", ZonedDateTime.now().toString());
    return Response.status(status).type(MediaType.APPLICATION_JSON).entity(jsonMap).build();
  }

  ...
}

For the exceptions that may occur during runtime, we create an ExceptionMapper that extends from our AbstractExceptionMapper class. To make the class discoverable by the JAX-RS runtime, we have to annotate the class with @Provider.

NotFoundExceptionMapper

@Provider
public class NotFoundExceptionMapper extends AbstractExceptionMapper implements ExceptionMapper<NotFoundException> {

  @Override
  public Response toResponse(NotFoundException exception) {

    ...

    return createResponse(Status.NOT_FOUND.getStatusCode(), exception.getClass().getSimpleName(), exception);
  }
}

Note	Unlike the RestServiceExceptionFacade of the devon4j-rest module, we cannot use ExceptionMapper<Throwable> in Quarkus, because in this case, the exception mapper of RESTEasy would be used, since they are more specific.