How to catch the original Exception, when using WebServices? - json

Question

After searching for days now and reading pretty much everything related to that, I'm finally posting my question here, since I couldn't find a solution for my specific problem.
I want my REST WebServices to return the original Exception, that has been thrown or at least the correct StackTrace. To test this, I'm using JUnit integrationtests and Wildfly 13 as app-server. After researching I found 2 possible solutions.
1.Using Exception Mappers
While this magical thing catches all of my Exceptions and allows me to return a Response, I've noticed that my StackTrace is changed if I use it like in the example. For example, "com.test.TestClass" is turned into "null.thread" or "null.interceptor". It seems like somehow the exception is changed on the way and the paths to the class are lost or censored, but I can't make sense of it.
Also I couldn't find any restrictions for the Response.entity, be it size, datatype or security.
As far as I understand, you can catch the ExceptionMapper Response OR a WebApplicationException, which contains the response. In my case, the response in the WebApplicationException contains all the relevant data except the (correct) StackTrace.
2.Using WebApplicationException
Another Solution would be to simply throw WebApplicationException instead of ECEException and not using a mapper. If I do that and catch it, the Exception is empty though. It doesn't contain any of the data set, it's always 500 - InternalServerError (I guess, Wildfly couldn't handle it then and threw an exception itself).
Or is it not supposed to be catched/thrown like that? Do I need to convert it to JSon or can I expect it to simply work out of the box with my annotations in the WebServiceInterface and the Response MediaType? Does it even make sense to put a full Response within a WebApplicationException? I mean, both contain fields for the ErrorCode, which seems redundand, even though there is a constructor for that approach.
Long story short:
What's the best approach to catch all possible exceptions and retrieve the full stack trace? Reading this post, I guess catching all "Exception"s is fine and they are always returned as WebApplicationExceptions, but the stack trace is still gone/malformed... your thoughts?
**JUnitTest**
#Test
public void testCreateTask_ClusterInvalid() throws IOException {
final RPETask taskToCreate = new RPETask();;
try
{
final long tid = taskManagerWebService.createTask(taskToCreate);
}
catch (WebApplicationException e) //Responses are ALWAYS catched as WebApplicationException
{
Response response = e.getResponse();
String emString = response.readEntity(String.class);
Gson gson = new Gson();
ECEWebErrorMessage errorMessage = gson.fromJson(emString, ECEWebErrorMessage.class);
errorMessage.displayErrorInformationOnConsole();
}
}
**WebServiceInterface**
#POST
#Path(URI_CREATE_TASK)
#Consumes(WebServiceNames.JSON)
#Produces(WebServiceNames.JSON)
long createTask(final RPETask task) throws ECEException;
**WebService**
#Override
public long createTask(final RPETask task) throws ECEException {
if (LOGGER.isTraceEnabled()) {
LOGGER.trace("createTask(" + task + ")");
}
return taskManager.createTask(task);
}
**ManagerBeanInterface**
long createTask(RPETask task) throws ECEException;
**ManagerBean**
#Override
public long createTask(final RPETask task) throws ECEException {
final ClusterEngineBean cluster = find(ClusterEngineBean.class, task.getCluster());
if (cluster == null) {
throw new ECEObjectNotFoundException(ClusterEngineBean.class, task.getCluster());
}
}
**ExceptionMapper**
#Provider
public class GenericWebExceptionMapper implements ExceptionMapper<Exception> {
final Log logger = LogFactory.getLog(getClass());
#Override
public Response toResponse(Exception ex) {
//At this point, the Exception is fully available -> Sending it as Response breaks it!
logger.error("GenericWebExceptionMapper -> toResponse(Throwable ex)", ex);
ECEWebErrorMessage errorMessage = new ECEWebErrorMessage(500,
ex.getMessage(),
ex.getClass().getCanonicalName(),
ex.getStackTrace());
return Response.status(Status.INTERNAL_SERVER_ERROR)
.entity(errorMessage)
.type(MediaType.APPLICATION_JSON)
.build();
}
}

Answer 1

After more research I've finally found a solution for myself.
Why is the StackTrace gone/malformed?
It's for security reasons. Wildfly automatically detects outgoing StackTraces and censors them, using interceptors. Im not sure if you can do anything about that, but I guess you shouldn't do that anyway.
What is the best approach?
Using Exception Mappers worked for me. Instead of catching them as WebApplicationException, you can always expect a response with the appropriote error code and handle them that way. For example error code 200 = OK, do this... error code 404 = NOTFOUND, do that...I that case your WebServices should always return Responses and contain the object you want to retreive in the entity field of the Response.
Feel free to add additional information to this solution.