Jersey: Returning 400 error instead of 500 when given invalid request body

Question

I'm using Jersey's integrated Jackson processing to transform incoming JSON to a POJO, e.g.:

@POST @Consumes(MediaType.APPLICATION_JSON) public Response newCustomer( CustomerRepresentation customer) { ... } 

If a client sends JSON with invalid fields Jersey currently returns a 500 Internal Server Error. Instead, I'd like to return a 400 Bad Request, preferably with some meaningful detail indicating which fields are in error.

Any insight into how this could be accomplished? (At least returning a generic 400 instead of the completely inappropriate 500?)

Update: Here's the exception being generated server-side, before my handler is invoked:

javax.servlet.ServletException: org.codehaus.jackson.map.exc.UnrecognizedPropertyException:  Unrecognized field "this_isnt_a_known"_field" (Class com.redacted....), not marked as ignorable 

Answer 1

I was finally able to work around this problem by implementing an ExceptionMapper to catch the UnrecognizedPropertyException thrown by Jackson and map it to a 400 Bad Request response:

@Provider public class UnrecognizedPropertyExceptionMapper implements ExceptionMapper<UnrecognizedPropertyException> {      @Override     public Response toResponse(UnrecognizedPropertyException exception)     {         return Response                 .status(Response.Status.BAD_REQUEST)                 .entity( "'" + exception.getUnrecognizedPropertyName() + "' is an unrecognized field.")                 .type( MediaType.TEXT_PLAIN)                 .build();     }  } 

Answer 2

I tried mapping status 500 to status 400 with HolySamosa's answer but the exception was not caught by this mapper, and status 500 was still being returned.

After debugging I found that JsonParseException is being thrown and not UnrecognizedPropertyException. This is because I was sending some garbage text (that was not JSON at all).

When I sent a proper JSON from client side, with format that was not appropriate for my DTO on the server side, then I got UnrecognizedPropertyException. So there are two cases for this:

• when you send garbage that is not JSON and
• when you send JSON, but it is not a match for your DTO class.

Now I am returning status 400 for both.