Question

I have the following code:

@POST
@Path("query")
@Produces(MediaType.APPLICATION_JSON)
public MyObject myMethod(@FormParam("id") String id)
{
    //if some condition is met
    if(...)
      throw new WebApplicationException(Response.Status.SERVICE_UNAVAILABLE);
    else
      //proceed to my logic and return myObject
}

So basically, if my web client, using AJAX, receives a Response.Status.SERVICE_UNAVAILABLE, it will show a customized web page. If the call is successful, it will show a different web page.

My questions is: Is there anyway that in myMethod, I can return the Response.Status.SERVICE_UNAVAILABLE without throwing the exception. Something like:

if(...)
   return Response.Status.SERVICE_UNAVAILABLE)
else
   //proceed my logic and return myObject  

I basically want the client to know that its request cannot be fulfilled at this time and show a customized web page.

Answer 1

Your method should return a Response, instead of MyObject:

@POST
@Path("query")
@Produces(MediaType.APPLICATION_JSON)
public Response myMethod(@FormParam("id") String id) {
  if (/* error */) {
    return Response.status(Response.Status.SERVICE_UNAVAILABLE).build();
  }
  return Response.ok().entity(new MyObject(/* ... */)).build();
}

However, I would strongly recommend to use WebApplicationException for such situations, mostly for the sake of logical separation of regular and exceptional cases. This SERVICE_UNAVAILABLE response status (HTTP code 503) is a clear indicator of error, not a normal execution flow.