How I return HTTP 404 JSON/XML response in JAX-RS

问题:

I have the following code:

@Path("/users/{id}")
public class UserResource {

    @Autowired
    private UserDao userDao;

    @GET
    @Produces({MediaType.APPLICATION_XML, MediaType.APPLICATION_JSON})
    public User getUser(@PathParam("id") int id) {
        User user = userDao.getUserById(id);
        if (user == null) {
            throw new NotFoundException();
        }
        return user;
    }

If I request for a user that doesn't exists, like /users/1234, with "Accept: application/json", this code returns an HTTP 404 response like one would expect, but returns Content-Type sets to text/html and a body message of html. Annotation @Produces is ignored.

Is it a problem of code or a problem of configuration?

回答1:

Your @Produces annotation is ignored because uncaught exceptions are processed by the jax-rs runtime using a predefined (default) ExceptionMapper If you want to customize the returned message in case of a specific exception you can create your own ExceptionMapper to handle it. In your case you need one to handle the NotFoundException exception and query the "accept" header for the requested type of the response:

@Provider
public class NotFoundExceptionHandler implements ExceptionMapper<NotFoundException>{

    @Context
    private HttpHeaders headers;

    public Response toResponse(NotFoundException ex){
        return Response.status(404).entity(yourMessage).type( getAcceptType()).build();
    }

    private String getAcceptType(){
         List<MediaType> accepts = headers.getAcceptableMediaTypes();
         if (accepts!=null && accepts.size() > 0) {
             //choose one
         }else {
             //return a default one like Application/json
         }
    }
}

回答2:

You can use the Response return. Example below:

@GET
@Path("{id}")
@Produces(MediaType.APPLICATION_JSON)
public Response get(@PathParam("id") Long id) {
    ExampleEntity exampleEntity = getExampleEntityById(id);

    if (exampleEntity != null) {
        return Response.ok(exampleEntity).build();
    }

    return Response.status(Status.NOT_FOUND).build();
}

回答3:

that 404 is returned by your server as it is expected that you will pass things in following form

/users/{id}

but you are passing it as

/users/user/{id}

which resource is not existing at all

try accessing resource as /users/1234

EDIT:

create a class like

class RestResponse<T>{
private String status;
private String message;
private List<T> objectList;
//gettrs and setters
}

now in case you want response for User you can create it as following

RestResponse<User> resp = new RestResponse<User>();
resp.setStatus("400");
resp.setMessage("User does not exist");

and signature of your rest method would be like following

public RestResponse<User> getUser(@PathParam("id") int id)

while in case successful response you can set things like

RestResponse<User> resp = new RestResponse<User>();
List<User> userList = new ArrayList<User>();
userList.add(user);//the user object you want to return
resp.setStatus("200");
resp.setMessage("User exist");
resp.setObjectList(userList);