检测ajax请求调用

Question

(I'm new to java world)

I'm learning dropwizard and I want to create resource that is returning view (html) or json depending on request type (ajax or not)

Example:

@Path("/")
public class ServerResource {

    @GET
    @Produces(MediaType.TEXT_HTML)
    public MainView getMainView() {
        return new MainView("Test hello world");
    }
}

How to add to this resource at the same Path JSON response if request is AJAX?

UPDATE 1. I created something like this:

@Path("/")
public class ServerResource {

    @GET
    @Consumes(MediaType.TEXT_HTML)
    @Produces(MediaType.TEXT_HTML)
    public MainView getMainView(@HeaderParam("X-Requested-With") String requestType) {
        return new MainView("hello world test!");
    }

    @GET
    @Consumes(MediaType.APPLICATION_JSON)
    @Produces(MediaType.APPLICATION_JSON)
    public List<String> getJsonMainView() {
        List<String> list = new ArrayList<String>();
        for (Integer i = 0; i < 10; i++) {
            list.add(i, "test" + i.toString());
        }
        return list;
    }
}

Looks like this is working as expected, but I know that is not a good practice.

Answer 1

Ajax requests USUALLY have (not always) X-Requested-With: XMLHttpRequest request header. See How to differentiate Ajax requests from normal Http requests?

The following code hasn't been tested.

@Path("/")
public class ServerResource {
    @GET
    @Produces({MediaType.TEXT_HTML, MediaType.APPLICATION_JSON})
    public MainView getMainView(@HeaderParam("X-Requested-With") String requestType) {
        if(requestType != null && requestType.equals("XMLHttpRequest")) {
           //The request is AJAX
        } else {
           //The request is not AJAX
        }
        ...
    }
}

Answer 2

There is no difference between AJAX-request and just request for the server. It's just GET, POST, PUT, DELETE or HEAD. If you want to separate output you should mark it somehow in the request itself by adding query parameter or use another URL or adding some header and then parsing in inside your processing method.

Hope that makes sense.