Java Servlet and Jquery

With Servlet you can either call the service method, so may be for your scenario you could pass the parameter to decide which method to invoke from doGet()

also you could identify if request is coming from AJAX using header check

There are other technologies available which will allow you directly invoke method See JSF, DWR

See

• How to invoke a method with Openfaces/JSF without rendering page?
• How to call a java method from jsp by clicking a menu in html page?

Personally I use reflection in my controllers(servlets) which basically let me achieve this.

If I have a servlet called UserController

The main url to call the servlet will be /user. Knowing this, I always pass my first parameter as ?action=add

Then in my servlet I have a method called add or actionAdd. Whichever you prefer.

Then I use the following code;

String str = String str = request.getParameter("action").toLowerCase();
Method method = getClass().getMethod(str, HttpServletRequest.class, HttpServletResponse.class);
method.invoke(this, request, response);

Explanation:

str will have the action parameters value, add in this case. Method method will be a reference to a method with the given name(str) and its expected parameter types.

I then invoke the method, passing the context, request and response.

The add method would look something like this;

public void add(HttpServletRequest request,HttpServletResponse response) throws ServletException, IOException { 
    //do add stuff

        String url = "/user/index.jsp";
        RequestDispatcher dispatcher = context.getRequestDispatcher(url);
        request.setAttribute("User", user);
        dispatcher.forward(request, response); 
}

I don't know about only passing back a string. But this should get you a basic idea.

Do note that reflection can cost you, altohugh it shouldnt really affect you much like this. And it is error prone as method names/signatures need to match perfectly.

So from jquery you would do an ajax request to the url:

 localhost/projectname/user/add (if you use urlrewrite)
 or
 localhost/projectname/user?action=add (if you dont)

Servlet Container supports Custom Http methods since Servlet 3.0. For Ex,

public void doHello(HttpServletRequest req, HttpServletResponse res) {
   //implement your custom method
}

The above method in Servlet can be invoked using hello http method.

But i am not sure if jquery has the support to invoke custom HTTP methods.

If it does not have, then the only option you have.

• Invoke Servlet using GET and action parameter.
• Read the action parameter and invoke the method using reflection.