如何从HttpServlet调用RemoteServiceServlet中的方法？

Question

I am using GWT and want to be able to invoke the method incrementProduct(String productName) in my main RemoteServiceServlet by typing this URL in my browser:

http://mywebshop.appspot.com/increment?name=pillow

To handle this request I've created the following HttpServlet:

public class IncrementServlet extends HttpServlet {

    @Override
    protected void doGet(HttpServletRequest request,
            HttpServletResponse response) throws ServletException, IOException {
        System.out.println("IncrementServlet called!");
        String name = request.getParameter("name");
        // Call MyRemoteServiceServlet.incrementProduct(name) somehow
    }
}

and added this to web.xml:

<servlet>
    <servlet-name>IncrementServlet</servlet-name>
    <servlet-class>x.y.z.IncrementServlet</servlet-class>
</servlet>

<servlet-mapping>
    <servlet-name>IncrementServlet</servlet-name>
    <url-pattern>/increment</url-pattern>
</servlet-mapping>

• Question 1 : Is this a sensible approach?
• Question 2 : How do I go about invoking incrementProduct() from the HttpServlet?

Answer 1

I happened to overlook one important fact that solved my problem:

• RemoteServiceServlet inherits HttpServlet !

So I simply implemented doGet() in my RemoteServiceServlet like this:

@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
        throws ServletException, IOException {

    switch (req.getServletPath()) {
    case "/increment":
        incrementProduct(req.getParameter("name"));
        break;
    }
}

And replaced IncrementServlet in web.xml with this:

<servlet-mapping>
    <servlet-name>MyRemoteServiceServlet</servlet-name>
    <url-pattern>/increment</url-pattern>
</servlet-mapping>

Which allows me to invoke incrementProduct(...) by entering this URL in a browser:

http://mywebshop.appspot.com/increment?name=pillow

which is exactly what I wanted! There simply was no need for another HttpServlet :)

Answer 2

Question 1 In general as an classic servlet code this is fine. As GWT application it does not use anything from GWT.

Question 2 GWT will generate all the servlet code, you do not have to wrap it inside another servlet(IncrementServlet). To turn this into a GWT application you have to implement AsyncCallback on client side entry point(onModuleLoad()) and on server side you must implement RemoteServiceServlet as you did already, what's missing now is the binding part - an interface definition extending RemoteService with a method having similar signature as your service method. Normally GWT plugin in any IDE would generate the binding part, if not then you can do it manually. See GWT documentation with step by step guide. https://developers.google.com/web-toolkit/doc/1.6/DevGuideServerCommunication

Note that async rpc is a bit old and has some drawbacks. GWT now has RequestFactory concept, but for your use case I would say it is a big overhead.