We saw how a Servlet handles a Http Request that comes from a web browser here. We also saw that there are many doXXX() methods inside a Servlet that serve a specific purpose. In this chapter we are going look at the XXX part of the Servlet code.

So, lets get started!!!

The doXXX Methods

There are 3 main types of requests that get processed by a Servlet. They are:

• Get
• Post
• Put

Each of them have a corresponding doXXX() method in the Servlet class which would be:

• doGet
• doPost
• doPut

These methods are called by the service method in your Servlet.

Let us now take a look at a sample Servlet that has these 3 doXXX methods.

import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;

public class OurSecondServlet extends HttpServlet
{
    // doGet()
    public void doGet(HttpServletRequest request,
            HttpServletResponse response)
                    throws IOException, ServletException
                    {
        requestType("GET", response);
                    }

    // doPost()
    public void doPost(HttpServletRequest request,
            HttpServletResponse response)
                    throws IOException, ServletException
                    {
        requestType("POST", response);
                    }

    // doPut()
    public void doPut(HttpServletRequest request,
            HttpServletResponse response)
                    throws IOException, ServletException
                    {
        requestType("PUT", response);
                    }

    public void requestType(String requestType,
            HttpServletResponse response)
                    throws IOException, ServletException
                    {
        response.setContentType("text/html");

        PrintWriter out = response.getWriter();

        out.println("< html >");
        out.println("< head >");
        out.println("< title >Our Second Servlet" +
                "< / title >");
        out.println("< / head >");
        out.println("< body >");
        out.println("< h1 >Servlet Request< / h1 >");
        out.println("The Submitted Request type is : " + requestType);
        out.println("< / body >");
        out.println("< / html >");
                    }
}

How this code works?

As you can see, we have 3 different doXXX methods in our servlet, each of them calling the same method with just one parameter that differentiates them. Ideally in most cases, our code would be like this too. The logic that gets executed is mostly the same irrespective of the type of request submission. So, the doXXX methods, just receive the request, add some identifier that can be used to identify what request is submitted and then calls another method which will eventually be called by the other doXXX methods too.

The delegate method does the actual processing and returns the results.