Writing your first servlet by hand

one step

1. Inherit HttpServlet

2. Rewrite the doGet() or doPost() method

3. Register Servlet in web.xml

 

Two HttpServlet class inheritance diagram

 

 

Three examples

1. Create MyFirstServletDemo web project.

 

2. Edit index.jsp

<%@ page language = "java" import = "java.util.*" contentType="text/html; charset=utf-8"%>  

<%

String path = request.getContextPath();

String basePath = request.getScheme()+ "://" +request.getServerName()+ ":" +request.getServerPort()+path+ "/" ;

%>

 

<! DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

< html >

  < head >

    < base href = " <%= basePath %> " >

   

    < title > My JSP 'index.jsp' starting page </ title >

         < meta http-equiv = "pragma" content = "no-cache" >

         < meta http-equiv = "cache-control" content = "no-cache" >

         < meta http-equiv = "expires" content = "0" >    

         < meta http-equiv = "keywords" content = "keyword1,keyword2,keyword3" >

         < meta http-equiv = "description" content = "This is my page" >

         <!--

        <link rel =" stylesheet " type="text/ css " href ="styles.css">

        -->

  </ head >

 

  < body >

    < h1 > The first Servlet small example </ h1 >

    < a href = "servlet/HelloServlet" > Get方式请求HelloServlet </ a >

     < form action = "servlet/HelloServlet" method = "post" >

                 < input type = "submit" value = "Post方式请求HelloServlet" >

     </ form >

  </ body >

</ html >

3. Write HelloServlet

package servlet;

 

import java.io.IOException;

import java.io.PrintWriter;

 

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

 

//Inherited from HttpServlet

public class HelloServlet extends HttpServlet {

 

         @Override

         protected void doGet(HttpServletRequest request, HttpServletResponse response)

                         throws ServletException, IOException {

                 // TODO Auto-generated method stub

                System.out.println ( " Processing get() request..." );

                PrintWriter out = response.getWriter();

                response.setContentType( "text/html; charset=utf-8" );

                out.println( "<strong>Hello Servlet!</strong><br>" );

        }

 

         @Override

         protected void doPost(HttpServletRequest request, HttpServletResponse response)

                         throws ServletException, IOException {

                System.out.println ( " Processing post() request..." );

                PrintWriter out = response.getWriter();

                response.setContentType( "text/html; charset=utf-8" );

                out.println( "<strong>Hello Servlet!</strong><br>" );

        }

 

}

4. Write web.xml

<? xml version = "1.0" encoding = "UTF-8" ?>

< web-app version = "2.5"

         xmlns = " http://java.sun.com/xml/ns/javaee" ;

         xmlns:xsi = " http://www.w3.org/2001/XMLSchema-instance" ;

         xsi:schemaLocation = " http://java.sun.com/xml/ns/javaee

http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd" ; >

  < display-name ></ display-name >   

  < welcome-file-list >

    < welcome-file > index.jsp </ welcome-file >

  </ welcome-file-list >

  < servlet >

         < servlet-name > HelloServlet </ servlet-name >

         < servlet-class > servlet.HelloServlet </ servlet-class >

  </ servlet >

  < servlet-mapping >

         < servlet-name > HelloServlet </ servlet-name >

         < url-pattern > / servlet /HelloServlet </ url-pattern >

  </ servlet-mapping >

</ web-app >

 

Four running results