HelloWorld Servlet

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Servlet

HelloWorld Servlet

1.HelloServlet

package com.bjsxt;

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;

public class HelloServlet extends HttpServlet {

	@Override
	protected void service(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		super.service(req, resp); //这条语句的作用是首先会分发到doPost方法,然后执行完doPost方法后再往下执行，因为表单指定的是post方法
		resp.setContentType("text/html");
		PrintWriter out = resp.getWriter();
		out.println("<HTML>");
		out.println("  <HEAD><TITLE>A Servlet</TITLE></HEAD>");
		out.println("  <BODY>");
		out.print("    helloworld ");
		out.println("  </BODY>");
		out.println("</HTML>");
		out.flush();
		out.close();
		
	}

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		System.out.println("doGet...");
	}

	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		System.out.println("doPost..");
	}

}

2.index.jsp

<%@ page language="java" pageEncoding="UTF-8"%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
  <head>
    <title>Index</title>
  </head>
  
  <body>
    <form action="servlet/HelloServlet" method="post">
       <input type="text" name="test" />
       <input type="submit" value="提交" />
    </form>
  </body>
</html>

3.配置文件

<?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">
  <servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>HelloServlet</servlet-name>
    <servlet-class>com.bjsxt.HelloServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>HelloServlet</servlet-name>
    <url-pattern>/servlet/HelloServlet</url-pattern>
  </servlet-mapping>
  <welcome-file-list>
    <welcome-file>index.jsp</welcome-file>
  </welcome-file-list>
</web-app>

引用

如下图:

这里有两个service方法,第二个是从接口带过来的,第一个是HttpServlet自己添加的。
Dispatches client requests to the protected service method.
就是说第二个service方法会调用上图第一个service方法
以下是第一个service方法的英文解释:
Receives standard HTTP requests from the public service method and dispatches them to the doXXX methods defined in this class.
从public service方法中接收标准的http请求然后调用相应的doXXX方法

index.jsp中我写的是method=post,那么调用service的时候我写了个super.service(req, resp);这样的话前台页面输出helloworld,后台输出doPost...