演示Servlet

package com.demo.servlet;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

//每一个servlet都是继承HttpServlet类
public class LoginServlet extends HttpServlet {

	//doGet方法处理get方法请求(访问该Servlet时，如果没有指定则默认执行此方法)
	public void doGet(HttpServletRequest request,HttpServletResponse response){
		
		System.out.println("doGet()...");
		//修改字符编码
		response.setContentType("text/html;charset=GBK	");
		try {
			PrintWriter out=response.getWriter();
			out.println("成功访问并执行Servlet...");
			//清空缓冲区
			out.flush();
			//关闭PrintWriter
			out.close();
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
	//doPost方法处理post方法请求
	public void doPost(HttpServletRequest request,HttpServletResponse response){
		
		System.out.println("doPos()...");
		//修改字符编码
		response.setContentType("text/html;charset=GBK	");
		try {
			PrintWriter out=response.getWriter();
			String username=request.getParameter("username");
			String password=request.getParameter("password");
			if(username.equals("admin")&&password.equals("123456")){
				out.println("登陆成功");
			}else{
				out.println("登陆失败");
			}
			//清空缓冲区
			out.flush();
			//关闭PrintWriter
			out.close();
		} catch (Exception e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
	}
	
//	//重新无参的init()
//	public void init() throws ServletException{
//		
//		System.out.println("无参i初始化方法nit()...");
//	}
	
	//重新有参的init()
	public void init(ServletConfig config) throws ServletException{
		//必须调用父类的init方法
		super.init(config);
		System.out.println("有参初始化方法init()...");
		//获取初始化参数
		System.out.println("初始化参数的值:"+config.getInitParameter("paramName"));
	}
}

package com.demo.web.utils;

import java.io.IOException;
import java.io.PrintWriter;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class LifeCycleServlet extends HttpServlet {

	private ServletConfig config;
	private String name;
	public void init() throws ServletException {
		System.out.println("init()方法被调用...");
		// 获取ServletConfig对象
		config = this.getServletConfig();
		// 获取初始化参数
		name = config.getInitParameter("name");
	}
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//设置页面编码
		response.setContentType("text/html;charset=GBK");
		PrintWriter out=response.getWriter();
		System.out.println("doGet()方法被调用一次...");
		out.println("<font color=green>");
		out.println("祝贺 "+name+" 学会编写第一个Servlet!");
		out.println("</font>");
		out.flush();
		out.close();
	}
}

<?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>LifeCycleServlet</servlet-name>
		<servlet-class>com.demo.web.utils.LifeCycleServlet</servlet-class>
		<init-param>
			<param-name>name</param-name>
			<param-value>熊佳佳</param-value>
		</init-param>
	</servlet>
	<servlet-mapping>
		<servlet-name>LifeCycleServlet</servlet-name>
		<url-pattern>/LifeCycleServlet</url-pattern>
	</servlet-mapping>
</web-app>

信息: Server startup in 923 ms
init()方法被调用...
doGet()方法被调用一次...
doGet()方法被调用一次...
doGet()方法被调用一次...
doGet()方法被调用一次...