servlet 的实现方法

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Servlet有三种实现方式：

* 实现Servlet接口

* 继承GenericServlet类

* 继承HttpServlet类

1.实现servlet类

package com.vc.servlet;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.Servlet;import javax.servlet.ServletConfig;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;public class HelloWorldServlet implements Servlet{//释放内存//1. reload//2. 关闭TomCat//3. 关机public void destroy() {// TODO Auto-generated method stubSystem.out.println("destroy it");}public ServletConfig getServletConfig() {// TODO Auto-generated method stubreturn null;}public String getServletInfo() {// TODO Auto-generated method stubreturn null;}//该 函数用于初始化，只会被调用一次（当用户第一次访问Servlet时，被调用）public void init(ServletConfig arg0) throws ServletException {// TODO Auto-generated method stubSystem.out.println("init it");}//用于处理业务逻辑，应该把业务逻辑代码写在该方法中//会被多次调用，当用户每访问一次时就会被调用一次//request用于获取客户端的信息//response用户向客户端返回信息public void service(ServletRequest request, ServletResponse response)throws ServletException, IOException {// TODO Auto-generated method stubSystem.out.println("service it");PrintWriter printWriter=response.getWriter();printWriter.println("<h1>"+"hello,world"+"</h1>");}}

2.继承 genericservlet

package com.vc.servlet;import java.io.IOException;import java.io.PrintWriter;import javax.servlet.GenericServlet;import javax.servlet.ServletException;import javax.servlet.ServletRequest;import javax.servlet.ServletResponse;@SuppressWarnings("serial")public class HelloWorldGenericServlet extends GenericServlet {@Overridepublic void service(ServletRequest request, ServletResponse response)throws ServletException, IOException {// TODO Auto-generated method stubtry{PrintWriter printWriter=response.getWriter();printWriter.println("<h1>hello,generic world.!!!</h1>");}catch(Exception e){e.printStackTrace();}}}

3.继承httpServlet

package com.vc.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;@SuppressWarnings("serial")public class HelloWorldHttpServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {// TODO Auto-generated method stubdoPost(req,resp);}@Overrideprotected void doPost(HttpServletRequest req, HttpServletResponse resp)throws ServletException, IOException {// TODO Auto-generated method stubPrintWriter printWriter=resp.getWriter();printWriter.println("<h1>Hello World!</h1>");}}

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