开发servlet的三种方法

 1 import javax.servlet.*;
 2 import javax.servlet.ServletConfig;
 3 import javax.servlet.ServletException;
 4 import javax.servlet.ServletRequest;
 5 import javax.servlet.ServletResponse;
 6 import java.io.IOException;
 7 
 8 //使用servlet接口方式开发
 9 import javax.servlet.*;
10 import java.io.*;
11 
12 public class Hello  implements Servlet {
13         
14     //该函数用于初始化该servlet（类似于类的构造函数）
15     //该函数只会被调用一次（当用户第一次访问该servlet时被调用）
16     public void init(ServletConfig parm1) throws ServletException {
17     }
18 
19     public ServletConfig getServletConfig() {
20         return null;
21     }
22 
23     //该函数用于处理业务逻辑
24     //应当把业务逻辑代码写在这个函数中
25     //用户每次访问该servlet时。都会调用
26     //req用于获得客户端信息，res用于向客户端返回信息
27     public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
28         System.out.println("service it");
29         PrintWriter pw=res.getWriter();
30         pw.println("hello,world");
31     }
32 
33     public String getServletInfo() {
34         return "";
35     }
36 
37     public void destroy() {
38         //销毁servlet实例
39         //reload、关闭tomcat时会调用
40     }
41 }

 1 import javax.servlet.GenericServlet;
 2 import javax.servlet.*;
 3 import java.io.*;
 4 
 5 public class HelloGen extends GenericServlet{
 6     public void service(ServletRequest req,ServletResponse res){
 7     
 8     try{
 9         PrintWriter pw=res.getWriter();
10         pw.println("Hello,world! generic");
11     }
12     catch(Exception e){
13         e.printStackTrace();
14     }
15     }
16 }

 1 public class HelloHttp extends HttpServlet{
 2     
 3     public void doGet(HttpServletRequest req,HttpServletResponse res){
 4         try{
 5             PrintWriter pw=res.getWriter();
 6             pw.println("Hello,http");
 7         }
 8         catch(Exception e){
 9             e.printStackTrace();
10         }
11     }
12     
13     public void doPost(HttpServletRequest req,HttpServletResponse res){
14         this.doGet(req,res);
15     }
16 }