Servlet三种实现方式

Servlet三种实现方式：实现Servlet接口，继承GenericServlet ，继承HttpServlet。

1、实现Servlet接口：

import javax.servlet.*;
import java.io.*;

public class Hello implements Servlet{
    //执行条件：reload，关闭tomcat，关机
    public void destroy() {
        // TODO Auto-generated method stub
        System.out.println("destroy it");
    }
    @Override
    public ServletConfig getServletConfig() {
        // TODO Auto-generated method stub
        return null;
    }
    @Override
    public String getServletInfo() {
        // TODO Auto-generated method stub
        return null;
    }
    //初始化，用户第一次访问时调用
    public void init(ServletConfig arg0) throws ServletException {
        // TODO Auto-generated method stub
        System.out.println("init it");
    }
    //业务处理
    public void service(ServletRequest req, ServletResponse res)
            throws ServletException, IOException {
        // TODO Auto-generated method stub
        System.out.println("service it");
        res.getWriter().println("hell,world");
    }
}

2、继承GenericServlet ：

import javax.servlet.*;
import java.io.*;

public class HelloGen extends GenericServlet{

    @Override
    public void service(ServletRequest req, ServletResponse res)
            throws ServletException, IOException {
        // TODO Auto-generated method stub
        res.getWriter().println("Hello,gen");        
    }
}

3、继承HttpServlet：

import javax.servlet.*;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.*;

public class HellHttp extends HttpServlet {
 public void doGet(HttpServletRequest req,HttpServletResponse res)
 {
     try {
         res.setContentType("text/html;charset=gbk");
         
         res.getWriter().println("hello,HttpServlet");;
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }     
 }
 public void doPost(HttpServletRequest req,HttpServletResponse res)
 {
     this.doGet(req, res);     
 }
}

 使用Servlet需要对其在web.xml中进行配置，对于上面的三种方式要在web.xml中添加如下信息：

<!-- JSPC servlet mappings start-->
 <servlet>
    <servlet-name>hello</servlet-name>
    <servlet-class>Hello</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>hello</servlet-name>
      <url-pattern>/hello</url-pattern>
  </servlet-mapping>
<!-- JSPC hellogen-->
 <servlet>
    <servlet-name>hellogen</servlet-name>
    <servlet-class>HelloGen</servlet-class>
  </servlet>
  <servlet-mapping>
    <servlet-name>hellogen</servlet-name>
      <url-pattern>/hellogen</url-pattern>
  </servlet-mapping>
<!-- JSPC hellohttp-->
 <servlet>
    <servlet-name>hellohttp</servlet-name>
    <servlet-class>HellHttp</servlet-class>
  </servlet>
  <servlet-mapping>
  <servlet-name>hellohttp</servlet-name>
      <url-pattern>/hellohttp</url-pattern>
  </servlet-mapping>
<!-- JSPC servlet mappings end-->

启动tomcat，输入正确地址，即可在浏览器中访问了。