Servlet实现的三种方式

实现Servlet的三种方式：一个实现，两个继承

/*==========================================
* servlet的执行过程：
* 1.创建servlet对象（Tomcat执行）
* 2.第一次访问servlet时执行
* init()方法 该方法只执行一次
* service()方法
* 3.之后每访问一次 就执行一次service()方法
* 4.关闭服务时调用destroy()方法 该方法只执行一次
*servlet的服务周期
*1.创建
*2.初始化
*3.服务
*4.销毁
*
*/

第一种方法，实现Servlet接口

package com.xinqi.sevlet;

import java.io.IOException;

import javax.servlet.Servlet;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class testServlet1 implements Servlet {

    /**
     * 销毁方法
     */
    public void destroy() {
        System.out.println("这是销毁方法！");
        
    }
    
    /**
     * 初始化方法
     */
    public void init(ServletConfig arg0) throws ServletException {
        System.out.println("这是初始化方法！");
    }

    /**
     * 服务方法
     */
    public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
        
        System.out.println("这是服务方法！");
        
    }

    
    //获取servlet配置信息
    public ServletConfig getServletConfig() {
        
        return null;
    }

    //获取servlet信息
    public String getServletInfo() {
        
        return null;
    }
}

第二种方法：继承GenericServlet抽象类

GenericServlet抽象类中只有一个抽象方法service()方法

public abstract class GenericServletextends java.lang.Objectimplements Servlet, ServletConfig, java.io.Serializable

package com.xinqi.sevlet;

import java.io.IOException;

import javax.servlet.GenericServlet;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

public class testServlet2 extends GenericServlet{

    @Override
    public void service(ServletRequest arg0, ServletResponse arg1) throws ServletException, IOException {
        
        System.out.println("这是服务方法！");
    }

}

第三种方式：继承HttpServlet抽象类重写doPut()和doPost()方法

public abstract class HttpServletextends GenericServletimplements java.io.Serializable

package com.xinqi.sevlet;

import java.io.IOException;

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

public class testServlet3 extends HttpServlet{

    @Override
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

        System.out.println("这是get方法提交");
        
        doGet(req, resp);
    }
    

    @Override
    protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
        System.out.println("这是post方法提交");
    }

}

配置文件的信息：

<?xml version="1.0" encoding="UTF-8"?>
<web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1">
  <display-name>servletPro</display-name>
  
  <!-- sevlet配置 -->
  <!-- 1.servlet的定义：告诉容器如何来创建servlet -->
  <servlet>
      <servlet-name>test1</servlet-name>
      <servlet-class>com.xinqi.sevlet.testServlet1</servlet-class>
  </servlet>
  
  <!-- 2.配置servlet路径 servlet映射 -->
  <!-- url-pattern 必须以/开头 访问：http://localhost:8080/servletPro/login  -->
  <servlet-mapping>
          <servlet-name>test1</servlet-name>
          <url-pattern>/login</url-pattern>
  </servlet-mapping>
  
  
  <servlet>
      <servlet-name>test2</servlet-name>
      <servlet-class>com.xinqi.sevlet.testServlet2</servlet-class>
  </servlet>
  <servlet-mapping>
          <servlet-name>test2</servlet-name>
          <url-pattern>/login</url-pattern>
  </servlet-mapping>


  <servlet>
      <servlet-name>test3</servlet-name>
      <servlet-class>com.xinqi.sevlet.testServlet3</servlet-class>
  </servlet>
  <servlet-mapping>
          <servlet-name>test3</servlet-name>
          <url-pattern>/login</url-pattern>
  </servlet-mapping>
  
</web-app>