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

 1 package com.xinqi.sevlet;
 2
 3 import java.io.IOException;
 4
 5 import javax.servlet.Servlet;
 6 import javax.servlet.ServletConfig;
 7 import javax.servlet.ServletException;
 8 import javax.servlet.ServletRequest;
 9 import javax.servlet.ServletResponse;
10
11 public class testServlet1 implements Servlet {
12
13     /**
14      * 销毁方法
15      */
16     public void destroy() {
17         System.out.println("这是销毁方法！");
18
19     }
20
21     /**
22      * 初始化方法
23      */
24     public void init(ServletConfig arg0) throws ServletException {
25         System.out.println("这是初始化方法！");
26     }
27
28     /**
29      * 服务方法
30      */
31     public void service(ServletRequest req, ServletResponse res) throws ServletException, IOException {
32
33         System.out.println("这是服务方法！");
34
35     }
36
37
38     //获取servlet配置信息
39     public ServletConfig getServletConfig() {
40
41         return null;
42     }
43
44     //获取servlet信息
45     public String getServletInfo() {
46
47         return null;
48     }
49 }

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

 1 package com.xinqi.sevlet;
 2
 3 import java.io.IOException;
 4
 5 import javax.servlet.GenericServlet;
 6 import javax.servlet.ServletException;
 7 import javax.servlet.ServletRequest;
 8 import javax.servlet.ServletResponse;
 9
10 public class testServlet2 extends GenericServlet{
11
12     @Override
13     public void service(ServletRequest arg0, ServletResponse arg1) throws ServletException, IOException {
14
15         System.out.println("这是服务方法！");
16     }
17
18 }

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

 1 package com.xinqi.sevlet;
 2
 3 import java.io.IOException;
 4
 5 import javax.servlet.ServletException;
 6 import javax.servlet.http.HttpServlet;
 7 import javax.servlet.http.HttpServletRequest;
 8 import javax.servlet.http.HttpServletResponse;
 9
10 public class testServlet3 extends HttpServlet{
11
12     @Override
13     protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
14
15         System.out.println("这是get方法提交");
16
17         doGet(req, resp);
18     }
19
20
21     @Override
22     protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
23         System.out.println("这是post方法提交");
24     }
25
26 }

配置文件的信息：

 1 <?xml version="1.0" encoding="UTF-8"?>
 2 <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">
 3   <display-name>servletPro</display-name>
 4
 5   <!-- sevlet配置 -->
 6   <!-- 1.servlet的定义：告诉容器如何来创建servlet -->
 7   <servlet>
 8       <servlet-name>test1</servlet-name>
 9       <servlet-class>com.xinqi.sevlet.testServlet1</servlet-class>
10   </servlet>
11
12   <!-- 2.配置servlet路径 servlet映射 -->
13   <!-- url-pattern 必须以/开头 访问：http://localhost:8080/servletPro/login  -->
14   <servlet-mapping>
15           <servlet-name>test1</servlet-name>
16           <url-pattern>/login</url-pattern>
17   </servlet-mapping>
18
19
20   <servlet>
21       <servlet-name>test2</servlet-name>
22       <servlet-class>com.xinqi.sevlet.testServlet2</servlet-class>
23   </servlet>
24   <servlet-mapping>
25           <servlet-name>test2</servlet-name>
26           <url-pattern>/login</url-pattern>
27   </servlet-mapping>
28
29
30   <servlet>
31       <servlet-name>test3</servlet-name>
32       <servlet-class>com.xinqi.sevlet.testServlet3</servlet-class>
33   </servlet>
34   <servlet-mapping>
35           <servlet-name>test3</servlet-name>
36           <url-pattern>/login</url-pattern>
37   </servlet-mapping>
38
39 </web-app>