实现第一个Servlet程序(一)

(一)Servlet工作原理示意图

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(二)在Eclipse中创建Servlet应用程序的结构

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(三)在src目录下创建com.haha包，并在包下创建Demo类

package com.haha;import java.io.IOException;import javax.servlet.ServletException;import javax.servlet.annotation.WebServlet;import javax.servlet.http.HttpServlet;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;@WebServlet("/Demo")public class Demo extends HttpServlet {    private static final long serialVersionUID = 1L;    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        response.getWriter().append("Served at: ").append(request.getContextPath());    }    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        doGet(request, response);    }}

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(四)使用xml文件配置Demo类

 <?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">  <display-name>ServletDemo</display-name>  <welcome-file-list>    <welcome-file>index.html</welcome-file>    <welcome-file>index.htm</welcome-file>    <welcome-file>index.jsp</welcome-file>    <welcome-file>default.html</welcome-file>    <welcome-file>default.htm</welcome-file>    <welcome-file>default.jsp</welcome-file>  </welcome-file-list>  <servlet>      <!-- servlet-name名任意取 -->      <servlet-name>haha</servlet-name>      <!--servlet-class填写(包名.类名)  -->      <servlet-class>com.haha.Demo</servlet-class>  </servlet>  <servlet-mapping>      <servlet-name>haha</servlet-name>      <!-- Servlet资源路径名任意填写 -->      <url-pattern>/Demos</url-pattern>  </servlet-mapping></web-app>

(五)Servlet的多重映射
Servlet的多重映射指同一个Servlet可以被映射成多个虚拟路径，因此客户端可以通过多个路径对同一个Servlet进行访问。

 <?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://java.sun.com/xml/ns/javaee" xsi:schemaLocation="http://java.sun.com/xml/ns/javaee http://java.sun.com/xml/ns/javaee/web-app_3_0.xsd" id="WebApp_ID" version="3.0">  <display-name>ServletDemo</display-name>  <welcome-file-list>    <welcome-file>index.html</welcome-file>    <welcome-file>index.htm</welcome-file>    <welcome-file>index.jsp</welcome-file>    <welcome-file>default.html</welcome-file>    <welcome-file>default.htm</welcome-file>    <welcome-file>default.jsp</welcome-file>  </welcome-file-list>  <servlet>      <!-- servlet-name名任意取 -->      <servlet-name>haha</servlet-name>      <!--servlet-class填写(包名.类名)  -->      <servlet-class>com.haha.Demo</servlet-class>  </servlet>  <servlet-mapping>      <servlet-name>haha</servlet-name>      <!-- Servlet的多重映射 -->      <url-pattern>/Demos</url-pattern>      <url-pattern>/abc</url-pattern>      <url-pattern>/abcde</url-pattern>  </servlet-mapping></web-app>

(六)运行结果