jsp页面转发到servlet

时间 2019-12-10

标签 jsp 页面转发 servlet 栏目 JSP 繁體版

原文原文链接

一个简单的例子来了解一下jsp页面转发到servlet的过程，环境 eclipse、tomcathtml

1.工程目录结构以下java

2.各部分代码以下web

1>index.jsptomcat

 1 <%@ page language="java" contentType="text/html; charset=utf-8"
 2     pageEncoding="utf-8"%>
 3 <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
 4 <html>
 5 <head>
 6 <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
 7 <title>首页</title>
 8 </head>
 9 <body>
10  <a href = "ForwardServlet">ForwardServlet</a><br>
11  <a href = "MyServlet">MyServlet</a>
12 </body>
13 </html>

2>web.xml服务器

<?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_2_5.xsd" id="WebApp_ID" version="2.5">
 <servlet>
    <servlet-name>ForwardServlet</servlet-name>
    <servlet-class>com.scd.servlet.ForwardServlet</servlet-class>
</servlet>
<servlet-mapping>
    <servlet-name>ForwardServlet</servlet-name>
    <url-pattern>/ForwardServlet</url-pattern>
</servlet-mapping>
  
  <servlet>
      <servlet-name>MyServlet</servlet-name>
      <servlet-class>com.scd.servlet.MyServlet</servlet-class>
  </servlet>
  <servlet-mapping>
      <servlet-name>MyServlet</servlet-name>
      <url-pattern>/MyServlet</url-pattern>
  </servlet-mapping>
</web-app>

3>ForwardServlet.javaapp

 1 package com.scd.servlet;
 2 
 3 import java.io.IOException;
 4 import javax.servlet.ServletException;
 5 import javax.servlet.annotation.WebServlet;
 6 import javax.servlet.http.HttpServlet;
 7 import javax.servlet.http.HttpServletRequest;
 8 import javax.servlet.http.HttpServletResponse;
 9 
10 /**
11  * Servlet implementation class ForwardServlet
12  */
13 //@WebServlet("/ForwardServlet")
14 public class ForwardServlet extends HttpServlet {
15     private static final long serialVersionUID = 1L;
16        
17     /**
18      * @see HttpServlet#HttpServlet()
19      */
20     public ForwardServlet() {
21         super();
22         // TODO Auto-generated constructor stub
23     }
24 
25     /**
26      * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
27      */
28     protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
29         // TODO Auto-generated method stub
30         System.out.println("My First Servlet!");
31     }
32 
33     /**
34      * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
35      */
36     protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
37         // TODO Auto-generated method stub
38         
39     }
40 
41 }

过程详解：当点击ForwardServlet链接时，请求到达服务器tomcat后，tomcat检查当前项目的web.xml中全部的<servlet-mapping></servlet-mapping>eclipse

配置中的<url-pattern></url-pattern>的属性值。看当中有没有一个和请求地址Forward相同。结果找到如，以下：jsp

<servlet-mapping>ui

<servlet-name>ForwardServlet</servlet-name>url

<url-pattern>/ForwardServlet</url-pattern>

</servlet-mapping>

其中 <url-pattern>/ForwardServlet</url-pattern> 是你访问地址

而后，tomcat找到和<servlet-mapping>相对应的<servlet-name>的<servlet>,根据<servlet-name>属性匹配, 找到了相同名字的

<servlet-name>ForwardServlet</servlet>

以下：

<servlet-name>ForwardServlet</servlet-name>

<servlet-class>com.scd.servlet.ForwardServlet</servlet-class>

</servlet>

根据上面的<servlet-class>找到Servlet文件ForwardServlet.class。

执行结果，在终端输出：

注意：在servlet中若是使用了注解@WebServlet("/ForwardServlet") ，那么在xml问件中就不须要配置该servlet的映射关系，若是二者都写了，开启服务器是会报错

The servlets named [ForwardServlet] and [com.scd.servlet.ForwardServlet] are both mapped to the url-pattern [/ForwardServlet] which is not permitted