10-Redirect重定向
10-Redirect重定向
概述
本文主要讲解重定向，什么是重定向，重定向（redirect）和我们之前学的转发（diapatcher）有什么相同和不同之处呢？
重定向
重定向是通过各种方法将各种网络请求重新定个方向转到其他位置
请求转发
请求转发是在web服务器内部，将请求从一个servlet转到另一个servlet
重定向VS请求转发
- 重定向浏览器是发送两次请求，而请求转发浏览器只发一次请求
- 重定向浏览器地址发生变化，请求转发则浏览器地址不变
- 重定向是从浏览器发送出去的，请求可以使用request域对象
- 重定向没有request域对象，而请求转发可以使用request域对象
- 重定向可以去请求在本网站外部的资源，请求转发是在web服务器内部，不能请求本网站外的资源
实践
请求转发示例参见转发
本实践需要接上一篇
新增以下文件或配置
RedirectServlet.java
package com.kuang.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 功能描述
*
* @since 2022-08-15
*/
public class RedirectServlet extends HttpServlet {
private static final long serialVersionUID = -1351713222498041389L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
resp.sendRedirect("/s4/image");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee
https://jakarta.ee/xml/ns/jakartaee/web-app_5_0.xsd"
version="5.0"
metadata-complete="true">
<servlet>
<servlet-name>image</servlet-name>
<servlet-class>com.kuang.servlet.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>image</servlet-name>
<url-pattern>/image</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>redirect</servlet-name>
<servlet-class>com.kuang.servlet.RedirectServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>redirect</servlet-name>
<url-pattern>/redirect</url-pattern>
</servlet-mapping>
</web-app>
再一个jsp的小例子
RequestTest.java
package com.kuang.servlet;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import java.io.IOException;
/**
* 功能描述
*
* @since 2022-08-15
*/
public class RequestTest extends HttpServlet {
private static final long serialVersionUID = 6521499379637028043L;
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
String username = req.getParameter("username");
String password = req.getParameter("password");
System.out.println(username + ":" + password);
resp.sendRedirect("/s4/success.jsp");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}
}
index.jsp
<html>
<body>
<h2>Hello World!</h2>
<form action="${pageContext.request.contextPath}/login" method="get">
用户名：<input type="text" name="username"> <br>
密码：<input type="password" name="password"> <br>
<input type="submit">
</form>
</body>
</html>
success.jsp
<html>
<body>
<h2>Success</h2>
</body>
</html>
web.xml
<?xml version="1.0" encoding="UTF-8"?>
<!--
Licensed to the Apache Software Foundation (ASF) under one or more
contributor license agreements. See the NOTICE file distributed with
this work for additional information regarding copyright ownership.
The ASF licenses this file to You under the Apache License, Version 2.0
(the "License"); you may not use this file except in compliance with
the License. You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
-->
<web-app xmlns="https://jakarta.ee/xml/ns/jakartaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="https://jakarta.ee/xml/ns/jakartaee
https://jakarta.ee/xml/ns/jakartaee/web-app_5_0.xsd"
version="5.0"
metadata-complete="true">
<servlet>
<servlet-name>image</servlet-name>
<servlet-class>com.kuang.servlet.ImageServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>image</servlet-name>
<url-pattern>/image</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>redirect</servlet-name>
<servlet-class>com.kuang.servlet.RedirectServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>redirect</servlet-name>
<url-pattern>/redirect</url-pattern>
</servlet-mapping>
<servlet>
<servlet-name>req</servlet-name>
<servlet-class>com.kuang.servlet.RequestTest</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>req</servlet-name>
<url-pattern>/login</url-pattern>
</servlet-mapping>
</web-app>
在登录页面输入用户名密码后会跳转到成功页面
