response响应信息（重定向、定时刷新、设置响应类型、打开资源方式）

xiaoxiao2022-07-12 173

Response

响应信息通过状态码：判断响应是否成功

Status：

200 -----成功响应 500 -----服务器出现了异常（servlet（和业务相关的数据）由 tomcat） 404 -----请求 url 路径有问题 302 -----进一步请求

响应头： loaction：一个地址 + 302：重定向简写方式：response。sendRedirect (".项目名称/hello.html")

重定向的特点：

发送了两次请求（产生两个 request 对象）request：本身域对象（共享数据）

重定向 / 请求转发（servletContext对象）跳转页面 refersh：定时刷新或者经过 n 秒跳转页面响应头（已下载方式打开）文件下载：使用第三方 jar 包 commons-io

1. 重定向的原理

重定向——>过程中。有几个request对象？请求转发——>过程中，有几个request对象？

package com.github.urlpattern; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; public class MappingDemo1 extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("mappingDemo1.doGet()方法调用了..."); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } }

package com.github.urlpattern; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; public class MappingDemo2 extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("mappingDemo2.doGet()方法调用了..."); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } }

响应头：loaction + status(302) -------进一步请求重定向：原理：location + 302

adv.html：

<!DOCTYPE html> <html lang="en"> <head> <meta charset="UTF-8"> <title>广告页面</title> </head> <body> 广告页面<br> <a href="/RequestDemo5">跳转到资源地址</a> </body> </html> package com.github.response; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; /** * 请求重定向 * location请求头+302状态码 */ public class ResponseDemo1 extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 重定向的原理： // 设置状态302 // 1. // response.setStatus(302); // 进一步请求服务器 // // 设置location响应头 // response.setHeader("location","/adv.html"); // 2. // 简便的方法 response.sendRedirect("/adv.html"); // 3. // 地址栏不会发生变法，服务器行为 //request.getRequestDispatcher("/adv.html").forward(request,response); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } }

地址栏输入：回车之后：

2. refersh：响应头定时刷新，每隔n秒跳转资源

package com.github.response; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.IOException; /** * refersh：响应头定时刷新，每隔n秒跳转资源 */ public class ResponseDemo2 extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { response.setContentType("text/html;charset=utf-8"); // 1. // 设置响应头：每经过多少秒实现页面刷新 //response.setHeader("refersh","2"); // 2. response.getWriter().write("注册成功！3秒后跳转首页"); response.setHeader("refresh","3;/adv.html"); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } }

3秒之后刷新页面，重定向到一个新的页面：adv.html：

3. content-type：响应头：设置当前响应的类型：html/xml/图片资源

4. Content-Disposition: attachment; filename=aaa.zip ---- 以下载方式打开资源

package com.github.response; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import java.io.*; /** * Content-Disposition: attachment; filename=aaa.zip * ---- 以下载方式打开资源 */ public class ResponseDemo4 extends HttpServlet { protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { // 1. // 下载文件 // 创建一个字节输入流对象 // InputStream in = new FileInputStream("C:\\Users\\28187\\Pictures\\Saved Pictures\\壁纸\\574.jpg"); // // 获取一个字节输出流对象 // OutputStream out = response.getOutputStream(); // // 边读边写 // byte[] buff = new byte[1024]; // int len = 0; // while ((len=in.read(buff)) != -1) { // out.write(buff,0,len); // } // // 释放资源 // in.close(); // out.close(); // 2. // 创建File对象 File file = new File("C:\\Users\\28187\\Pictures\\Saved Pictures\\壁纸\\574.jpg"); // Content-Disposition:响应头 response.setHeader("Content-Disposition","attachment;filename="+file.getName()); // 下载文件 // 创建一个字节输入流对象 InputStream in = new FileInputStream("C:\\Users\\28187\\Pictures\\Saved Pictures\\壁纸\\574.jpg"); // 获取一个字节输出流对象 OutputStream out = response.getOutputStream(); // 边读边写 byte[] buff = new byte[1024]; int len = 0; while ((len=in.read(buff)) != -1) { out.write(buff,0,len); } // 释放资源 in.close(); out.close(); } protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { } }

直接开始下载内容：

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