response响应信息（重定向、定时刷新、设置响应类型、打开资源方式）
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：
<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
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;
/**
* content-type：响应头：设置当前响应的类型：html/xml/图片资源
*/
public class ResponseDemo3 extends HttpServlet {
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 设置编码格式
//response.setHeader("content-type","text/html;charset=utf-8");
// 简写方式
//response.setContentType("text/html;charset=utf-8");
// 当前向浏览器输出的格式支持html格式
//response.setContentType("text/html,charset=utf-8");
//response.getWriter().write("this is a html页面...");
// 当作自定义标签进行输出
response.setContentType("text/xml");
response.getWriter().write("this is a xml...");
}
protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
}
}
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：
