JavaWeb学习总结（六）—HttpServletResponse

Response概述：

response是Servlet.service方法的一个参数，类型为javax.servlet.http.HttpServletResponse。在客户端发出每个请求时，服务器都会创建一个response对象，并传入给Servlet.service()方法。response对象是用来对客户端进行响应的，这说明在service()方法中使response对象可以完成对客户端的响应工作。

response对象的功能分为以下四种：

设置响应头信息；

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" 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发送状态码；

　　　　> sendError(int sc) --> 发送错误状态码，例如404、500
　　　　> sendError(int sc, String msg) --> 也是发送错误状态码，还可以带一个错误信息！
　　　　> setStatus(int sc) --> 发送成功的状态码，可以用来发送302

aaarticlea/png;base64,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" alt="" />

3. 设置响应正文；

4. 重定向；

具体应用：

1.重定向

package zy.servlet;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class Aservlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        /*

         * 设置location响应头 ，实现请求重定向

         */

        //response.setHeader("Location","/JavaWeb/Bservlet");

        //设置服务器的响应状态码

        //response.setStatus(302);

        //快捷的重定向方式
　　　　 //response.sendRedirect(""http://www.baidu.com"");

        response.sendRedirect("/JavaWeb/Bservlet");
　　　　

    }

}

抓包可以看见：

服务器返回一个302状态码告诉浏览器，你要的资源我没有，但是我通过Location响应头告诉你哪里有，而浏览器解析响应头Location后知道要跳转到/JavaWeb/Bservlet页面，所以就会自动跳转到Bservlet。

2.设置refresh响应头，让浏览器定时刷新

package zy.servlet;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/*

 * 设置location响应头 ，实现请求重定向

 */

public class Cservlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        response.setContentType("text/html;charset=utf-8");

        response.getWriter().print("5s中后将跳转到百度主页");

        /*

         * 设置refresh响应头，让浏览器每隔3秒定时刷新

         * response.setHeader("refresh", "3");

         */

        //设置refresh响应头，让浏览器3秒后跳转到http://www.baidu.com

        response.setHeader("Refresh","5;URL=http://www.baidu.com");

        /*

         * 5秒跳转到Csevlet

        response.setHeader("Refresh","5;URL=/JavaWeb/Cservlet");

        */

    }

}

访问Cservlet，5秒将会跳转

3.禁用浏览器缓存

开发项目的时候浏览器的缓存会很讨厌，这时我们可以禁用它，可以参考indexjsp.

package zy.servlet;

import java.io.IOException;

import java.io.PrintWriter;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/*

 * 禁用浏览器缓存

 */

public class Dservlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        /*

         * 这三个响应头的设置可以禁用所有浏览器的缓存

         */

        response.setHeader("cache-control","no-cache");

        response.setHeader("pragma","no-cache");

        response.setDateHeader("expires",-1);

        response.getWriter().print("hello world");

    }

}

访问：

4.设置页面缓存

对于不经常变化的数据，在servlet中可以为其设置合理的缓存时间值，以避免浏览器频繁向服务器发送请求，提升服务器的性能。例如：

package zy.servlet;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class Eservlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String data = "helloworld";

        /**

         * 设置数据合理的缓存时间值，以避免浏览器频繁向服务器发送请求，提升服务器的性能

         * 这里是将数据的缓存时间设置为1天

         */

        response.setDateHeader("expires",System.currentTimeMillis() + 24 * 3600 * 1000);

        response.getOutputStream().write(data.getBytes());

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        this.doGet(request, response);

    }

}

访问页面，并查看响应头：

有8个小时的时差。

另外也可以在“C:\Users\zydev\AppData\Local\Microsoft\Windows\Temporary Internet Files”找到该文件，注意要打开隐藏文件夹选项才看得见。

Response的响应正文

response是响应对象，向客户端输出响应正文（响应体）可以使用response的响应流，repsonse一共提供了两个响应流对象：

1. PrintWriter out = response.getWriter()：获取字符流；

2. ServletOutputStream out = response.getOutputStream()：获取字节流

OutputStream流是字节流，可以处理任意类型的数据，而PrintWriter流是字符流，只能处理字符数据，如果用字符流处理字节数据，会导致数据丢失。

A. 相应图片字节流

package zy.servlet;

import java.io.FileInputStream;

import java.io.IOException;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import org.apache.commons.io.IOUtils;

/*

 * 演示响应字节数据

 */

public class Fservlet extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        String path = "D:/demo.jpg";

        FileInputStream in = new FileInputStream(path);

        //读取输入流的字节到字节数组中，IOUtis是Apache提供的一个工具jar包

        byte[] bytes = IOUtils.toByteArray(in);

        response.getOutputStream().write(bytes);

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        this.doGet(request, response);

    }

}

访问结果：

B. 下载图片

package com.web.study;

import java.io.FileInputStream;

import java.io.FileNotFoundException;

import java.io.IOException;

import java.io.InputStream;

import java.io.OutputStream;

import javax.servlet.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * 文件下载

 */

public class Bresponse extends HttpServlet {

    public void doGet(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        downloadFileByOutputStream(response);//下载文件，通过OutputStream流

    }

    /**

     * 下载文件，通过OutputStream流

     * @param response

     * @throws FileNotFoundException

     * @throws IOException

     */

    private void downloadFileByOutputStream(HttpServletResponse response)

            throws FileNotFoundException, IOException {

        //1.获取要下载的文件的绝对路径

        String realPath = this.getServletContext().getRealPath("/download/demo.jpg");

        //2.获取要下载的文件名

        String fileName = realPath.substring(realPath.lastIndexOf("\\")+1);

        //3.设置content-disposition响应头控制浏览器以下载的形式打开文件

        response.setHeader("content-disposition", "attachment;filename="+fileName);

        //4.获取要下载的文件输入流

        InputStream in = new FileInputStream(realPath);

        int len = 0;

        //5.创建数据缓冲区

        byte[] buffer = new byte[1024];

        //6.通过response对象获取OutputStream流

        OutputStream out = response.getOutputStream();

        //7.将FileInputStream流写入到buffer缓冲区

        while ((len = in.read(buffer)) > 0) {

        //8.使用OutputStream将缓冲区的数据输出到客户端浏览器

            out.write(buffer,0,len);

        }

        in.close();

    }

    public void doPost(HttpServletRequest request, HttpServletResponse response)

            throws ServletException, IOException {

        doGet(request, response);

    }

}

访问：

如果文件名是中文的：设置content-disposition响应头控制浏览器以下载的形式打开文件，中文文件名要使用URLEncoder.encode方法进行编码，否则会出现文件名乱码

 response.setHeader("content-disposition", "attachment;filename="+URLEncoder.encode(fileName, "UTF-8"));