java web response提供文件下载功能

时间：2023-03-09 12:55:11
java web response提供文件下载功能

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webapp项目的结构如下图：

java web response提供文件下载功能

download.html文件的内容如下：

<!DOCTYPE html>

<html>

<head>

<meta charset="UTF-8">

<title>Insert title here</title>

</head>

<body>

        <h1>资源下载:</h1>

       <p> 单纯地使用a标签时，只有浏览器不能解析的文件才会是下载，否则将被浏览器直接解析。</p>

        <a href="/WEB/resource/a.mp3" >a.mp3</a><br>

        <a href="/WEB/resource/a.exe" >a.exe</a><br>

        <a href="/WEB/resource/a.txt" >a.txt</a><br>

        <a href="/WEB/resource/a.xlsx" >a.xlsx</a><br>

        <a href="/WEB/resource/a.png" >a.png</a><br>

        <p>因此，使用a标签结合servlet的response指示浏览器不解析这些待下载文件</p>

        <a href="/WEB/download?filename=a.mp3" >a.mp3</a><br>

        <a href="/WEB/download?filename=a.exe" >a.exe</a><br>

        <a href="/WEB/download?filename=a.txt" >a.txt</a><br>

        <a href="/WEB/download?filename=a.xlsx" >a.xlsx</a><br>

        <a href="/WEB/download?filename=a.png" >a.png</a><br>

</body>

</html>

负责处理下载的Servlet——download.java文件的内容如下：

package com.download.servlet;

import java.io.FileInputStream;

import java.io.IOException;

import java.io.InputStream;

import javax.servlet.ServletException;

import javax.servlet.ServletOutputStream;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

 * Servlet implementation class Download

 */

public class Download extends HttpServlet {

    private static final long serialVersionUID = 1L;

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        //1.获取请求下载的文件名

        String filename = request.getParameter("filename");

        //2.获取文件的文件系统路径

        String filePath = request.getServletContext().getRealPath("resource/"+filename);

        //3.设置响应头，提示浏览器不要解析响应的文件数据，而是以附件(attachment)的形式解析，即下载功能

        response.setContentType(this.getServletContext().getMimeType(filename));

        response.setHeader("Content-Disposition", "attachment;filename="+filename);

        //4.读取文件的 输入流，以及响应的输出流，并将数据输出给客户端

        InputStream in = new FileInputStream(filePath);

        ServletOutputStream out = response.getOutputStream();

        int len = 0;

        byte[] buf = new byte[1024];

        while((len=in.read(buf))!=-1) {

            out.write(buf, 0, len);

        }

        in.close();

    }

    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

        doGet(request, response);

    }

}

在浏览器地址栏中输入http://localhost:8080/DownloadServlet/download.html。

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