java web response提供文件下載功能

時間 2019-11-11

標籤 java web response 提供文件下載功能欄目 Java 简体版

原文原文鏈接

webapp項目的結構以下圖：javascript

download.html文件的內容以下：php

<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>Insert title here</title>
</head>
<body>
        <h1>資源下載:</h1>
       <p> 單純地使用a標籤時，只有瀏覽器不能解析的文件纔會是下載，不然將被瀏覽器直接解析。</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>所以，使用a標籤結合servlet的response指示瀏覽器不解析這些待下載文件</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>

負責處理下載的Servlet——download.java文件的內容以下：css

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.獲取請求下載的文件名
        String filename = request.getParameter("filename");

        //2.獲取文件的文件系統路徑
        String filePath = request.getServletContext().getRealPath("resource/"+filename);

        //3.設置響應頭，提示瀏覽器不要解析響應的文件數據，而是以附件(attachment)的形式解析，即下載功能
        response.setContentType(this.getServletContext().getMimeType(filename));
        response.setHeader("Content-Disposition", "attachment;filename="+filename);

        //4.讀取文件的 輸入流，以及響應的輸出流，並將數據輸出給客戶端
        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);
    }
}