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java ee 下载自己上传的文件，下载下来的内容只有大小，没内容

发布于 2021-12-06 08:15:17 字数 0 浏览 817 评论 9

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樱花落人离去 2021-12-06 17:35:43

大小怎么获得的？通过firebug之类的看到的？http请求除了我们常见和常用的get/post以外，head提交方式是仅获得http消息头，在消息头里面再获得content-length对应的消息头数据就是文件大小，你看看是不是以head方式提交的？要下载完整文件要以post方式提交，数据流返回格式默认是html，服务器会自动识别，不过严谨的方式还是手动指定为好

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眼泪淡了忧伤 2021-12-06 17:35:31

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>



<%@ taglib uri="http://java.sun.com/jsp/jstl/core" prefix="c" %>

<%

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

%>

<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>

<head>

<base href="<%=basePath%>">

<title>My JSP 'MyJsp.jsp' starting page</title>

<meta http-equiv="pragma" content="no-cache">

<meta http-equiv="cache-control" content="no-cache">

<meta http-equiv="expires" content="0">

<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">

<meta http-equiv="description" content="This is my page">

</head>

<body>

<hr>

<c:forEach items="${map }" var="filename">

${filename.key }<a href="${pageContext.request.contextPath }/DownloadServlet?filename=${filename.value}">下载</a><br>

<%-- ${filename.key }<a href="http://localhost:8080/day19Preview/DownloadServlet?filename=${filename.value}">下载</a><br> --%>

</c:forEach>

</body>

</html>

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柠檬 2021-12-06 17:35:22

package cx.fileUpload;

import java.io.File;

import java.io.FileInputStream;

import java.io.IOException;

import java.util.HashMap;

import java.util.Map;

import javax.servlet.ServletException;

import javax.servlet.ServletOutputStream;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

/**

* Servlet implementation class DownloadServlet

*/

@WebServlet("/DownloadServlet")

public class DownloadServlet extends HttpServlet {

private static final long serialVersionUID = 1L;

/**

*
@see HttpServlet#HttpServlet()

*/

public DownloadServlet() {

super();

// TODO Auto-generated constructor stub

}

/**

*
@see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)

*/

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

// TODO Auto-generated method stub

//response.getWriter().append("Served at: ").append(request.getContextPath());

File file =new File(this.getServletContext().getRealPath("WEB-INF/files"));

if(request.getParameter("filename" ) != null){

//获取参数对应的value

String filename =new String(request.getParameter("filename").getBytes("ISO8859-1"),"UTF-8");

int indexOf = filename.lastIndexOf("_");

String filename2 = filename.substring(indexOf+1);

//反推出文件路径

String path = CreateFileName.createFileName(filename2);

//拼接成最终下载路径

File downFile = new File(file,path+"/"+filename);

//输入与输出流

FileInputStream fileInputStream = new FileInputStream(downFile);

System.out.println(downFile+"downfile++++++++++");

//设置响应动作

response.setHeader("Content-Type", this.getServletContext().getMimeType(filename2));

response.setHeader("Content-Disposition", "attachment;filename="+filename2);

int len=0;

byte[] bs=new byte[2048];

ServletOutputStream outputStream = response.getOutputStream();

while((len=fileInputStream.read()) != -1) {

outputStream.write(bs, 0, len);

}

outputStream.flush();

outputStream.close();

fileInputStream.close();

}else {

//如果请求中不带参数，则显示所有文件

Map<String,String> map =new HashMap<String,String>();

//便利出所有文件

bianli(file,map);

request.setAttribute("map", map);

request.getRequestDispatcher("MyJsp.jsp").forward(request, response);

}

}

/**

*
@see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)

*/

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

// TODO Auto-generated method stub

doGet(request, response);

}

//找出文件中包含的所有文本，将文件路径和名字分别放在map中

public void bianli(File file,Map<String, String> map) {

File[] listFiles = file.listFiles();

for(File fl:listFiles) {

if(fl.isDirectory()) {

bianli(fl,map);

}else {

//文件路径

String absolutePath = fl.getAbsolutePath();

int lastIndexOf = absolutePath.lastIndexOf("/");

//包装的文件名

String filename = absolutePath.substring(lastIndexOf+1);

System.out.println(filename);

System.out.println(fl.getName()+"------------");

//真正的文件名

String nameLast=filename.substring(filename.indexOf("_")+1);

map.put(nameLast, fl.getName());

}

}

}

}