【转】HTML5拖拽文件到浏览器并实现文件上传下载

最新推荐文章于 2024-08-20 15:46:47 发布

转载最新推荐文章于 2024-08-20 15:46:47 发布 · 1k 阅读

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本文介绍了一个使用JSP实现的文件上传与下载功能的示例，包含前端页面设计与后端处理逻辑。前端利用HTML和JavaScript实现了文件选择与拖拽上传的功能，后端通过Tomcat服务器和Servlet进行文件的接收与存储。

先上代码，写的jsp页面，后台是tomcat服务器，所以页面里有一些java的代码，如果后台用其他语言可以无视：

<%@ page language="java" contentType="text/html; charset=UTF-8"
pageEncoding="UTF-8"%>
<%@page import="java.io.*"%>
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<title>上传、下载文件</title>
<style type="text/css">
#filedrag {
display: none;
font-weight: bold;
text-align: center;
padding: 1em 0;
margin: 1em 0;
color: #555;
border: 2px dashed #555;
border-radius: 7px;
cursor: default;
}

#filedrag.hover {
color: #f00;
border-color: #f00;
border-style: solid;
box-shadow: inset 0 3px 4px #888;
}
</style>
</head>
<body>
<form id="upload" action="UploadServlet" enctype="multipart/form-data"
  method="post" onsubmit="return upLoad();">
  <p>
   <label for="fileselect">file name:</label><input multiple="true"
    type="file" id="fileselect" name="fileselect[]" />
  <div id="filedrag">或者将文件拖拽到这里</div>
  <div id="submitbutton">
   <input type="submit" value="提交">
  </div>
</form>
<div id="messages">
</div>
<% //java代码，显示服务器上可以供下载的文件
  File f = new File("G://defggg/");
  File[] list = f.listFiles();
  for (int i = 0; i < list.length; ++i) {
   System.out.println(list[i].getName());
   out.print("<a href='DownloadServlet?filename="
     + list[i].getName() + "'>" + list[i].getName()
     + "</a><br/>");
  }
%>
<script type="text/javascript">
  var upfiles = new Array();
  // getElementById
  function $id(id) {
   return document.getElementById(id);
  }

  // output information
  function Output(msg) {
   var m = $id("messages");
   m.innerHTML = msg + m.innerHTML;
  }

  // file drag hover
  function FileDragHover(e) {
   e.stopPropagation();
   e.preventDefault();
   e.target.className = (e.type == "dragover" ? "hover" : "");
  }

// file selection
function FileSelectHandler(e) {

// cancel event and hover styling
FileDragHover(e);

// fetch FileList object
var files = e.target.files || e.dataTransfer.files;

   // process all File objects
   for ( var i = 0, f; f = files[i]; i++) {
    ParseFile(f);
    upfiles.push(f);
   }

}

// output file information
function ParseFile(file) {

   Output("<p>文件信息: <strong>" + file.name
     + "</strong> 类型: <strong>" + file.type
     + "</strong> 大小: <strong>" + file.size
     + "</strong> bytes</p>");
  }
  function upLoad() {
   if (upfiles[0]) {
    var xhr = new XMLHttpRequest();   //Ajax异步传输数据
    xhr.open("POST", "UploadServlet", true);
    var formData = new FormData();
    for ( var i = 0, f; f = upfiles[i]; i++) {
     formData.append('myfile', f);
    }
    xhr.send(formData);
    xhr.onreadystatechange=function(e){
     history.go(0); //由于这个页面还要显示可以下载的文件，所以需要刷新下页面
    }
    return false;
   }
  }
  // initialize
  function Init() {

var fileselect = $id("fileselect"), filedrag = $id("filedrag"), submitbutton = $id("submitbutton");

// file select
fileselect.addEventListener("change", FileSelectHandler, false);

   // is XHR2 available?
   var xhr = new XMLHttpRequest();
   if (xhr.upload) {

    // file drop
    filedrag.addEventListener("dragover", FileDragHover, false);
    filedrag.addEventListener("dragleave", FileDragHover, false);
    filedrag.addEventListener("drop", FileSelectHandler, false);
    filedrag.style.display = "block";
    // remove submit button
    //submitbutton.style.display = "none";
   }

}

  // call initialization file
  if (window.File && window.FileList && window.FileReader) {
   Init();
  }
</script>
</body>
</html>

附上后台处理上传下载的servlet，用了smartUpLoad，不能很好的解决中文问题：

package com.hit.software;

import java.io.IOException;

import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.jspsmart.upload.Files;
import com.jspsmart.upload.SmartUpload;

/**
* Servlet implementation class UploadServlet
*/
@WebServlet("/UploadServlet")
public class UploadServlet extends HttpServlet {
private static final long serialVersionUID = 1L;
private ServletConfig config;

final public void init(ServletConfig config) throws ServletException {
this.config = config;
}

/**
* @see HttpServlet#HttpServlet()
*/
public UploadServlet() {
super();
// TODO Auto-generated constructor stub
}

/**
* @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse
*      response)
*/
protected void doGet(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {
  doPost(request, response);
}

/**
* @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse
*      response)
*/
protected void doPost(HttpServletRequest request,
   HttpServletResponse response) throws ServletException, IOException {
  request.setCharacterEncoding("UTF-8");
  // String s = request.getParameter("pic");
  // System.out.println(s);
  SmartUpload mySmartUpload = new SmartUpload();
  try {
   mySmartUpload.initialize(config, request, response);
   mySmartUpload.setMaxFileSize(150 * 1024 * 1024);
   mySmartUpload.setTotalMaxFileSize(150 * 1024 * 1024);
   // mySmartUpload.setAllowedFilesList("doc,txt,rar,pdf,png");
   mySmartUpload.setDeniedFilesList("exe");
   mySmartUpload.upload();
   Files f = mySmartUpload.getFiles();
   int size = f.getCount();
   for (int i = 0; i < size; ++i) {
    String fileName = mySmartUpload.getFiles().getFile(i)
      .getFileName();
    fileName = new String(fileName.trim().getBytes(), "UTF-8"); //能解决部分中文问题
    System.out.println("filename=" + fileName);
    if (!fileName.equals("")) {
     String path = "g:/defggg/" + fileName;
     f.getFile(i).saveAs(path, SmartUpload.SAVE_PHYSICAL);
    }
   }
  } catch (Exception e) {
   e.printStackTrace();
   System.out.println("Unable to upload the file.");
   System.out.println("Error :" + e.toString());
  }
  response.sendRedirect("index.jsp");
}
}