JavaWeb -- 文件上传下载示例

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1. 上传简单示例

Jsp

<%@ page language="java" import="java.util.*"  pageEncoding="UTF-8"%><!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"><html><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>文件上传下载</title></head><body><form action="${pageContext.request.contextPath}/UploadServlet" enctype="multipart/form-data" method="post">上传用户：<input type="text" name="username" /> <br />上传文件1：<input type="file" name="file1" /> <br />上传文件2：<input type="file" name="file2" /> <br /><input type="submit" value="上传 "/></form> <br />${requestScope.message}</body></html>

Servlet

public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {try{//1.得到解析器工厂DiskFileItemFactory factory = new DiskFileItemFactory();//2.得到解析器ServletFileUpload upload = new ServletFileUpload(factory);//3.判断上传表单的类型if(!upload.isMultipartContent(request)){//上传表单为普通表单，则按照传统方式获取数据即可return;}//为上传表单，则调用解析器解析上传数据List<FileItem> list = upload.parseRequest(request);  //FileItem//遍历list，得到用于封装第一个上传输入项数据fileItem对象for(FileItem item : list){if(item.isFormField()){//得到的是普通输入项String name = item.getFieldName();  //得到输入项的名称String value = item.getString();System.out.println(name + "=" + value);}else{//得到上传输入项String filename = item.getName();  //得到上传文件名  C:\Documents and Settings\ThinkPad\桌面\1.txtfilename = filename.substring(filename.lastIndexOf("\\")+1);InputStream in = item.getInputStream();   //得到上传数据int len = 0;byte buffer[]= new byte[1024];//用于保存上传文件的目录应该禁止外界直接访问String savepath = this.getServletContext().getRealPath("/WEB-INF/upload");System.out.println(savepath);FileOutputStream out = new FileOutputStream(savepath + "/" + filename);  //向upload目录中写入文件while((len=in.read(buffer))>0){out.write(buffer, 0, len);}in.close();out.close();request.setAttribute("message", "上传成功");}}}catch (Exception e) {request.setAttribute("message", "上传失败");e.printStackTrace();}}

2. 修改后的上传功能：

注意事项：

1、上传文件名的中文乱码和上传数据的中文乱码upload.setHeaderEncoding("UTF-8");  //解决上传文件名的中文乱码//表单为文件上传，设置request编码无效,只能手工转换1.1 value = new String(value.getBytes("iso8859-1"),"UTF-8");1.2 String value = item.getString("UTF-8");2.为保证服务器安全，上传文件应该放在外界无法直接访问的目录3、为防止文件覆盖的现象发生，要为上传文件产生一个唯一的文件名4、为防止一个目录下面出现太多文件，要使用hash算法打散存储5.要限制上传文件的最大值，可以通过：ServletFileUpload.setFileSizeMax(1024)方法实现，并通过捕获：FileUploadBase.FileSizeLimitExceededException异常以给用户友好提示6.想确保临时文件被删除，一定要在处理完上传文件后，调用item.delete方法7.要限止上传文件的类型：在收到上传文件名时，判断后缀名是否合法8、监听文件上传进度：ServletFileUpload upload = new ServletFileUpload(factory);upload.setProgressListener(new ProgressListener(){public void update(long pBytesRead, long pContentLength, int arg2) {System.out.println("文件大小为：" + pContentLength + ",当前已处理：" + pBytesRead);}});9. 在web页面中动态添加文件上传输入项function addinput(){    var div = document.getElementById("file");        var input = document.createElement("input");    input.type="file";    input.name="filename";        var del = document.createElement("input");    del.type="button";    del.value="删除";    del.onclick = function d(){    this.parentNode.parentNode.removeChild(this.parentNode);    }            var innerdiv = document.createElement("div");            innerdiv.appendChild(input);    innerdiv.appendChild(del);        div.appendChild(innerdiv);    }

上传jsp:

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <title>My JSP 'upload2.jsp' starting page</title>        <script type="text/javascript">    function addinput(){    var div = document.getElementById("file");        var input = document.createElement("input");    input.type="file";    input.name="filename";        var del = document.createElement("input");    del.type="button";    del.value="删除";    del.onclick = function d(){    this.parentNode.parentNode.removeChild(this.parentNode);    }            var innerdiv = document.createElement("div");            innerdiv.appendChild(input);    innerdiv.appendChild(del);        div.appendChild(innerdiv);    }    </script>      </head>    <body>            <form action="" enctype="mutlipart/form-data"></form>    <table>    <tr>    <td>上传用户：</td>    <td><input type="text" name="username"></td>    </tr><tr>        <td>上传文件：</td>    <td>    <input type="button" value="添加上传文件" onclick="addinput()">     </td>     </tr>     <tr>     <td></td>    <td>    <div id="file">        </div>     </td>     </tr>         </table>          </body></html>

上传servlet

public class UploadServlet1 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {//request.getParameter("username");  //****错误request.setCharacterEncoding("UTF-8");  //表单为文件上传，设置request编码无效//得到上传文件的保存目录String savePath = this.getServletContext().getRealPath("/WEB-INF/upload");try{DiskFileItemFactory factory = new DiskFileItemFactory();factory.setRepository(new File(this.getServletContext().getRealPath("/WEB-INF/temp")));ServletFileUpload upload = new ServletFileUpload(factory);/*upload.setProgressListener(new ProgressListener(){public void update(long pBytesRead, long pContentLength, int arg2) {System.out.println("文件大小为：" + pContentLength + ",当前已处理：" + pBytesRead);}});*/upload.setHeaderEncoding("UTF-8");  //解决上传文件名的中文乱码if(!upload.isMultipartContent(request)){//按照传统方式获取数据return;}/*upload.setFileSizeMax(1024);upload.setSizeMax(1024*10);*/List<FileItem> list = upload.parseRequest(request);for(FileItem item : list){if(item.isFormField()){//fileitem中封装的是普通输入项的数据String name = item.getFieldName();String value = item.getString("UTF-8");//value = new String(value.getBytes("iso8859-1"),"UTF-8");System.out.println(name + "=" + value);}else{//fileitem中封装的是上传文件String filename = item.getName();  //不同的浏览器提交的文件是不一样  c:\a\b\1.txt   1.txtSystem.out.println(filename);if(filename==null || filename.trim().equals("")){continue;}filename = filename.substring(filename.lastIndexOf("\\")+1);InputStream in = item.getInputStream();String saveFilename = makeFileName(filename);  //得到文件保存的名称String realSavePath = makePath(saveFilename, savePath);  //得到文件的保存目录FileOutputStream out = new FileOutputStream(realSavePath + "\\" + saveFilename);byte buffer[] = new byte[1024];int len = 0;while((len=in.read(buffer))>0){out.write(buffer, 0, len);}in.close();out.close();item.delete();  //删除临时文件}}}catch (FileUploadBase.FileSizeLimitExceededException e) {e.printStackTrace();request.setAttribute("message", "文件超出最大值！！！");request.getRequestDispatcher("/message.jsp").forward(request, response);return;}catch (Exception e) {e.printStackTrace();}}public String makeFileName(String filename){  //2.jpgreturn UUID.randomUUID().toString() + "_" + filename;}public String makePath(String filename,String savePath){int hashcode = filename.hashCode();int dir1 = hashcode&0xf;  //0--15int dir2 = (hashcode&0xf0)>>4;  //0-15String dir = savePath + "\\" + dir1 + "\\" + dir2;  //upload\2\3  upload\3\5File file = new File(dir);if(!file.exists()){file.mkdirs();}return dir;}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

3. 下载功能

//列出网站所有下载文件public class ListFileServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String filepath = this.getServletContext().getRealPath("/WEB-INF/upload");Map map = new HashMap();listfile(new File(filepath),map);request.setAttribute("map", map);request.getRequestDispatcher("/listfile.jsp").forward(request, response);}public void listfile(File file,Map map){if(!file.isFile()){File files[] = file.listFiles();for(File f : files){listfile(f,map);}}else{String realname = file.getName().substring(file.getName().indexOf("_")+1);  //9349249849-88343-8344_阿_凡_达.avimap.put(file.getName(), realname);}}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

jsp显示

<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%><%@taglib prefix="c" uri="http://java.sun.com/jsp/jstl/core" %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"><html>  <head>    <title>My JSP 'listfile.jsp' starting page</title>  </head>    <body>    <c:forEach var="me" items="${map}">    <c:url value="/servlet/DownLoadServlet" var="downurl">    <c:param name="filename" value="${me.key}"></c:param>    </c:url>    ${me.value }  <a href="${downurl}">下载</a>  <br/>    </c:forEach>      </body></html>

下载处理servlet

public class DownLoadServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {String filename = request.getParameter("filename");  //23239283-92489-阿凡达.avifilename = new String(filename.getBytes("iso8859-1"),"UTF-8");String path = makePath(filename,this.getServletContext().getRealPath("/WEB-INF/upload"));File file = new File(path + "\\" + filename);if(!file.exists()){request.setAttribute("message", "您要下载的资源已被删除！！");request.getRequestDispatcher("/message.jsp").forward(request, response);return;}String realname = filename.substring(filename.indexOf("_")+1);response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(realname, "UTF-8"));FileInputStream in = new FileInputStream(path + "\\" + filename);OutputStream out = response.getOutputStream();byte buffer[] = new byte[1024];int len = 0;while((len=in.read(buffer))>0){out.write(buffer, 0, len);}in.close();out.close();}public String makePath(String filename,String savePath){int hashcode = filename.hashCode();int dir1 = hashcode&0xf;  //0--15int dir2 = (hashcode&0xf0)>>4;  //0-15String dir = savePath + "\\" + dir1 + "\\" + dir2;  //upload\2\3  upload\3\5File file = new File(dir);if(!file.exists()){file.mkdirs();}return dir;}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

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