javaWeb 实现上传+下载文件

上传下载在web项目中应该是很常见的需求，能够熟练敲出代码实现是web开发人员必不可少的

下面简化的上传：

jsp页面的实现：

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core"  prefix = "c" %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head><title>My JSP 'uploadfile.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"><!--<link rel="stylesheet" type="text/css" href="styles.css">--></head><body><form action="<c:url value = '/UploadServlet1' />" method="post" enctype="multipart/form-data" >用户名：<input type = "text" name = "username">上传照片：<input type = "file" name = "photo"><input type = "submit" value="提交"></form></body>
</html>

servlet的实现:

package cn.Lionel.servlet;import java.io.File;
import java.io.IOException;
import java.util.List;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;public class UploadServlet1 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html");//创建工厂DiskFileItemFactory factory = new DiskFileItemFactory() ;//通过工厂创建解析器ServletFileUpload upload = new ServletFileUpload(factory);try {List<FileItem> list = upload.parseRequest(request);FileItem item1 = list.get(0);FileItem item2 = list.get(1);System.out.println("普通表单项："+item1.getName()+"="+item1.getString("utf-8"));System.out.println("文件表单项:");System.out.println("Content-Type"+item2.getContentType());System.out.println("filename="+item2.getName());System.out.println("size = "+item2.getSize());item2.write(new File("d:\\1.jpg"));} catch (Exception e) {throw new RuntimeException() ;}}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

下面是设置了缓存文件夹+文件打散

jsp页面跟上面差不多：

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%>
<%@ taglib uri = "http://java.sun.com/jsp/jstl/core"  prefix = "c" %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html><head><title>My JSP 'uploadfile.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"><!--<link rel="stylesheet" type="text/css" href="styles.css">--></head><body><h1>${msg }</h1><form action="<c:url value = '/UploadServlet2' />" method="post" enctype="multipart/form-data" >用户名：<input type = "text" name = "username">上传照片：<input type = "file" name = "photo"><input type = "submit" value="提交"></form></body>
</html>

servlet的实现依赖commons.fileupload组件

package cn.Lionel.servlet;import java.io.File;
import java.io.IOException;
import java.util.List;
import java.util.UUID;import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.apache.commons.fileupload.FileItem;
import org.apache.commons.fileupload.FileUploadBase;
import org.apache.commons.fileupload.FileUploadException;
import org.apache.commons.fileupload.disk.DiskFileItemFactory;
import org.apache.commons.fileupload.servlet.ServletFileUpload;public class UploadServlet3 extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html");//设置缓冲区和临时目录DiskFileItemFactory factory = new DiskFileItemFactory(100,new File("e:\\temp"));ServletFileUpload upload = new ServletFileUpload(factory);//限制上传的文件大小//upload.setFileSizeMax(200*1024) ;//限制整个表单的大小：upload.setSizeMax();try {List<FileItem> list = upload.parseRequest(request);FileItem item = list.get(1);String filename = item.getName();//处理有些浏览器返回的文件名是绝对路径int index = filename.lastIndexOf("\\") ;if(index != -1){filename = filename.substring(index+1);}int hashCode = filename.hashCode();//把hash值转换为十六进制String hex = Integer.toHexString(hashCode);String realPath = this.getServletContext().getRealPath("WEB-INF/files");File dirFile = new File(realPath + "/" + hex.charAt(0) + "/"+ hex.charAt(1));//创建目录链dirFile.mkdirs();String savename = uuid()+"_"+filename;File destFile = new File(dirFile,savename);item.write(destFile);}catch (FileUploadException e) {if(e instanceof FileUploadBase.FileSizeLimitExceededException){request.setAttribute("msg", "您上传的文件超出200KiB!") ;request.getRequestDispatcher("/uploadfile2.jsp").forward(request, response) ;return ;}} catch (Exception e) {throw new RuntimeException();}}private String uuid() {return UUID.randomUUID().toString().replace("-", "").toUpperCase();}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}}

说完了上传，该说下载了：

该事先依赖commons.io组件，直接访问servlet实现下载。要下载的文件需要改你自己项目中存在的文件。

package cn.Lionel.servlet;import java.io.FileInputStream;
import java.io.IOException;
import java.net.URLEncoder;import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;import org.apache.commons.io.IOUtils;import sun.misc.BASE64Encoder;public class DownloadServlet extends HttpServlet {public void doGet(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {response.setContentType("text/html;charset = utf-8");String filename = "E:\\KuGou\\可米小子 - 青春纪念册.mp3"; //改为自己项目中存在的文件//这种方法对部分字符仍存在乱码！//String dname = new String("青春纪念册.mp3".getBytes("utf-8"), "iso-8859-1");//这种方法最常用！解决文件名乱码String dname = filenameEncoding("青春纪念册.mp3",request);String contentType = this.getServletContext().getMimeType(filename);String contentDisposition = "attachment;filename="+dname;response.setHeader("Content-Type", contentType + "");response.setHeader("Content-Disposition", contentDisposition);FileInputStream input = new FileInputStream(filename);ServletOutputStream out = response.getOutputStream();IOUtils.copy(input, out);input.close();}public void doPost(HttpServletRequest request, HttpServletResponse response)throws ServletException, IOException {doGet(request, response);}public static String filenameEncoding(String filename, HttpServletRequest request) throws IOException {String agent = request.getHeader("User-Agent"); //获取浏览器if (agent.contains("Firefox")) {BASE64Encoder base64Encoder = new BASE64Encoder();filename = "=?utf-8?B?"+ base64Encoder.encode(filename.getBytes("utf-8"))+ "?=";} else if(agent.contains("MSIE")) {filename = URLEncoder.encode(filename, "utf-8");} else {filename = URLEncoder.encode(filename, "utf-8");}return filename;}
}

能力有限。写博客只为了防止自己忘记，方便查找，如有错误，还望指出

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