javaweb基于spring MVC的上传下载实例(下)

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文件下载

　　要将Web应用系统中的文件资源提供给用户进行下载，首先我们要有一个页面列出上传文件目录下的所有文件，当用户点击文件下载超链接时就进行下载操作，编写一个ListFileServlet，用于列出Web应用系统中所有下载文件。

1.1 搭建前台页面
download.html代码如下:

<!DOCTYPE HTML><html><head> <title>下载文件显示页面</title></head> <body>    <div id="fileName"></div></body></html>

对download.html添加js:

<script ><!-- 初始化加载download()函数 -->$(function(){    download();}); function download(){   $.ajax({     url: 'cloud/load/download',      type: 'POST',        dataType:'JSON',     cache: false,       processData: false,       contentType: false,     success : function(date){       var file="";       $.each(date,function(key,values){         var newKey = "/D:/Download/"+key;         file += "<div>"+key+"&nbsp;&nbsp;"+"<a href='cloud/load/downloadFile?fileName="+key+"'>"+"下载"+"</a>"+"</div>"+"<br>";         $(values).each(function(){           file+="\t"+this;          });        });       alert("success");       },        error : function(e){        alert("error");      }      });  }</script>

说明:
在spring mvc框架下,通过spring注解,这里的ajax的url指向的是UploadAndDownloadController的download()方法

1.2 controller
UploadAndDownloadController.Java代码如下:

 package com.cloud.web.controller;import java.io.IOException;import java.util.HashMap;import java.util.Map;import javax.annotation.Resource;import javax.servlet.ServletException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.stereotype.Controller;import org.springframework.ui.ModelMap;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RequestMethod;import org.springframework.web.bind.annotation.RequestParam;import org.springframework.web.bind.annotation.ResponseBody;import org.springframework.web.multipart.MultipartFile;import com.cloud.web.service.FileLoadService;@Controller@RequestMapping("/load")public class UploadAndDownloadController {    @Resource    public FileLoadService fileLoadService;    /**     * 显示要下载的文件     * @param request     * @param response     * @param model     * @return     * @throws ServletException     * @throws IOException     */    @RequestMapping(value = "/download", method = RequestMethod.POST)    @ResponseBody    public Map<String,String> download(HttpServletRequest request, HttpServletResponse response,  ModelMap model) throws ServletException,  IOException{      Map<String,String> map = fileLoadService.doGet(request, response);      return map;    }    /**     * 文件下载到本地     * @param request     * @param response     * @param model     * @throws ServletException     * @throws IOException     */    @RequestMapping(value = "/downloadFile", method = RequestMethod.GET)    @ResponseBody    public void downloadFile(HttpServletRequest request, HttpServletResponse response,  ModelMap model) throws ServletException,  IOException{      String filename =request.getParameter("fileName");      fileLoadService.doGetFile(request, response ,filename);    }}

1.3 service接口
FileLoadService程序如下:

package com.cloud.web.service;import java.io.File;import java.io.IOException;import java.util.Map;import javax.servlet.ServletException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;public interface FileLoadService {    Map<String,String> doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException;    void listfile(File file,Map<String,String> map);    void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException;    void  doGetFile(HttpServletRequest request, HttpServletResponse response,String filename) throws ServletException, IOException;}

1.4 service的实现类
FileLoadServiceImpl.java程序如下:

package com.cloud.web.service.impl;import java.io.BufferedInputStream;import java.io.BufferedOutputStream;import java.io.File;import java.io.FileInputStream;import java.io.IOException;import java.io.InputStream;import java.io.OutputStream;import java.net.URLEncoder;import java.util.HashMap;import java.util.Map;import javax.servlet.ServletException;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import org.springframework.stereotype.Service;import com.cloud.web.service.FileLoadService;@Servicepublic class FileLoadServiceImpl implements FileLoadService{    /**     * 待下载文件的显示     */    @Override    public Map<String,String> doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException{        //获取上传文件的目录        String uploadFilePath = "/D:/Download/";        //存储要下载的文件名        Map<String,String> fileNameMap = new HashMap<String,String>();        //递归遍历uploadFilePath目录下的所有文件和目录，将文件的文件名存储到map集合中        listfile(new File(uploadFilePath),fileNameMap);//File既可以代表一个文件也可以代表一个目录        //将Map集合返回页面        return fileNameMap;    }         public void listfile(File file,Map<String,String> map){        //如果file代表的不是一个文件，而是一个目录        if(!file.isFile()){        //列出该目录下的所有文件和目录        File files[] = file.listFiles();        //遍历files[]数组        for(File f : files){        //递归         listfile(f,map);         }    }else{            String realName = file.getName().substring(file.getName().indexOf("_")+1);            //file.getName()得到的是文件的原始名称，这个名称是唯一的，因此可以作为key，realName是处理过后的名称，有可能会重复            map.put(file.getName(), realName);        }    }    public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {        doGet(request, response);    }        /**         * 将显示的文件下载到本地         */        @Override        public void doGetFile(HttpServletRequest request, HttpServletResponse response,String filename) throws ServletException,IOException {            //得到要下载的文件名             String fileName = filename;             //解决乱码问题             fileName = new String(fileName.getBytes("iso8859-1"),"UTF-8");             String fileSaveRootPath="/D:/Download";             //文件路径             File file = new File(fileSaveRootPath + "/" + fileName);             //如果文件不存在             if(!file.exists()){                 request.setAttribute("message", "您要下载的资源已被删除！！");                 return;             }            //处理文件名            String realname = fileName.substring(fileName.indexOf("_")+1);            //设置响应头，控制浏览器下载该文件            response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(realname, "UTF-8"));            InputStream fis = new BufferedInputStream(new FileInputStream(fileSaveRootPath + "\\" + fileName));            byte[] buffer = new byte[fis.available()];             fis.read(buffer);  //读取文件流            fis.close();//关闭文件流            response.reset();//重置结果集            response.setHeader("content-disposition", "attachment;filename=" + URLEncoder.encode(realname, "UTF-8"));            response.addHeader("Content-Length", "" + file.length());  //返回头 文件大小            response.setContentType("application/octet-stream");    //设置数据种类            ///获取返回体输出权            OutputStream os = new BufferedOutputStream(response.getOutputStream());              os.write(buffer); // 输出文件            os.flush();            os.close();        }          public void doPostFile(HttpServletRequest request, HttpServletResponse response,String filename)throws ServletException, IOException {               doGetFile(request, response,filename);           }}

以上文件下载完成~

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