commons-fileupload实现文件上传下载

时间：2020-12-03 20:59:54

commons-fileupload是Apache提供的一个实现文件上传下载的简单，有效途径,需要commons-io包的支持，本文是一个简单的示例

上传页面,注意设置响应头

<body>
<center>
<h1>文件上传页面</h1><hr>
<form action="${pageContext.request.contextPath }/servlet/UploadServlet" method="post" enctype="multipart/form-data">
    选择文件：<input type="file" name="file1"/><br>
    描述信息:<textarea rows="5" cols="45" name="discription"></textarea><br>
<input type="submit" value="上传"/>
</form>
</center>
</body>

上传的servlet

//上传文件
        String upload=this.getServletContext().getRealPath("WEB-INF/upload");

        String temp=this.getServletContext().getRealPath("WEB-INF/temp");

        Map pmap=new HashMap();
        //get client IP address
        pmap.put("ip", request.getRemoteAddr());

        DiskFileItemFactory factory=new DiskFileItemFactory();
        //设定内存缓冲区大小 Set the memory buffer size
        factory.setSizeThreshold(1024*100);
        //指定临时文件目录 Specifies the directory for temporary files
        factory.setRepository(new File(temp));


        ServletFileUpload fileUpload=new ServletFileUpload(factory);
        fileUpload.setHeaderEncoding("utf-8");
        fileUpload.setFileSizeMax(1024*1024*100);
        fileUpload.setSizeMax(1024*1024*200);

        //set form style enctype="multipart/form-data"
        if(!fileUpload.isMultipartContent(request))
        {
            throw new RuntimeException("请使用正确的表单进行上传");
        }

        //解析request
        try {
            List<FileItem> list= fileUpload.parseRequest(request);

            //遍历list
            for(FileItem item:list)
            {
                if(item.isFormField())
                {
                    String name=item.getFieldName();
                    String value=item.getString("utf-8");

                    pmap.put(name, value);
                }else
                {
                    String realname=item.getName();
                    String arry[]=realname.split("\\\\");
                    realname=arry[arry.length-1];
                    System.out.println(realname);
                    String uuidName=UUID.randomUUID().toString()+"_"+realname;

                    pmap.put("realname", realname);
                    pmap.put("uuidname", uuidName);

                    InputStream in=item.getInputStream();
                    String hash=Integer.toHexString(uuidName.hashCode());
                    String savepath="/WEB-INF/upload";
                    for(char c:hash.toCharArray())
                    {
                        upload+="/"+c;
                        savepath+="/"+c;
                    }
                    new File(upload).mkdirs();
                    pmap.put("savepath", savepath);
                    OutputStream out=new FileOutputStream(new File(upload,uuidName));
                    IOUtils.In2Out(in, out);
                    IOUtils.close(in, out);

                    item.delete();
                }
            }

        } catch (Exception e) {
            // TODO 自动生成的 catch 块
            e.printStackTrace();
        }

        //向数据库中插入数据

        Resourse r=new Resourse(); 
        try {
            BeanUtils.populate(r, pmap);
            String sql="insert into netdisk values(null,?,?,?,?,null,?)";
            QueryRunner runner=new QueryRunner(DaoUtils.getSource());
            runner.update(sql,r.getUuidname(),r.getRealname(),r.getSavepath(),r.getIp(),r.getDescription());
        } catch (Exception e) {
            // TODO 自动生成的 catch 块
            e.printStackTrace();
        } 

        //重定向回主页
        response.sendRedirect(request.getContextPath()+"/index.jsp");

为防止重名，所以使用了UUIDNAME,把文件上传到web-inf/upload文件夹下，并且将路径与文件名保存到数据库中，上传功能完成

下载实现

下载页面

<body>
<center>
<h1>下载列表</h1><hr>
<c:forEach items="${requestScope.list }" var="r">
<h2>文件名:${r.realname }<br></h2>
        上传时间:${r.uploadtime }<br>
        上传者IP：${r.ip }<br>
        描述信息：${r.description }<br>
<a href="${pageContext.request.contextPath }/servlet/DownServlet?id=${r.id}">下载</a><br><hr>
</c:forEach>
</center>
</body>

下载实现

  response.setContentType("text/html;charset=utf-8");
          //获取ID
        String id=request.getParameter("id");
        //根据ID查找资源
        String sql="select * from netdisk where id=?";
        Resourse r=null;
        QueryRunner runner=new QueryRunner(DaoUtils.getSource());
        try {
             r= runner.query(sql, new BeanHandler<Resourse>(Resourse.class), id);
        } catch (SQLException e) {
            // TODO 自动生成的 catch 块
            e.printStackTrace();
        }

        if(r==null)
        {
            response.getWriter().write("找不到该资源!!!!");
            return;
        }else
        {
            //指定响应头
            response.setHeader("Content-Disposition", "attachment;filename="+URLEncoder.encode(r.getRealname(),"UTF-8"));
            response.setContentType(this.getServletContext().getMimeType(r.getRealname()));
            String filePath=this.getServletContext().getRealPath(r.getSavepath()+"/"+r.getUuidname());
            InputStream in=new FileInputStream(filePath);
            OutputStream out=response.getOutputStream();
            IOUtils.In2Out(in, out);
            IOUtils.close(in, null);
        }

上传下载完成，注意，下载时一定要指定两个响应头

IO工具类

public class IOUtils {
private IOUtils() {
    }

public static void In2Out(InputStream in,OutputStream out) throws IOException{
byte [] bs = new byte[1024];
int i = 0;
while((i=in.read(bs))!=-1){
out.write(bs,0,i);
        }
    }

public static void close(InputStream in,OutputStream out){
if(in!=null){
try {
in.close();
            } catch (IOException e) {
                e.printStackTrace();
            }finally{
in = null;
            }
        }
if(out!=null){
try {
out.close();
            } catch (IOException e) {
                e.printStackTrace();
            }finally{
out = null;
            }
        }
    }
}

完成

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