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Java文件下载的几种方式

     public  HttpServletResponse download(String path, HttpServletResponse response) {
         try  {
             //  path是指欲下载的文件的路径。
            File file  =   new  File(path);
             //  取得文件名。
            String filename  =  file.getName();
             //  取得文件的后缀名。
            String ext  =  filename.substring(filename.lastIndexOf( " . " )  +   1 ).toUpperCase();

             //  以流的形式下载文件。
            InputStream fis  =   new  BufferedInputStream( new  FileInputStream(path));
             byte [] buffer  =   new   byte [fis.available()];
            fis.read(buffer);
            fis.close();
             //  清空response
            response.reset();
             //  设置response的Header
            response.addHeader( " Content-Disposition " ,  " attachment;filename= "   +   new  String(filename.getBytes()));
            response.addHeader( " Content-Length " ,  ""   +  file.length());
            OutputStream toClient  =   new  BufferedOutputStream(response.getOutputStream());
            response.setContentType( " application/octet-stream " );
            toClient.write(buffer);
            toClient.flush();
            toClient.close();
        }  catch  (IOException ex) {
            ex.printStackTrace();
        }
         return  response;
    }

     public   void  downloadLocal(HttpServletResponse response)  throws  FileNotFoundException {
         //  下载本地文件
        String fileName  =   " Operator.doc " .toString();  //  文件的默认保存名
         //  读到流中
        InputStream inStream  =   new  FileInputStream( " c:/Operator.doc " ); //  文件的存放路径
         //  设置输出的格式
        response.reset();
        response.setContentType( " bin " );
        response.addHeader( " Content-Disposition " ,  " attachment; filename=\ ""  + fileName +  " \ "" );
         //  循环取出流中的数据
         byte [] b  =   new   byte [ 100 ];
         int  len;
         try  {
             while  ((len  =  inStream.read(b))  >   0 )
                response.getOutputStream().write(b,  0 , len);
            inStream.close();
        }  catch  (IOException e) {
            e.printStackTrace();
        }
    }

     public   void  downloadNet(HttpServletResponse response)  throws  MalformedURLException {
         //  下载网络文件
         int  bytesum  =   0 ;
         int  byteread  =   0 ;

        URL url  =   new  URL( " windine.blogdriver.com/logo.gif " );

         try  {
            URLConnection conn  =  url.openConnection();
            InputStream inStream  =  conn.getInputStream();
            FileOutputStream fs  =   new  FileOutputStream( " c:/abc.gif " );

             byte [] buffer  =   new   byte [ 1204 ];
             int  length;
             while  ((byteread  =  inStream.read(buffer))  !=   - 1 ) {
                bytesum  +=  byteread;
                System.out.println(bytesum);
                fs.write(buffer,  0 , byteread);
            }
        }  catch  (FileNotFoundException e) {
            e.printStackTrace();
        }  catch  (IOException e) {
            e.printStackTrace();
        }
    }

//支持在线打开文件的一种方式

     public   void  downLoad(String filePath, HttpServletResponse response,  boolean  isOnLine)  throws  Exception {
        File f  =   new  File(filePath);
         if  ( ! f.exists()) {
            response.sendError( 404 ,  " File not found! " );
             return ;
        }
        BufferedInputStream br  =   new  BufferedInputStream( new  FileInputStream(f));
         byte [] buf  =   new   byte [ 1024 ];
         int  len  =   0 ;

        response.reset();  //  非常重要
         if  (isOnLine) {  //  在线打开方式
            URL u  =   new  URL( " file:/// "   +  filePath);
            response.setContentType(u.openConnection().getContentType());
            response.setHeader( " Content-Disposition " ,  " inline; filename= "   +  f.getName());
             //  文件名应该编码成UTF-8
        }  else  {  //  纯下载方式
            response.setContentType( " application/x-msdownload " );
            response.setHeader( " Content-Disposition " ,  " attachment; filename= "   +  f.getName());
        }
        OutputStream out  =  response.getOutputStream();
         while  ((len  =  br.read(buf))  >   0 )
            out.write(buf,  0 , len);
        br.close();
        out.close();
    }