/**  
     * 从数据库下载数据  
     * @param filename  
     * @return int 0代表下在失败，1代表下载成功  
     */  
    public int downBlob(String filename){   
        BLOB blob=null;   
        String sql="SELECT file_ FROM blobtest WHERE filename=?";   
        //设立一个标志位，来监控整个运行流程   
        int result=0;   
        try {   
            conn.setAutoCommit(true);   
            pstm=conn.prepareStatement(sql);   
            pstm.setString(1, filename);   
            rst=pstm.executeQuery();   
            while(rst.next()){   
                blob=(BLOB)rst.getBlob(1);   
                result=1;   
            }   
            InputStream in=blob.getBinaryStream();   
            File file=new File("c:\\download_mj\\"+filename);   
            OutputStream out=new FileOutputStream(file);   
            byte[] buffer=new byte[1024*8];   
            int length=0;   
            //刚开始忘了加length结果读的是空的，还让我郁闷了很长时间，太粗心了还是。。。   
            while((length=in.read(buffer, 0, 1024*7))!=-1){   
                result=1;   
                out.write(buffer, 0, length);   
                out.flush();   
            }   
            pstm.close();   
            out.close();   
            in.close();   
               
        } catch (SQLException e) {   
            result=0;   
            e.printStackTrace();   
        } catch (FileNotFoundException e) {   
            result=0;   
            e.printStackTrace();   
        } catch (IOException e) {   
            result=0;   
            e.printStackTrace();   
        }   
        return result;   
    }