mysql 图片数据的写入

Connection cnn =null;PreparedStatement pst=null;ResultSet rs =null;InputStream frd=null;try {cnn= jdbcUtils.getConnection();String sql = " insert into test2 (t) values(?) ";String path = demo1.class.getClassLoader().getResource("x.png").getPath();pst = cnn.prepareStatement(sql);try {File file = new File(path);frd = new FileInputStream(file);pst.setBinaryStream(1,frd,(int)file.length());/*去掉 强制转换的 (int) 程序就出错， 不知道是怎么一回事*/} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();}int num = pst.executeUpdate();if (num>0){System.out.println("插入数据成功!~");}} catch (SQLException e) {e.printStackTrace();}pst.setBinaryStream(1,frd,(int)file.length());

上句如果去掉强制转换时则运行出错， 不知道为什么