ibatis里读取图片blob

<select id="getTxById" parameterClass="string" >
        select tx from txb where id=#id#
    </select>

public byte[]  getImage(String id){
            byte[] image = null;
            try {
                image = (byte[]) sqlMap.queryForObject("getTxById",id);
            } catch (SQLException e) {
                // TODO Auto-generated catch block
                e.printStackTrace();
            }
           
            return image;
    }