即使类已序列化,blob对象也无法正常工作

我有一个类,它是序列化的,它将大量的数据对象转换成blob保存到数据库中。在同一个类中,有decode方法将blob转换成实际的对象。下面是对象的编码和解码代码。

private byte[] encode(ScheduledReport schedSTDReport)
{
    byte[] bytes = null;
    try
    {
        ByteArrayOutputStream bos = new ByteArrayOutputStream(); 
        ObjectOutputStream oos = new ObjectOutputStream(bos);
        oos.writeObject(schedSTDReport);
        oos.flush(); 
        oos.close(); 
        bos.close();
        //byte [] data = bos.toByteArray();
        //ByteArrayOutputStream baos = new ByteArrayOutputStream();
        //GZIPOutputStream out = new GZIPOutputStream(baos);
        //XMLEncoder encoder = new XMLEncoder(out);
        //encoder.writeObject(schedSTDReport);
        //encoder.close();
        bytes = bos.toByteArray();
        //GZIPOutputStream out = new GZIPOutputStream(bos);
        //out.write(bytes);
        //bytes = bos.toByteArray();

    }
    catch (Exception e)
    {
        _log.error("Exception caught while encoding/zipping Scheduled STDReport", e);
    }
    decode(bytes);
    return bytes;
}


/*
 * Decode the report definition blob back to the
 * ScheduledReport object.
 */
private ScheduledReport decode(byte[] bytes)
{
    ByteArrayInputStream bais = new ByteArrayInputStream(bytes);
    ScheduledReport sSTDR = null;
    try
    {
        ObjectInputStream ois = new ObjectInputStream(bais);

        //GZIPInputStream in = new GZIPInputStream(bais);
        //XMLDecoder decoder = new XMLDecoder(in);
        sSTDR = (ScheduledReport)ois.readObject();//decoder.readObject();
        //decoder.close();
    }
    catch (Exception e)
    {
        _log.error("IOException caught while decoding/unzipping Scheduled STDReport", e);
    }
    return sSTDR;
}

这里的问题是当我在这个班上换了别的东西 意味着任何其他方法,都会创建一个新的类版本,因此该类的新版本无法解码最初编码的blob对象。我要传递给encode的对象也是seralized对象,但这个问题存在。有什么想法吗谢谢