今天在看Jbpm的源代碼中，發現其中的Hibernate中的PO的序列化對象基本上都有一個serialVersionUID的一個私有對象，就上網查找了一部分資料。
http://www.javapractices.com/Topic45.cjp
Guidelines for serialVersionUID : （serialVersionUID的指導綱要）
- always include it as a field, for example: "private static final long serialVersionUID = 7526472295622776147L; " include this field even in the first version of the class, as a reminder(提示) of its importance
- do not change the value of this field in future versions, unless you are knowingly(老練地) making changes to the class which will render(使..變成) it incompatible(不相容的) with old serialized objects
- new versions of Serializable classes may or may not be able to read old serialized objects; it depends upon the nature of the change; provide a pointer to Sun's guidelines for what constitutes a compatible(兼容地) change, as a convenience to future maintainers