今天在看Jbpm的源代码中，发现其中的Hibernate中的PO的序列化对象基本上都有一个serialVersionUID的一个私有对象，就上网查找了一部分资料。
http://www.javapractices.com/Topic45.cjp
Guidelines for serialVersionUID : （serialVersionUID的指导纲要）
- 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(老练地) making changes to the class which will render(使..变成) 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