java中的可序列化工作原理如何？

Question

If I have an instance of a class that I store in a session I need to make it serializable. This class has a static variable, will this be serialized in every instance stored?

The static variable is a reference to a cache containing a lot of data in the background. Will all of this data be serialized? If so, it seems preferable to make this variable transient and re-fetch the cache instance each time the instance is restored. Maybe not store the cache instance at all in the class.

Will the constructor execute when a class is restored from a serialized state? if not is there any other method I can use to re-instate a transient variable?

Answer 1

This class has a static variable, will this be serialized in every instance stored?

No. According to the Java Object Serialization Specificaiton : "Default serializable fields of a class are defined to be the non-transient and non-static fields."

Will the constructor execute when a class is restored from a serialized state?

No. Deserialization bypasses constructors (unless you have a non-serializable superclass).

if not is there any other method I can use to re-instate a transient variable?

You can use the readObject() method for that, as described in the Serializable API doc.

Answer 2

static and transient fields are not serialized. No, the constructor is not called. For more details, please check this out: http://java.sun.com/developer/technicalArticles/ALT/serialization/