如何使扩展非序列化的Java类可序列化

Question

MyClass1 extends MyClass2 implements Serializable

I am trying to use saveOnInstanceState in my android app on a HashMap by using

 savedInstanceState.getSerializable()

I have does this with other hashmaps that that use custom classes but by making those classes Serializable however I seem to be getting errors with this even after I made this serializable because MyClass2 is not serializable. MyClass2 is a third party library and hence I cannot modify it and make it serializable, is there anything I can do?

Thank you!

Answer 1

You cannot generally do this, as Jan's answer states. Under some circumstances there are work arounds that will make it happen, but they are a bit brittle even when they work. To have a chance at this, you'll need the following to apply:

• You have sufficient insight into the super class structure to know what data is necessary to capture its current state.
• You need to have access (either through public or protected member variables or through something like getters) to the data necessary to capture its current state.
• You need to have access (either through public or protected member variables or through something like setters) to change the data fields necessary to reconstitute its current state.
• You need to use either the serialPersistentFields approach or a carefully constructed writeObject / readObject pair of implementations that save / read the data from the super class during serialization and deserialization. This will necessarily require the knowledge of and access to the super class structure described in the earlier bullets.
• The super class must have a no-arg constructor. (This won't matter for serializing, but you'll need it when you de-serialize.)

Of course in doing all of this, you're going to use some knowledge of the super class, which means if the super class implementation changes, this may break in hard-to-find ways.

Answer 2

Unfortunately you can't. If you could do this, it would be a security flaw, as you could serialize every class, even if the class was not supposed to.