Does changing the class name affect Java Deserialization?

Question

I am making a modification and a separate application that allows replays to be saved for a certain game.

What I have to serialize and deserialize is an 2 arrays of class ContO, arrays of class Plane, Trackers, and a class Medium, and that is no problem.

To extend this functionality, I decide to reconstruct it in the separate application so that it supports 2 versions of said game. The way I plan to do this is to use abstract classes named Medium, ContO, Plane, and Trackers, and the classes that will extend those will be named things like MediumVersion1 and MediumVersion2, ContOVersion1, and so on.

In the original game files the class is named ContO, Plane, Trackers, and Medium for both versions, and what I wonder is: by changing the name of the class to reflect the version of the file that will be deserialized, will it effect the deserialization process?

For example, I serialize the class as the name of ContO in the original game files, but deserialize it under a new class name named ContOVersion1, but contains the exact same variables.

I believe so. What happened when you tried it? – Elliott Frisch May 24 '15 at 21:47 — Elliott Frisch, May 24 '15 at 21:47
How do you propose to do this? – Stephen C May 24 '15 at 21:47 — Stephen C, May 24 '15 at 21:47

bhspencer · Accepted Answer · 2015-05-25T00:02:49.447

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I just tried this and the answer is you cannot change the class name. You will end up with a ClassCastException when you try to cast the object you get back from ObjectInputStream.readObject() into your new class with a different name. This is the case even if you keep the same serialVersionUID on both classes.

edited May 25 '15 at 00:02

answered May 24 '15 at 22:18

bhspencer

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Yea, I also realized that it can't be done when i saw the java docs for ObjectOutputStream.writeObject() - http://prntscr.com/7991g7, as the name is indeed written in the serialization process – user2741371 May 25 '15 at 16:44

user207421 · Answer 2 · 2015-05-24T23:42:01.587

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You can definitely not do this.

The original class and package names are encoded along with the data, and the incoming object is constructed as that class, so, to avoid a class cast exception, what you cast it to must be identical, as must many other aspects of the class - but not all of them. See the Object Versioning chapter of the Object Serialization Specification for more information.

edited May 24 '15 at 23:42

answered May 24 '15 at 23:08

user207421

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Link for directing me to the Object Serialization Specification thing? – user2741371 May 25 '15 at 16:46
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Java Object Serialization Specification. 5 seconds in Google. – user207421 May 26 '15 at 03:25

Does changing the class name affect Java Deserialization?

2 Answers2