serialVersionUID update

Posted on 2009-07-06
Last Modified: 2012-05-07
For serialized objects , if the serialVersionUID is not defined explicitly, by compile time java compiler creates a new one and this is compiler dependent.

We need to enforce that , if the update of object is incompatible with the new object, serialVersionUID must be set to a new value, otherwise it should remain unchanged. i.e If any attribute is deleted from the object serialVersionUID must be updated.

I am thinking to use externalize mechanism to serve the purpose . This is time consuming . But , is there any other way that makes the job easy and faster.
Question by:sukh54
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LVL 86

Accepted Solution

CEHJ earned 250 total points
ID: 24792199
You could use the checksum of the classfile as its serialVersionUID and check that they correspond

Author Comment

ID: 24792285
But , how we can check the checksum in the runtime ....and also is it flexible .. Will appreciate if you place some code snippet ...

Expert Comment

ID: 24792424
A good way would be to use an ANT (for example) task that generates the serialVersionUID according to some algorithm and injects the definition into the source.
Of course you'd have to work always on a copy of the source, and store in your version control system a version that only has a placeholder telling the task where to inject the actual value.

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LVL 86

Assisted Solution

CEHJ earned 250 total points
ID: 24792452

Author Comment

ID: 24792775
But , how about explicitly specifying the serialVersionUID in the serializable
classes?  .... the most worrying part is , I am wondering will it give any issue (InvalidClassExceptions) since the class defintions( with the added new filed serialVersionUID) may not match the corresponding serailized objects( which didnt have the field serialVersionUID) ...
         If the issue are there , how we can go about this
LVL 86

Assisted Solution

CEHJ earned 250 total points
ID: 24792817
You choose the UID - it's not a problem.

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