object byte array to object instance

[sam bartl]

We save object instance byte array into database , reload it into object instance . Suppose I have instance byte array in database and we modified object by adding a new property , old properties are as it is, now If I try to reload this byte array into modified object instance I get call cast exception is the any way I can reload the byte array into this modified object ?

[William Brogden]

IF what you are talking about is
1. serializing an object instance to a byte[] and saving it.
2. revising the class by adding a new variable (think variable, not property) (not modifying object, modifying class)
3. attempting to recover the serialized object using the new class definition.

THEN
No you can't, why would you expect to be able to?

See java.io.Serializable JavaDocs for the use of serialVersionUID

IF you are not talking about serializing an object, please explain more.

Bill

[sam bartl]

I am assuming this will work if my object delcares a serialVersionUID

private static final long serialVersionUID

please advice me what value should I give to this variable

[Rob Spoor]

Omit it at first, then use the "serialver" tool that you can find in the JDK's bin folder to generate one for you. If you use an IDE you can also let it generate it for you; it probably uses serialver in the background.

public class Test implements java.io.Serializable
{
}

I:\>serialver Test
Test:    static final long serialVersionUID = 2010307013874058143L;

I:\>

Then just copy and paste this declaration, and make it private.