Java Serialization - Java.Io.Invalidclassexception Local Class Incompatible

java.io.InvalidClassException: local class incompatible:

If a class does not explicitly define a private static final long serialVersionUID in the code it will be autogenerated, and there is no guarantee that different machines will generate the same id; it looks like that is exactly what happened.
Also if the classes are different in any way (using different versions of the class) the autogenerated serialVersionUIDs will also be different.

From the Serializable interface's docs:

If a serializable class does not explicitly declare a serialVersionUID, then the serialization runtime will calculate a default serialVersionUID value for that class based on various aspects of the class, as described in the Java(TM) Object Serialization Specification. However, it is strongly recommended that all serializable classes explicitly declare serialVersionUID values, since the default serialVersionUID computation is highly sensitive to class details that may vary depending on compiler implementations, and can thus result in unexpected InvalidClassExceptions during deserialization. Therefore, to guarantee a consistent serialVersionUID value across different java compiler implementations, a serializable class must declare an explicit serialVersionUID value. It is also strongly advised that explicit serialVersionUID declarations use the private modifier where possible, since such declarations apply only to the immediately declaring class--serialVersionUID fields are not useful as inherited members. Array classes cannot declare an explicit serialVersionUID, so they always have the default computed value, but the requirement for matching serialVersionUID values is waived for array classes.

You should define a serialVersionUID in the class definition, e.g.:

class MyClass implements Serializable {
    private static final long serialVersionUID = 6529685098267757690L;
    ...

how resolve java.io.InvalidClassException: local class incompatible: stream classdesc serialVersionUID

Define a member in the class concerned:

private static final long serialVersionUID = 1113799434508676095L;

This solves the problem described in the message, by forcing the serialVersionUID of the local class to match what was put in the stream when you serialized the old version of the class, which would have been computed automatically over various class attributes if no serialVersionUUD field was present at that time.

It is possible that you altered the class in an incompatible way, which will then produce a different exception. See the Object Serialization Specification chapter on Versioning for details. However merely adding or removing a field doesn't have that effect.

Java serialization - java.io.InvalidClassException local class incompatible

@DanielChapman gives a good explanation of serialVersionUID, but no solution. the solution is this: run the serialver program on all your old classes. put these serialVersionUID values in your current versions of the classes. as long as the current classes are serial compatible with the old versions, you should be fine. (note for future code: you should always have a serialVersionUID on all Serializable classes)

if the new versions are not serial compatible, then you need to do some magic with a custom readObject implementation (you would only need a custom writeObject if you were trying to write new class data which would be compatible with old code). generally speaking adding or removing class fields does not make a class serial incompatible. changing the type of existing fields usually will.

Of course, even if the new class is serial compatible, you may still want a custom readObject implementation. you may want this if you want to fill in any new fields which are missing from data saved from old versions of the class (e.g. you have a new List field which you want to initialize to an empty list when loading old class data).

Java - InvalidClassException local class incompatible serialVersionUID

The serialVersionUID needs to be defined with the same value as in the stream: -5756298698047880134.

You must have deployed two different versions of the JDOM library.

---

Related Topics