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serialVersionUID in SessionBean

 
Joe Harry
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My session bean class when editing in eclipse, shows a yellow line and says that it does not declare a serialVersionUID of type long. Why do we need such a declaration for serializable classes?
 
krishna bulusu
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Please go through the below link for Serialization:
Serialization
But, I am not getting any such warning messages in eclipse for my session Beans. I am declaring the Beans using annotations.
 
Christophe Verré
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The Serialization API says it all. But if it really bothers you, you can turn the warning off in the Project Properties (Compiler options) in Eclipse.

API:

The serialization runtime associates with each serializable class a version number, called a serialVersionUID, which is used during deserialization to verify that the sender and receiver of a serialized object have loaded classes for that object that are compatible with respect to serialization. If the receiver has loaded a class for the object that has a different serialVersionUID than that of the corresponding sender's class, then deserialization will result in an InvalidClassException. A serializable class can declare its own serialVersionUID explicitly by declaring a field named "serialVersionUID" that must be static, final, and of type long:

ANY-ACCESS-MODIFIER static final long serialVersionUID = 42L;


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.
 
Joe Harry
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Thanks guys. Now I can relate why ecplise shows such a warning.
 
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