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Serialization - different JVM version ?

 
kri shan
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Source system serializes the object and attached serial version id send it to the destination system. But source system and destination system has different JVM version. Whether de-serialization will work at destination system ?
 
Campbell Ritchie
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Depends whether the class file has changed.
 
David Newton
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What happens when you try it?
 
kri shan
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Hi Campbell, If Class file has changed.
 
Ninad Kulkarni
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@ Kri shan

See this

Following is a quote from documentation

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. 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.


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
 
kri shan
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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.. How receiver validates serialVersionUID ?
 
David Newton
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It compares the serialVersionID of the incoming class with the one it loaded locally.
 
kri shan
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Dave wrote:It compares the serialVersionID of the incoming class with the one it loaded locally.
User is adding serialVersionID of the incoming class in the source system. My question is how it loaded locally on the destination system?
 
David Newton
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Because the class will have a serialVersionID there too. I'm not sure what the problem is... Serializable classes have a serialVersionID. The class being sent comes with a serialVersionID. The class definition on the receiving side will have its own serialVersionID. If they don't match, an exception is thrown. The receiving JVM loads the *local* class definition--it can't instantiate arbitrary classes, only classes which it can load. The values for the class's fields are deserialized (loaded) from the incoming class):
The Javadocs wrote:The defaultReadObject method uses information in the stream to assign the fields of the object saved in the stream with the correspondingly named fields in the current object. This handles the case when the class has evolved to add new fields.
 
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