Java中2个不同JVM上类的对象的序列化

Question

I have a class say Counter. I serialize Object of this class on JVM-1 in one machine & transfer the serialized Object as a network stream to another machine & deserialize there in JVM-2. Will this Object get deserialized properly ? Would there be any error/exception thrown in this case? Assuming i have compiled the class on both JVMs. I am assuming that there is no serial Version UID present in the classes

Answer 1

只要两端都运行相同的代码/ jdk（尽管可以使用不同的jdk），则序列化/反序列化将不是问题。

Answer 2

if you have serialVersionUID in your class, serialize/deserialize will not be a problem, but if serialVersionUID is missing in your code, as you are compiling class with both JVM(I understand, .class file has same content but compiled with different JVMs) in that case, serialVersionUID is assigned by java, which won't be same, hence serialize/deserialize will not work. So, add

private static final long serialVersionUID = -6903933977591709194L;

in case you haven't added, with any value, and compile as many times, rest assured, serialize/deserialize will work. :)

Answer 3

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 = 11L;

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