Sudhanshu S.

Serialization is a mechanism in java where an object can be represented as a sequence of bytes that includes the object's data as well as information about the object's type. Once an object is serialized its written to a file which can later be again deserialized to recreate the object in the memory. Consider a distributed hosting platform where web application is deployed across multiple servers. Each server has its own JVM container and they need to share common data (for ex - session object data), to serve the incoming requests. This objective is achieved using serialization. Each serialized class is associated with a version number, called a serialVersionUID which is used during deserialization to verify that the receiver has loaded the very class that the sender had intended. In case the receiver has loaded a class with different serialVersionUID, than that of corresponding sender class, then it'll result in InvalidClassCastException. If no serialVersionUID has been assigned, a default value gets assigned by the compiler. However, as a best practice, it is strongly recommended that all serializable classes explicitly declare serialVersionUID since the default serialVersionUID computation is highly sensitive and may also vary across various java compiler implementations.