Explain Serialization mechanism ?

Java’s object serialization allows you to take any object that implements the Serializable interface and turn it into a sequence of bytes that can later be fully restored to regenerate the original object. This is even true across a network, which means that the serialization mechanism automatically compensates for differences in operating systems. That is, you can create an object on a Windows machine, serialize it, and send it across the network to a Unix machine, where it will be correctly reconstructed. You don’t have to worry about the data representations on the different machines, the byte ordering, or any other details.
By itself, object serialization is interesting because it allows you to implement lightweight persistence. Remember that persistence means that an object’s lifetime is not determined by whether a program is executing; the object lives in between invocations of the program. By taking a serializable object and writing it to disk, then restoring that object when the program is reinvoked, you’re able to produce the effect of persistence. The reason it’s called “lightweight” is that you can’t simply define an object using some kind of “persistent” keyword and let the system take care of the details (although this might happen in the future). Instead, you must explicitly serialize and deserialize the objects in your program. If you need a more serious persistence mechanism, consider Java Data Objects (JDO) or a tool like Hibernate (http://hibernate.sourceforge.net). Object serialization was added to the language to support two major features. Java’s Remote Method Invocation (RMI) allows objects that live on other machines to behave as if they live on your machine. When sending messages to remote objects, object serialization is necessary to transport the arguments and return values. RMI is discussed in Thinking in Enterprise Java.
Object serialization is also necessary for JavaBeans.