What is object serialization?

Question

What is meant by \"object serialization\"? Can you please explain it with some examples?

Answer 1

|*| Serializing a class : Converting an object to bytes and bytes back to object (Deserialization).

class NamCls implements Serializable
{
    int NumVar;
    String NamVar;
}

|=> Object-Serialization is process of converting the state of an object into steam of bytes.

• |-> Implement when you want the object to exist beyond the lifetime of the JVM.
  
• |-> Serialized Object can be stored in Database.
  
• |-> Serializable-objects cannot be read and understood by humans so we can acheive security.
  

|=> Object-Deserialization is the process of getting the state of an object and store it into an object(java.lang.Object).

• |-> Before storing its state it checks whether serialVersionUID form input-file/network and .class file serialVersionUID are same.
    If not throw java.io.InvalidClassException.
  

|=> A Java object is only serializable, if its class or any of its superclasses

• implements either the java.io.Serializable interface or
  
• its subinterface, java.io.Externalizable.
  

|=> Static fields in a class cannot be serialized.

class NamCls implements Serializable
{
    int NumVar;
    static String NamVar = "I won't be serializable";;
}

|=> If you do not want to serialise a variable of a class use transient keyword

class NamCls implements Serializable
{
    int NumVar;
    transient String NamVar;
}

|=> If a class implements serializable then all its sub classes will also be serializable.

|=> If a class has a reference of another class, all the references must be Serializable otherwise serialization process will not be performed. In such case,
NotSerializableException is thrown at runtime.