Difference between Serialization and Externalization in Java

Java Object Oriented Programming Programming

Serialization and externalization both are the processes of converting an object to stream byte and storing byte stream in database or memory. The class which implements java.io.Serializable interface can be serialized. On the other hand, externalization used for custom serialization based on the requirement in the application. Externalization extends java.io.Serializable.

Sr. No.	Key	Serialization	Externalization
1	Interface	Serialization is a marker interface	Externalization contains two methods readExternal and writeExternal.
2	Implementation logic	The class which is implementing this interface gives the responsibility to JVM for serializing or persist java object. JVM use readObject and writeObject for serialization	Externalization provides implementation logic control to the application by overriding readExternal and writeExternal methods.
3	Way to ignore variables	In serialization, JVM ignores transient variable during serialization and deserialization of java object	Programmer can write their own logic to ignore some of the variables during externalization of java object
4	Performance	In serializable interface uses reflection which causes relatively slow performance.	Externalizable gives full control over the implementation approach.
5	Object serialization with inheritance	1. If the superclass is not serializable then the subclass still can be serialized. 2. If a subclass is not serialized but superclass is automatically serializable	We can apply this to externalizable as well.

Example of Externalizable

class ExternalizableExample implements Externalizable {
   Integer id;
   @Override
   public void writeExternal(ObjectOutput out) throws IOException {
      out.writeInt( id );
   }
   @Override
   public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException {
      this.id = in.readInt();
   }
}

Example of Serializable

class SerializableExample implements Serializable {
   private static final long serialVersionUID = 5081877L;
   String name;
}

Mahesh Parahar

Updated on 18-Nov-2019 06:52:04

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