java.io.NotSerializableException

java.io.NotSerializableException is thrown when the object is not eligible for the serialization. You must implement the Serializable interface to make the class eligible for the serialization. This is a marker interface which tells the JVM that the class can be serialized. Look at the below example.

Employee.java

Employee class which not implementing the serializable interface.

package javabeat.net.io;

public class Employee {
	private String id;

	public String getId() {
		return id;
	}

	public void setId(String id) {
		this.id = id;
	}
}

NotSerializableExceptionExample.java

This class tries to serialize the object by writing to the ObjectOutputStream. However, it throws the exception.

package javabeat.net.io;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.ObjectOutputStream;

/**
 * java.io.NotSerializableException Example
 *
 * @author Krishna
 *
 */
public class NotSerializableExceptionExample {
	public static void main(String[] args) throws IOException{
		//Create FileOutputStream to create file
		FileOutputStream out = new FileOutputStream("employee.dat");

		//Create ObjectOutputStream
		ObjectOutputStream outputStream = new ObjectOutputStream(out);

		//Create objects
		Employee obj = new Employee();
		obj.setId("001");

		//Write objects to stream
		outputStream.writeObject(obj);

		//Always close the stream
		outputStream.close();
	}
}

java.io.NotSerializableException Thrown

To fix this exception, Employee class must implement the serializable interface.

Exception in thread "main" java.io.NotSerializableException: javabeat.net.io.Employee
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1181)
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)
	at javabeat.net.io.NotSerializableExceptionExample.main(NotSerializableExceptionExample.java:13)