java.io.ObjectInputStream cannot be resolved. It is indirectly referenced from required .class files - due to Serializable

Question

I am practicing a simple Hibernate program and ran into the strange issue.

My Model :

public class Employee implements java.io.Serializable {

// Fields

private Integer empId;
private String empName;
private BigDecimal empSal;

//setters and getters

My Test class :

   public static void main(String[] args) {

    Configuration config =  new Configuration();
    config.configure("hibernate.cfg.xml");

    SessionFactory factory = config.buildSessionFactory();

    Session session = factory.openSession();

    Employee emp = new Employee();
    emp.setEmpName("abc");
    emp.setEmpSal(new BigDecimal("100000"));

    Transaction t = session.beginTransaction();
    session.save(emp);
    t.commit();
    System.out.println("Object Saved Succesfully!!");

    session.close();
    factory.close();

}

exception I am getting :

Exception in thread "main" org.hibernate.InstantiationException: could not instantiate test objectcom.gbn.model.Employee
    at org.hibernate.engine.UnsavedValueFactory.instantiate(UnsavedValueFactory.java:25)
    at org.hibernate.engine.UnsavedValueFactory.getUnsavedIdentifierValue(UnsavedValueFactory.java:44)
    at org.hibernate.tuple.PropertyFactory.buildIdentifierProperty(PropertyFactory.java:44)
    at org.hibernate.tuple.entity.EntityMetamodel.<init>(EntityMetamodel.java:123)
    at org.hibernate.persister.entity.AbstractEntityPersister.<init>(AbstractEntityPersister.java:434)
    at org.hibernate.persister.entity.SingleTableEntityPersister.<init>(SingleTableEntityPersister.java:109)
    at org.hibernate.persister.PersisterFactory.createClassPersister(PersisterFactory.java:55)
    at org.hibernate.impl.SessionFactoryImpl.<init>(SessionFactoryImpl.java:226)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1294)
    at com.gbn.test.Test.main(Test.java:19)
Caused by: java.lang.reflect.InvocationTargetException
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
    at java.lang.reflect.Constructor.newInstance(Unknown Source)
    at org.hibernate.engine.UnsavedValueFactory.instantiate(UnsavedValueFactory.java:22)
    ... 9 more
Caused by: java.lang.Error: Unresolved compilation problem: 
    The type java.io.ObjectInputStream cannot be resolved. It is indirectly referenced from required .class files

    at com.gbn.model.Employee.<init>(Employee.java:1)
    ... 14 more

If I don't implement Serializable in Employee model, I am able to save data without issue. the issue only when my pojo implements Serializable.

What causing the issue?

I have tried solutions as suggested here and here, but unable to resolve my issue.

hbm file :

<hibernate-mapping>
<class name="com.gbn.model.Employee" table="EMPLOYEE">
    <id name="empId" type="java.lang.Integer">
        <column name="EMP_ID" precision="22" scale="0" />
        <generator class="increment" />
    </id>
    <property name="empName" type="java.lang.String">
        <column name="EMP_NAME" length="20" />
    </property>
    <property name="empSal" type="java.math.BigDecimal">
        <column name="EMP_SAL" precision="22" scale="0" />
    </property>
</class>