<hibernate-mapping>
  <class name="contacts.employee" table="contacts">
      <meta attribute="class-description"></meta>
    <id column="contactId" name="contactId" type="string">
      <generator class="assigned"/>
    </id>
    <property column="contactName" length="100" name="contactName" not-null="true" type="string"/>
    <property column="password" length="100" name="password" not-null="true" type="string"/>
    <set cascade="all" name="groupOfResponsibilities" table="employee_responsibilty">
      <key column="contactId"/>
      <many-to-many class="contacts.responsibilities" column="responsibilityId"/>

    </set>

  </class>
</hibernate-mapping>

<hibernate-mapping>
  <class name="contacts.responsibilities" table="responsibilities">
    <meta attribute="class-description">
        This class list of responsibilities if an employee
    </meta>
    <id column="responsibilityId" name="responsibilityId" type="long">
      <generator class="increment"/>
    </id>
    <property column="responsibilityName" name="responsibilityName" type="string"/>
  </class>
</hibernate-mapping>

<hibernate-configuration>
  <session-factory>
    <property name="hibernate.dialect">org.hibernate.dialect.MySQLInnoDBDialect</property>
    <property name="hibernate.connection.driver_class">com.mysql.jdbc.Driver</property>
    <property name="hibernate.connection.url">jdbc:mysql://localhost:3306/****</property>
    <property name="hibernate.connection.username">*****</property>
    <property name="hibernate.connection.password">*****</property>
    <property name="hibernate.hbm2ddl.auto">update</property>
    <property name="hibernate.show_sql">true</property>
    <mapping resource="contacts/employee.hbm.xml"/>
    <mapping resource="contacts/responsibilitiy.hbm.xml"/>
  </session-factory>
</hibernate-configuration>

public class Main {

    public static void main(String[] args) {

        SessionFactory sessionfactory = NewHibernateUtil.getSessionFactory();
        Transaction transaction = null;
        try {
            Session session = sessionfactory.openSession();
            transaction = session.beginTransaction();
            Set<responsibilities> groups = new HashSet<responsibilities>();
            responsibilities responsibilityOne=new responsibilities("Java");
            responsibilities responsibilityTwo=new responsibilities("SQL");
            responsibilities responsibilityThree=new responsibilities("Oracle");
            groups.add(responsibilityOne);
            groups.add(responsibilityTwo);
            groups.add(responsibilityThree);
            String uuid = UUID.randomUUID().toString();
            String uuid2 = UUID.randomUUID().toString();
            employee firstEmployee;
            firstEmployee = new employee(uuid, "Mike", groups);
            employee secondEmployee = new employee(uuid2, "Marc", groups);
            session.save(responsibilityOne);
            session.save(responsibilityTwo);
            session.save(responsibilityThree);
            session.save(firstEmployee);
            session.save(secondEmployee);

            transaction.commit();
        } catch (HibernateException e) {
            transaction.rollback();
            e.printStackTrace();
        } finally {

        }

    }
}

<property name="hibernate.hbm2ddl.auto">create</property>

@Entity
public class Employee {
  @Id
  @GeneratedValue
  private String empID;
  private String name;
}

<property name="hibernate.hbm2ddl.auto">create-drop</property>

<property name="hibernate.hbm2ddl">create-drop</property>