Application session is shared between users while accessing from different machines - spring

Question

I am building an online Examination project with spring mvc and Hibernate as Frameworks and it is almost done, Now I am getting the problem with session
xml configuration of the session
<beans:bean id="hibernate4AnnotatedSessionFactory"
class="org.springframework.orm.hibernate4.LocalSessionFactoryBean">
<beans:property name="dataSource" ref="dataSource" />
<beans:property name="annotatedClasses">
<beans:list>
<beans:value>com.app.spring.model.Result</beans:value>
</beans:list>
</beans:property>
<beans:property name="hibernateProperties">
<beans:props>
<beans:prop key="hibernate.dialect">org.hibernate.dialect.MySQLDialect
</beans:prop>
<beans:prop key="hibernate.show_sql">true</beans:prop>
<beans:prop key="hibernate.hbm2ddl.auto">true</beans:prop>
</beans:props>
</beans:property>
</beans:bean>
<!-- Inject the transaction manager -->
<tx:annotation-driven transaction-manager="transactionManager"/>
<beans:bean id="transactionManager" class="org.springframework.orm.hibernate4.HibernateTransactionManager">
<beans:property name="sessionFactory" ref="hibernate4AnnotatedSessionFactory" />
</beans:bean>
and queries in dao impl are like this
#Override
public void addObject(Object p) {
Session session = this.sessionFactory.getCurrentSession();
session.persist(p);
logger.info("Customer saved successfully, Customer Details=" + p);
}
The Exam users will login to application and he have to attempt 20 questions
The application is in my local machine and which is connected with in network for testing While the Exam is started with two people I am getting the problem like below
Exam pattern is to attempt 20 questions if two people started exam suppose one attempted 10 questions and other attempted 10 questions then the exam is getting completed I am thinking that the session is divided between the users can any one help me how can I overcome this problem.