I have the delete method:

public boolean deleteCustomerByCustomerId(long customerId) {
Session session=getHibernateTemplate().getSessionFactory().openSession();
session.delete(getCustomerByCustomerId(customerId));
return true;
}


and the getCustomerByCustomerId method is:

public TblCustomerInfo getCustomerByCustomerId(long customerId) {
Session session=getHibernateTemplate().getSessionFactory().openSession();
StringBuffer hql=new StringBuffer("from TblCustomerInfo where customerId=:customerId");
Query q=session.createQuery(hql.toString());
q.setParameter("customerId", customerId);
return (TblCustomerInfo)q.uniqueResult();

}


When i call the delete method it give me a error:Illegal attempt to associate a collection with two open sessions


How to slove this problem?

You need to implement some form of session management to ensure you stick to the basic rules:
1. open session
2. start transaction
3. do your work
4. commit transaction
5. close session

What you did was this:
open session1
do work
open session2
do work on session1's objects

How you manage your sessions depends very much on your environment: standalone, app server, spring, etc. Check out 1.2.5 in the the tutorial for basic management using HibernateUtil.
http://www.hibernate.org/hib_docs/v3/reference/en/html/tutorial.html

Thanks a lot.

I'm not sure how you are managing the session, but you might also want to take a look at the getSession method of the Hibernate Session, as opposed to the openSession method.

The getSession method will look for an existing session in the current thread local, or however it is set up in the hibernate.cfg.xml file. On the other hand, opensession will return you a session that expects you to manage the lifecycle of the session. So, getSession may help extra session objects from being created when perhaps they don't need to be.