Can anybody explain me the purpose of having the ejbPostCreate<method> , what are the responsibity of ejbCreate<method> and what left to do in the post create method and one more thing if there is no create method , then how entity will be created ,is it created by finder method ?
I won't give you a full answer, as it is too long to explain. Basically, after ejbCreate has been called, the entity exists and has a primary key. What you can do in doPostCreate is setting the CMR fields for example. You can get the primary key by calling getPrimaryKey(). You can pass a reference to the component interface of the bean to another bean.
if there is no create method , then how entity will be created ,is it created by finder method ?
You're misunderstanding the concept of ejbCreate. ejbCreate will insert some data in a persistent store. Finder methods only looks for data, and the retrieved data is set into a bean by the container. Create methods are not called here.