Hibernate interview 2016

What is Hibernate?
Hibernate is an ORM (Object-relational Mapping) framework, which allows the developer to concentrate on business logic by taking care of persistence of data by itself. Java developer can write code using object and Hibernate can take care of creating those object from data loaded from the database and saving update back to the database

ORM-objecct relational mapping) transfer to data in the form of object between application and database.

 

Q- difference between get() and load() method?load:-

 

difference between get() and load() method is that load() will throw an exception if an object with id passed to them is not found, but get() will return null. Another important difference is that load can return proxy without hitting the database unless required (when you access any attribute other than id) but get() always go to the database, so sometimes using load() can be faster than the get() method. It makes sense to use the load() method if you know the object exists but get() method if you are not sure about object's existence.

Q-When to use load and which one is best ?

ans-

Q-When to use get and which one is best ?

ans- 

Q-What is the difference between save() and persist() method in Hibernate? (detailed answer)
Main difference between save() and persist() method is that, save returns a Serializable object while return type of persist() method is void, so it doesn't return anything. Here is a nice diagram which explains the state transition in Hibernate:

Does Hibernate Session interface is thread-safe in Java? (detailed answer)
No, Session object is not thread-safe in Hibernate and intended to be used with-in single thread in the application.

Does SessionFactory is thread-safe in Hibernate? (detailed answer)
SessionFactory is both Immutable and thread-safe and it has just one single instance in Hibernate application.

What is Hibernate Query Language (HQL)? (detailed answer)
Hibernate query language, HQL is an object-oriented extension to SQL. It allows you to query, store, update, and retrieve objects from a database without using SQL

When do you use merge() and update() in Hibernate? (detailed answer)

You should use update() if you are sure that the Hibernate session does not contain an already persistent instance with the same id and use merge() if you want to merge your modifications at any time without considering the state of the session.