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

Apart from Persistence i.e. saving and loading data from Database, Hibernate also provides the following benefits

• Caching
• Lazy Loading
• Relationship management and provides code for mapping an object to the data
•  The developer is free from writing code to load/store data into the database.

This is again a follow-up to the previous Hibernate interview question. The first level cache is maintained at the Session level while the second level cache is maintained at a SessionFactory level and shared by all sessions. You can read these books to learn more about caching in Hibernate.

There are two ways to map Java objects to a relational table:

• Using XML based hibernate mapping
• Annotation-based hibernate mapping

Accordion Content 

• The key difference between the get() method and load() method is that load() method will throw an exception if an object with id passed to them is not found, but get() method will return null.
• The second important difference is that load() method can return proxy without hitting the database unless required (when you access any attribute other than id) but the get() method always go to the database, so sometimes using the load() method can be faster than the get() method.

• Hibernate Named Query helps us in grouping queries at a central location rather than letting them scattered all over the code.
• Hibernate Named Query syntax is checked when the hibernate session factory is created, thus making the application fail fast in case of any error in the named queries. Hibernate Named Query is global, which means once defined it can be used throughout the application.
• However one of the major disadvantages of a Named query is that it’s hard to debug because we need to find out the location where it’s defined.

 An Object Relational Mapping (ORM) tool helps to simplify data creation, manipulation, and access by internally using Java API to interact with the databases. It’s a technique that maps objects stored in a database.

Hibernate outclasses JDBC because:

•  Hibernate code is cleaner and more readable thanks to the elimination of boiler-plate code, something found in JDBC
• Unlike JDBC API, Hibernate supports associations, collections, and inheritances
• HQL (Hibernate Query Language) is closer to Java and is more object-oriented
• Developers don’t need to write code to store and load data into the database
• Hibernate enables faster application development

Hibernate supports databases like:

• DB2/NT
• FrontBase
• HSQL Database Engine
• Informix Dynamic Server
• Microsoft SQL Server Database
•  MySQL