Hibernate ORM or simply Hibernate is a tool for object-relational mapping for Java programming language.
Hibernate provides a framework for mapping an object-oriented domain model to a relational database. It handles object-relational impedance mismatch problems.
This is done by replacing direct, persistent database accesses with high-level object handling functions. Hibernate is distributed under the GNU Lesser General Public License 2.1. Moreover, is free to use.
The most common Hibernate Interview Question is about the functions and the advantages of Hibernate.
We have listed some of the advantages of using hibernate are:
- Hibernate performs the mapping of Java classes to database tables using XML files while keeping every line of the code same.
- For storing and retrieving Java objects directly to and from the database by providing simple APIs
- If you want to affect some changes in the database or any table, you need not go through an elaborate process; you only need to change the XML file properties.
- Forms an abstract of the unknown SQL types and provides a way to work around on the simple Java Objects.
- An application server is not necessary for hibernate to operate.
- Minimizes database access with smart fetching strategies.
- Hibernate is based on a layered architecture which helps the user to operate without having to know all the underlying APIs. Hibernate employs database and configuration data to provide persistence services and persistent objects to the applications.
- It removes the much repetitive code from the JDBC API, and therefore, the code is easier to read, write, and support.
- Hibernate Query Language (HQL) is fully object-oriented and more close to the Java programming language comparing to SQL in JDBC. Also, HQL is a Database-independent query that allows you to switch between different databases easily.
- Hibernate supports caching, which improves performance.
- First-level is a mandatory Session cache.
- Second-level is an optional cache. Hibernate has many cache providers for this level; the most popular are EHCache, OSCache, warm cache, JBoss Cache, etc.
- Query-level is an optional cache for query result sets.
- Lazy load that also improves performance.
- Hibernate supports JPA annotations, which mean the code is portable to other ORM frameworks.
- Hibernate has a connection pool.
- You do not need to handle exceptions. Hibernate allows database management (for example creating tables), JDBC can only work with existing DB tables.
- Hibernate supports inheritance, associations, and collections that are not available in the JDBC API.
In essence, Hibernate is a well-built object model which is very useful both in programming and debugging. Building an object, however, is not that easy.
While programming language like Java is object-oriented, which represents data as an interconnected graph of objects, relational database, on the contrary, represents data in a tabular format (like a spreadsheet).
You need to tackle the mismatch between an object model and a relational model if you decide to write such a tier, not to mention the amount of time and work required in programming and debug the model, which is always proportional to the scale of your system.
All these make data persistence difficult.