Java Hibernate is an object-relational mapping tool(ORM) allowing the mapping of object-oriented models to relational databases for web applications by providing a framework. Mapping of entities in a Java class to tables created in a database and mapping from Java data types to SQL data types is one of the primary functions of Hibernate. You can also inquire or retrieve data using Hibernate. It relieves the developer from manually handling the database.
What is Java Hibernate?
Hibernate is the Object-Relational Mapping (ORM) framework in Java created by Gavin King in 2001. It simplifies the interaction of a database and the Java application being developed. It is an ORM tool that is powerful and lightweight. Another important thing is that this is an open-source high-performance tool. Hibernate implements Java Persistence API specifications and is a very powerful object-relational persistence and query service for applications developed in Java.
Understanding Java Hibernate
Java objects and database server interacts with each other via Hibernate. Hibernate will work so as to persist the Java objects depending upon the correct O/R patterns and recognition mechanisms. The architecture of Hibernate is layered such that the user does not really need to know the underlying APIs in order to operate. It is with the help of the database and configuration data that the Hibernate is able to provide persistence services and objects to the application. The architecture of Hibernate consists of objects like a session factory, transaction factory, persistent object, etc.
Hibernate framework uses many objects such as session factory, session, transaction, etc. along with existing Java API such as JDBC (Java Database Connectivity), JTA (Java Transaction API) and JNDI (Java Naming Directory Interface).
There are four layers in Hibernate architecture. These are listed below:
• Layer 1 – Java Application Layer
• Layer 2 – Hibernate Framework Layer
• Layer 3 – Backend API Layer
• Layer 4 – Database Layer
Why do we Need Hibernate in Java?
In order to retrieve data from the database writing repeatedly the same lines of code in your application again and again can be tiring and irritating. Also, switching from one database to another, implementing oops with JDBC, creating associations between database tables require lots of effort and rework if done without using the Hibernate framework. As already told, Java Hibernate is an ORM tool that helps ease all these issues faced while using JDBC for database connectivity.
When compared to JDBC, Hibernate will connect itself with the database. In order to execute the queries, Hibernate uses Hibernate Query Language or HQL. Once the queries have been executed Hibernate will then perform the mapping of the results to their respective application layer. This mapping results in objects totally based on the properties mentioned in the configuration XML file of Hibernate. A session does not only help an application in creating a connection with the database but also works toward saving and fetching the persistent object in Hibernate. Using Session factory (which is an interface) one can create an instance of a session and use this instance just that there should only be one session factory for every database. For example, if an application is using two databases namely- MySQL and Oracle, one session factory should be maintained for MySQL and one session factory should be maintained for Oracle. No two session factory can be maintained for Oracle or MySQL alone.
Advantages of Java Hibernate
Object Relational Mapping or ORM is an answer to the problem of mapping the Object Domain Model to relational persistence collection easily. Hibernate is available for free and an open sourced object-relational mapping library for Java specifically built to map objects to any Relational Database Management System. It is also useful in implementing the concepts of object-oriented programming in a relational database.
Let us have a look at some of the main advantages we get by implementing ORM-
1.High Yielding: If an application is implemented with the help of JDBC, one of the biggest challenge faced is the time that is spent in developing, tuning and maintaining the code that is relevant to JDBC. The answer to this is ORM. By using ORM, the time taken by an application to be implemented decreases exponentially as there is no need to examine the code and mapping mechanism. The database is efficiently managed by a robust, ready and totally trusted ORM engine.
2.Well Structured: ORM has an effective design pattern which is put into effect and tested well. It does not require redoing an already completed task which is also tried, tested and is being used again thus saving time.
Hibernate implements architectural design pattern of ORM just as similar to other implementations. It has got many pros and cons. Now we’ll list down advantages of using the Hibernate.
They are as under :
1.Database Independent: At the backend, Hibernate is independent of an engine of the database.
2.Built-In Connection Pool Implementation: Hibernate integrates with the most reliable connection pool implementation, that is, C3P0 automatically.
3.Layered Architecture: Hibernate is considered as a layered architecture, thus ensuring that we don’t obligate to make use of everything that is provided by Hibernate. We just make use of those features which we may think are light enough for the project.
4.JPA Provider: Java Persistence API, that is, JPA is considered as a specification. There are a lot of implementations that are available for JPA such as EclipseLink, OpenJPA and many more. It is a standard ORM solution and in addition, encompasses JPA capability. Therefore, usage of hibernating helps us in leveraging all of the capabilities of ORM as well as JPA in JPA-specific projects.
Hibernate is thus an ORM tool used in the mapping of database structures with Java objects at run time. Using of Hibernate which is a persistent framework allows the developers to focus on just business logic code writing despite writing accurate as well as good persistence layer that consists of writing the SQL Queries, connection management, and JDBC Code.