Hibernate is an Object-Relational Mapping (ORM) framework that is used to map an object-oriented domain model to a relational database. Initially, the developers used Structured Query Language (SQL) to query and retrieve data from a database. In such a scenario, the developers need to provide additional Java code in the application to handle the resultsets containing the data retrieved from the database.
With the introduction of the Hibernate framework, the JavaBean classes can now directly be mapped to the database tables, eliminating the need to provide the additional Java code in the applications to handle query results. The Hibernate framework automatically generates the SQL calls and ensures that a Web application is portable with all SQL supported databases. This framework also provides the persistence feature for Plain Old Java Objects (POJOs). You can use the Hibernate framework not only in a Java Platform, Standard Edition (J2SE) application but also in the Java EE applications using servlets or Enterprise JavaBeans (EJB) session beans.
Introduction
The Hibernate framework is a lightweight ORM, which is a technique for mapping an object model to a relational model. This framework handles mapping from Java classes to database tables and provides Application Programming Interface (API) for querying and retrieving data from a database.
Earlier, JDBC and SQL were used to retrieve data from a database; however, writing queries using SQL to insert, retrieve, update, or delete data from a database was a time-consuming process This was simplified with the introduction of Hibernate that provides HQL. As compared to SQL in HQL, you do not need to write code to perform common data persistence related programming tasks.
Hibernate uses a transparent programming model for mapping Java objects to relational databases. To provide mapping for Java objects, you need to write a simple POJO class and create an Extensible Markup Language (XML) mapping file. This XML file describes the relationship of the database with the class attributes and calls the Hibernate APIs to load/store the persistent objects.
Hibernate establishes the relationship between object-oriented systems and relational databases. It allows transparent persistence that enables the applications to use any Relational Database Management System (RDBMS) software.
Hibernate works efficiently with applications that use swings, servlets, and EJB session beans. The developer does not need to implement an interface or extend classes for persistence, as Hibernate provides extensive support of Java collections API (Map, Set, List, SortedMap, Sorted Set, and Collection).
After being familiar with the Hibernate framework, let’s now try to understand the need for Hibernate framework to develop a Web application.
Need of Hibernate Framework
The Hibernate framework provides an extensive approach to manage the object-relational mapping and persistence management. The following are the reasons due to which Hibernate in a Web application can be used to query or retrieve data from a database:
- Supports object-oriented programming models, such as inheritance, polymorphism, composition, abstraction, and the Java collections framework.
- Provides developers with a persistence feature and a code generation library (CGLIB) that helps in extending Java classes and implementing Java interfaces at runtime environment. The changes that are made to objects associated with a transaction are automatically addressed in the database. This saves the time spent in extra coding for bytecode processing.
- Provides object-oriented query language called HQL, which is similar to SQL. HQL is an ORM query language defined in EJB 3.0. It helps in writing multi-criteria search and dynamic queries.
- Provides Object/Relational mapping for bridging the gap between object-oriented systems and relational databases.
- Enable the developer to build a Hibernate Web application very efficiently in MyEclipse by using Hibernate eclipse plugin that provide mapping editor, interactive query prototyping, and schema reverse engineering tool.
- Reduces the development time, as it supports object-oriented programming, such as inheritance, polymorphism, composition, and Java Collection framework.
- Provides ID generator classes to get surrogate keys also called unique keys/identifiers. Some of the classes are: Native, Identity, Sequence, Increment, Hilo and Seqhilo (HI/LO) algorithm and Universally Unique Identifier algorithm.
- Provides a Multi-Level Cache Architecture that ensures thread safety and continuous data access
- Provides features, such as lazy initialization and eager or batch fetching to improve the performance of an application.
- Provides integration with Java EE.
- Operates transactions in a managed or non-managed environment. This facilitates the following tasks:
- SessionFactory can be easily bound to Java Naming and Directory Interface (JNDI)
- Stateful session bean or a HttpSession servlet with load balancing to handle a session
- JDBC connections may be provided by application data source
- Hibernate Transaction system integrates with Java EE applications through Java Transaction API (JTA)
- Automatic binding of the Hibernate session to the global JTA transaction scope
