ORM Tools in Java

ORM stands for Object Relation Mapping. It is a middleware application or tool that sits between the web application and database. It wraps the implementation specific details of storage drivers in an API.

What is ORM?

ORM is a technique for converting data between Java objects and relational databases (table). In simple words, we can say that the ORM implements responsibility of mapping the object to relational model and vice-versa. the ORM tool does mapping in such a way that model class becomes a table in the database and each instance becomes a row of the table.

Advantages of ORM Tool

It saves time and efforts.
It gives pace to development process.
It reduces the development cost.
It provides connectivity to the database.
It makes development more object-oriented.
Easy transaction management.
No need to implement database manually.
Modification in any model (object or relational model) does not affect each other.

ORM Tools

There are many ORM tools available but the following ORM tools are the most commonly used.

Hibernate
TopLink
EclipseLink
OpenJPA
MyBatis (formally known as iBatis)

Hibernate

Hibernate is a Java persistence framework that simplifies the development of Java application to interact with the database. It is an open source, widely used, lightweight, ORM tool. Hibernate implements the specifications of JPA (Java Persistence API) for data persistence.

Advantages of Hibernate

It is an open source, lightweight, flexible, and powerful ORM tool.
It supports database independent query (HQL).
Its performance is fast because cache is internally used.
It simplifies the complex join.
If there is any modification in table or database only need to change in XML file properties.

TopLink

TopLink is an ORM tool developed by Oracle especially for Java developers. It is a persistence framework that is a part of Oracle's OracleAS, WebLogic, OC4J servers. It provides development tools and run-time functionalities that ease the development process and increases the functionality. Persistent object data is stored in relational databases that helps build high-performance applications. Storing data in either XML (Extensible Markup Language) or relational databases is made possible by transforming it from object-oriented data.

Advantages of TopLink

Provides GUI interface for defining mapping.
More flexible mapping types.
Independence between object model and SQL schema.
It provides development flexibility like code business logic into model, developer can deal with an existing model.
It provides more flexible mapping types.

OpenJPA

Apache OpenJPA is a Java persistence project at The Apache Software Foundation that can be used as a stand-alone POJO persistence layer or integrated into any Java EE compliant container and many other lightweight frameworks, such as Tomcat and Spring.

Advantages of OpenJPA

Declarative mapping.
It can be use as stand-alone POJO persistence layer.
It can be easily integrated into any EJB complaint container.

MyBatis

MyBatis was formerly known as iBatis. It is also an open source persistence framework that simplifies the implementation of database. Basically, it performs the following four things:

It executes SQL safely and abstracts away all the intricacies of JDBC.
It maps parameter objects to JDBC prepared statement parameters.
It maps rows in JDBC result sets to objects.

It is different from other ORM tools. The main difference between MyBatis and other ORM tool is that MyBatis emphasis the use of SQL while other ORM tools uses custom query language (HQL).

Advantages of MyBatis

It provides tags instead of using logic code.
It is quite flexible and close to JDBC.
Separation of SQL statements form code.
It supports inline SQL.
Maintenance is easy because it encapsulates SQL in the form of stored procedure.
It also supports dynamic SQL.

EclipseLink

EclipseLink is the open source Eclipse Persistence Services tool introduced by Eclipse Foundation. It is an extensible framework that allows Java developers to interact with various data services such as databases, web services, Object XML mapping, and enterprise information systems. It supports the following four persistence standards: