Object Relational Mapping Introduction#
What is the Object Relation Mapping (ORM)?#
Object-Relational Mapping (ORM)is a programming technique for converting data between relational databases and object oriented programming languages such as Java, C#, etc.- An
ORMsystem has the following advantages over plain JDBC.
| No. | Advantages |
|---|---|
| 1 | Let’s business code access objects rather than DB tables. |
| 2 | Hides details of SQL queries from OO logic. |
| 3 | Based on JDBC |
| 4 | No need to deal with the database implementation. |
| 5 | Entities based on business concepts rather than database structure. |
| 6 | Transaction management and automatic key generation. |
| 7 | Fast development of application. |
An ORM solution consists of the following four entities
| No. | Solutions |
|---|---|
| 1 | An API to perform basic CRUD operations on objects of persistent classes. |
| 2 | A language or API to specify queries that refer to classes and properties of classes. |
| 3 | A configurable facility for specifying mapping metadata. |
| 4 | A technique to interact with transactional objects to perform dirty checking, lazy association fetching, and other optimization functions. |
- There are several persistent frameworks and ORM options in Java. A persistent framework is an ORM service that stores and retrieves objects into a relational database.
- TopLink
- Hibernate
- And many more
- We will mainly focus on
Hibernatebecause it is the most popular one.