Object Relational Mapping (ORM)
ORM is a technique for conversion of data between in-compatible type systems in object - oriented languages.Databases do not use the concept of Object Oriented languages wherein we associate objects to demonstrate the state of the systems. Database map values to primitive datatypes such as integer, real , float , String etc .Consider an example - You have to insert an employee details into the database.If we use contemporary technique you need to convert that employee details to primitive value i.e. formulate an insert/update query with these details for that employee and then insert/update to the database.
This problem is solved by ORM .
The Object Relational Mapping transforms any object data member type to a corresponding relational database (SQL) data source representation in any supported relational database. Relational mappings let you map an object model into a relational data model.
Relational mappings transform object data members to relational database fields. Use them to map simple data types including primitives (such as
int), JDK classes (such as String), and large object (LOB) values. You can also use them to transform object data members that reference other domain objects by way of association where data source representations require object identity maintenance (such as sequencing and back references) and possess various types of multiplicity and navigability. The appropriate mapping class is chosen primarily by the cardinality of the relationship.
Some ORM supporting APIs
Java -
- Hibernate
- MyBatis, free open source, formerly named iBATIS
- ActiveJDBC - Java implementation of Active record pattern, inspired by Ruby on Rails
.Net
- ADO.NET Entity Framework, included in .NET Framework 3.5 SP1 and above
- iBATIS, free open source, maintained by ASF but now inactive.
- NHibernate, open source
- NHydraate, open source
