In this section we will learn about the Hibernate Associations and Joins, which is very important concept of Hibernate framework. Hibernate association allows the developer to represent the database relationships in object oriented way. In this you will learn about the database relationship and the Hibernate relationships. You will also learn how to present these relationships in Hibernate. Hibernate relationships eases the development of persistence layer of complex application involving various types of relationships such as one-to-one, one-to-many etc. We have also provides the appropriate examples of Hibernate associations and joins to help you understand the concepts in better way.
Database Relation ships
All the modern relational databases are very advance and supports various types of relationships for managing the complex relational data in much more intuitive way. Database relationships are importance concept and you should know about this. The relationship concept in database allows you to define relationship (or connection) between the tables of a database. Once the relationship is correctly defined among the tables of the database, you can perform cross-table queries. This way of performing cross-table queries is knows as joins. Database supports simple as well as complex cross-table queries (joins). Relational databases supports following types of relationships:
These four types of relationships are sufficient for managing the complex business data.
The Hibernate ORM supports the association relationships and following components takes parts:
If you use the annotations for mapping the relationship then you can use any of the following annotations as per your requirement:
Types of Hibernate Association mappings
Hibernate framework supports following types of association mappings:
Further each of the above associations are of following types:
Here is the examples of Hibernate associations
Unidirectional Association with join Table
Bidirectional Association with join Table