Editing Hibernate (framework) (section)

==Mapping==
The mapping of Java classes to database tables is implemented by the configuration of an [[XML]] file or by using [[Java annotation|Java Annotations]]. When using an XML file, Hibernate can [[Program synthesis|generate]] skeleton [[source code]] for the persistence classes. This is auxiliary when annotations are used. Hibernate can use the XML file or the Java annotations to maintain the [[database schema]].

There are provided facilities to arrange [[One-to-many (data model)|one-to-many]] and [[Many-to-many (data model)|many-to-many]] relationships between classes.{{sfn|Bauer|King|Gregory|2015}}{{rp|§=7|pp=140–171}} In addition to managing associations between objects, Hibernate can also manage [[Reflexive relation|reflexive]] associations wherein an object has a one-to-many relationship with other instances of the [[Class (computer programming)|class]] [[data type|type]].

Hibernate supports the mapping of custom value types. This makes the following scenarios possible:
* Overriding the default SQL type when mapping a column to a property.
* Mapping Java [[Enumerated type|Enums]] to columns as though they were regular properties.{{sfn|Bauer|King|Gregory|2015}}{{rp|§=5.1.7|pp=89–90}}
* Mapping a single property to multiple columns.

'''Definition:'''
Objects in an [[Object-oriented programming|object-oriented]] application follow [[object-oriented programming|OOP]] principles, while objects in the back-end follow [[database normalization]] principles, resulting in different representation requirements. This problem is called "[[object–relational impedance mismatch]]". Mapping is a way of resolving the object–relational impedance mismatch problem.

Mapping informs the ORM tool of what Java class object to store in which database table.