What is discriminator column in hibernate?
Annotation Type DiscriminatorColumn Specifies the discriminator column for the SINGLE_TABLE and JOINED Inheritance mapping strategies. The strategy and the discriminator column are only specified in the root of an entity class hierarchy or subhierarchy in which a different inheritance strategy is applied.
What is discriminator in JPA?
The discriminator column is always in the table of the base entity. It holds a different value for records of each class, allowing the JPA runtime to determine what class of object each row represents. The DiscriminatorColumn annotation represents a discriminator column.
Can we have more than one discriminator column?
A subclass has exactly 1 discriminator value. You can add additional subclasses under the existing subclass for the extra discriminator values.
Is a mapping requires discriminator column?
The SINGLE_TABLE strategy maps records from the same database table to different entity classes of an inheritance hierarchy. If you want to use this strategy with JPA, your database table needs to have a discriminator column. The value in this column identifies the entity class to which each record shall be mapped.
What is a discriminator value?
The discriminator value is used to define the type of each row. The discriminator value can be generated using 3 different strategies in the backend configuration wizard: {hash} –the default strategy. When {hash} or nothing is specified the discriminator column value will be the same as the class id.
What is lazy loading in hibernate?
Lazy setting decides whether to load child objects while loading the Parent Object. You need to do this setting respective hibernate mapping file of the parent class. Lazy = true (means not to load child)By default the lazy loading of the child objects is true.
Can we extend entity class?
Entity classes can extend non-entity classes, and non-entity classes can extend entity classes. Entity classes can be both abstract and concrete.
Which inheritance strategy is better in Hibernate?
Single Table. The single table strategy maps all entities of the inheritance structure to the same database table. This approach makes polymorphic queries very efficient and provides the best performance.
What is Dtype in Hibernate?
3.1. Since the records for all entities will be in the same table, Hibernate needs a way to differentiate between them. By default, this is done through a discriminator column called DTYPE that has the name of the entity as a value.
What is discriminator type?
Annotation Type DiscriminatorColumn Specifies the discriminator column for the SINGLE_TABLE and JOINED Inheritance mapping strategies. The strategy and the discriminator column are only specified in the root of an entity class hierarchy or subhierarchy in which a different inheritance strategy is applied.
How many layers are available in Hibernate architecture?
four layersThe Hibernate architecture is categorized in four layers. This is the high level architecture of Hibernate with mapping file and configuration file.
What is MappedSuperclass in JPA?
Annotation Type MappedSuperclass Designates a class whose mapping information is applied to the entities that inherit from it. A mapped superclass has no separate table defined for it.
What is discriminator column in Entity Framework?
The Entity Framework Core Fluent API HasDiscriminator method is used to configure aspects of the discriminator column in a table that represents an inheritance hierarchy. By convention, a discriminator column will be configured to use a string data type will be named "Discriminator".
What is Mappedsuperclass?
A mapped superclass is a special type of class that is not persistent itself, but has subclasses that are persistent. A mapped superclass is useful for defined a common persistence superclass that defines common behavior across a set of classes, such as an id or version attribute.
What are JPA implementations?
The JPA implementation is typically called persistence provider. The mapping between Java objects and database tables is defined via persistence metadata. The JPA provider will use the persistence metadata information to perform the correct database operations.
How is inheritance implemented in hibernate?
There are three inheritance mapping strategies defined in the hibernate: Table Per Hierarchy. Table Per Concrete class. Table Per Subclass.