What is a discriminator value?

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 discriminator Java?

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.

How do you find the value of the discriminator column?

The entity definition: @Entity(name=”Port”) @DiscriminatorColumn(name=”type”, discriminatorType=DiscriminatorType. STRING, length=10) @DiscriminatorValue(value=”port”) @Table(name=”vPorts”) @XmlRootElement(name=”port”) public class PortEntity { …

What is the use of discriminator value in hibernate?

Discriminator is commonly used in SINGLE_TABLE inheritance because you need a column to identify the type of the record. Example: You have a class Student and 2 sub-classes: GoodStudent and BadStudent.

How do you use a discriminator?

The discriminator must apply to the same level of the schema it is declared in (common mistake when using nested objects). Also, it must be used in combination with anyOf , oneOf , or allOf . We represent the discriminator like a pull down menu on the discriminated property.

What is the use of @MappedSuperclass?

You can use the @MappedSuperclass annotation or XML element to define mappings for an abstract or non-persistent superclass, that are inherited by its subclass entities. A mapped superclass is a special type of class that is not persistent itself, but has subclasses that are persistent.

What is inheritance mapping?

Inheritance . The following mapping strategies are used to map the entity data to the underlying database: A single table per class hierarchy. A table per concrete entity class.

What is MappedSuperclass?

Annotation Type MappedSuperclass. @Target(value=TYPE) @Retention(value=RUNTIME) public @interface 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 a discriminator in database?

The discriminator (or partial key) of a weak entity set is the set of attributes that distinguishes among all the entities of a weak entity set on one particular strong entity.

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”.

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.

What are the types of Hibernate inheritance?

There are three inheritance mapping strategies defined in the hibernate:

• Table Per Hierarchy.
• Table Per Concrete class.
• Table Per Subclass.