What is@ MappedSuperclass?

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 is @EmbeddedId?

@EmbeddedId is used for composite primary key. i.e. more than one column behaves jointly as primary key. We need to create an entity as Embeddable and the Embeddable entity can be embedded in other entity to achieve composite primary key. Person.java.

What is the advantages of JDBC over JPA?

The most obvious benefit of JDBC over JPA is that it’s simpler to understand. On the other side, if a developer doesn’t grasp the internal workings of the JPA framework or database design, they will be unable to write good code.

What is DiscriminatorColumn?

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 do I use PrimaryKeyJoinColumn?

Example: Customer and ValuedCustomer subclass @Entity @Table(name=”CUST”) @Inheritance(strategy=JOINED) @DiscriminatorValue(“CUST”) public class Customer { } @Entity @Table(name=”VCUST”) @DiscriminatorValue(“VCUST”) @PrimaryKeyJoinColumn(name=”CUST_ID”) public class ValuedCustomer extends Customer { }

What is @IdClass?

The @IdClass annotation takes a value parameter of Class type, which must be the class to be used as the compound primary key. The fields that correspond to the properties of the primary key class to be used must all be annotated with @Id .

What is @ElementCollection?

Annotation Type ElementCollection. @Target(value={METHOD,FIELD}) @Retention(value=RUNTIME) public @interface ElementCollection. Defines a collection of instances of a basic type or embeddable class. Must be specified if the collection is to be mapped by means of a collection table.

What is DiscriminatorValue?

Annotation Type DiscriminatorValue Specifies the value of the discriminator column for entities of the given type. The DiscriminatorValue annotation can only be specified on a concrete entity class.

What is a JPA inheritance?

JPA Inheritence Overview Inheritence is a key feature of object-oriented programming language in which a child class can acquire the properties of its parent class. This feature enhances reusability of the code. The relational database doesn’t support the mechanism of inheritance.

What is Primarykeyjoincolumn?

It is used to join the primary table of an entity subclass in the JOINED mapping strategy to the primary table of its superclass; it is used within a SecondaryTable annotation to join a secondary table to a primary table; and it may be used in a OneToOne mapping in which the primary key of the referencing entity is …

What is joinColumns and inverseJoinColumns?

joinColumns: Assign the column of third table related to entity itself. inverseJoinColumns: Assign the column of third table related to associated entity.

What is the latest version of JPA?

Jakarta Persistence 3.0 The JPA was renamed as Jakarta Persistence in 2019 and version 3.0 was released in 2020.

Is JPA a framework?

By itself, JPA is not a tool or framework; rather, it defines a set of concepts that guide implementers. While JPA’s object-relational mapping (ORM) model was originally based on Hibernate, it has since evolved.

What is CollectionTable?

The ElementCollection values are always stored in a separate table. The table is defined through the @CollectionTable annotation or the element. The CollectionTable defines the table’s name and @JoinColumn or @JoinColumns if a composite primary key.

What is @LazyCollection?

We use the @LazyCollection annotation when we need to take care of the performance in our application. Starting from Hibernate 3.0, @LazyCollection is enabled by default. The main idea of using the @LazyCollection is to control whether the fetching of data should be using the lazy approach or the eager one.