Module jakarta.nosql.core
Package jakarta.nosql

Annotation Interface Entity

@Retention(RUNTIME) @Target(TYPE) public @interface Entity
Annotates a class as an entity, representing a persistent class corresponding to a database structure.

Entity classes must adhere to specific rules:

  • At least one field must be annotated with Id or Column.
  • Constructors must be public or protected with no parameters, or with parameters annotated with Column or Id.
  • Annotations at the constructor will build the entity and read information from the database, while field annotations are required to write information to the database.
  • If both a non-args constructor and a constructor with annotated parameters exist, the constructor with annotations will be used to create the entity.
  • Constructor parameters without annotations will be ignored, utilizing a non-arg constructor instead.
  • Entities should not have multiple constructors using Id or Column annotations.
  • Record classes can also serve as entities.

Enums or interfaces cannot be designated as entities.

Each entity must have a unique identifier, typically annotated with Id.

The following example demonstrates two classes, Person and Address, where a person has an address: 


 @Entity
 public class Person {

     @Id
     private Long id;

     @Column
     private String name;

     @Column
     private Address address;
 }

 @Embeddable
 public class Address {
     @Column
     private String street;

     @Column
     private String city;
 }

Note: NoSQL databases may have varying behaviors regarding serialization, resulting in different storage formats based on the NoSQL vendor.

The sample below demonstrates the use of records as entities: 


 @Entity
 public record Person(@Id Long id, @Column String name, @Column Address address) {
 }

 @Embeddable
 public class Address {
     @Column
     private String street;

     @Column
     private String city;

     public Address(@Column String street, @Column String city) {
         this.street = street;
         this.city = city;
     }
 }
Since:
1.0
See Also:

  • Optional Element Summary

    Optional Elements
    Modifier and Type
    Optional Element
    Description
    String
    value
    The name of the entity.

  • Element Details

    • value

      String value
      The name of the entity. If not specified, defaults to the unqualified simple name of the class. This name is used to refer to the entity in queries and also to represent the name in the NoSQL database structure, such as the table name or collection name.

      For example, given the class org.jakarta.nosql.demo.Person, the default name will be Person.

      To customize the name, set the value of the @Entity annotation to the desired name, as shown below: 

      
 @Entity("ThePerson")
 public class Person {
 }
      Returns:
      the entity name (optional)
      Default:
      ""