Monday, November 12, 2018

Hibernate - Basic Annotations

Greetings!

  • @Entity - Add in class level. Declares that this class is an entity

@Entity
public class Employee {
    // ...
}


  • @Table - Add in class level. Define table, schema, catalog. Use name property to add the name of the table unless class name is used as the table name.

@Entity
@Table(name = "tbl_employee")
public class Employee {
    // ...
}


  • @Column - Add column properties.

@Column(name = "first_name")
private String firstName;


  • @Id - Declares property as the identifier of this class.

@Id
private Long id;


  • @GeneratedValue - use along with @Id to generate primary key automatically. JPA defines 5 strategies.

@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Long id;


AUTO - select depending on the underlying database.
IDENTITY
SEQUENCE
TABLE
identity copy - identity is copied form another entity.

  • @Version - Adding this will add optimistic locking capability. For an update query Hibernate will automatically add version number validity in where clause. Numeric is preferred but a timestamp can also be used.

@Version
@Column(name="optimistic_lock")
private Integer version;


  • @Temporal - Use to mark date field format like DATE (date only), TIME (time only) or TIMESTAMP (date and time).

@Column(name = "dob")
@Temporal(TemporalType.DATE)
private Date dateOfBirth;


  • @Enumerated - Use to map enum. By default it used enum's ordinal and EnumType can be used to override default behaviour.

@Column(name = "employee_type")
@Enumerated(EnumType.STRING)
private EmployeeType employeeType;


  • @Embedded - Define to use value object inside the entity class.
  • @Embeddable - Define a value object to use in an entity.
  • @Transient - Skip persisting a property.



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