About GeneratedValue
Auto Generated Values
Explains the different strategies for generating auto values (mainly for primary key fields) in JPA. Marking a field with the @GeneratedValue javax.persistence.GeneratedValue JPA annotation Provides for the specification of ... values for primary key fields annotated by @GeneratedValue javax.persistence.GeneratedValue JPA annotation ...
JPA Annotations for Value Generation
Reference (JavaDoc) of JPA 2 value generation annotations, including @GeneratedValue, @SequenceGenerator and @TableGenerator.... key) persistent fields. At the field level, the @GeneratedValue with an optional GenerationType strategy is specified: javax.persistence.GeneratedValue javax.persistence.GenerationType The ...
javax.persistence.GeneratedValue
Provides for the specification of generation strategies for the values of primary keys.(Annotation of JPA)
New entity objects are duplicated on merge cascading
When merge is cascaded to a new entity object that has not been persisted yet - it becomes persisted twice. This was demonstrated by a Java EE application in this forum thread but may be reproduced also in a simple console test case: ... Book { @ Id @ GeneratedValue ( strategy = GenerationType . AUTO ... { @ Id @ GeneratedValue ( strategy = GenerationType . AUTO ...
Can a Set<E> be a foreign key?
I have two classes, Cell and Character. Basically, the cell is like a room, and contains a variable (private Set<Long> cellHeldCharacters;) which holds the IDs of the characters within the cell (The IDs are Primary Keys). Can I use the Foreign Key annotation for the variable, or is it illegal/unrecommended to do it for a Set? For a better picture, I have: ... Character { @ Id @ GeneratedValue private long characterId ; private ... Cell { @ Id @ GeneratedValue private long cellID ; private String ...
Join performance in Objectdb
select count(e) from Meta e, ImageNet i, Page p where e.idImage=i.id and e.idPage=p.id; So simple a command cause me half an hour and is running now! Each table has about 160K records. What formula can predict the time for such counting? TIA ... class A { @ Id @ GeneratedValue long id ; B b ; long bId ; ... class B { @ Id @ GeneratedValue ( strategy = GenerationType . SEQUENCE ...
find() cost unreasonable time!
Hi, I make a full binary tree of 4095 node, I check the first 9 node, but the root cost 24 seconds, why? Result: ... class Nodes { @ Id @ GeneratedValue ( strategy = GenerationType . IDENTITY ... FetchType ; import javax. persistence . GeneratedValue ; import javax. persistence . GenerationType ...
javax.persistence.TableGenerator
Defines a primary key generator that may be referenced by name when a generator element is specified for the GeneratedValue annotation.(Annotation of JPA)
mappedBy problem
If I put the mappedBy element to the @OneToMany, the owned side (the many side) will never persist ! for example @Entity public class Employee { @Id @GeneratedValue(strategy = GenerationType.IDENTITY) public Long id; public String name; @OneToMany(targetEntity=Address.class,mappedBy="employee") public List<Address> addresses; } @Entity... class Employee { @ Id @ GeneratedValue ( strategy = GenerationType . IDENTITY ... class Address { @ Id @ GeneratedValue ( strategy = GenerationType . IDENTITY ...
Bug: ClassCastException by retrieval
Hi, when a generic array put into ObjectDB, its type changed to Object[]! codes: ... ; import javax. persistence . GeneratedValue ; import javax. persistence . GenerationType ... { @ Id @ GeneratedValue ( strategy = GenerationType . IDENTITY ...
