About persist

api-jpa

flush()

Synchronize the persistence context to the underlying database.(Method of javax.persistence.EntityManager)

 
api-jpa

GenerationType.IDENTITY

Indicates that the persistence provider must assign primary keys for the entity using a database identity column.(Enum Constant of javax.persistence.GenerationType)

 
api-jpa

GeneratedValue.strategy

(Optional) The primary key generation strategy that the persistence provider must use to generate the annotated entity primary key.(Annotation Element of javax.persistence.GeneratedValue)

 
manual

JPA / JDO Class Enhancer

The Enhancer is a post compilation tool that improves performance by modifying the byte code of compiled classes after compilation. ObjectDB Enhancer is a post compilation tool that improves performance by modifying the byte code of compiled classes after compilation. Enhancement is mainly for user-defined persistable classes ( entity classes , embeddable classes and mapp ...

 
forum_thread

Storing objects problem

I want to save this object to database: @Entity public class Device { private String name; private String type; private String ipAddress; private Device parent; @Id private String ID; private String ID_HZMO; @ElementCollection private List<Device> children; }    ... Device dev : deviceList ) { em. persist ( dev ) ; }   em. ... ) . begin ( ) ; em. persist ( router ) ; em. getTransaction ( ...

 
forum_thread

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: ... parent = new Nodes ( ) ; em. persist ( parent ) ; queue. add ( parent ) ... left. setParent ( cur ) ; em. persist ( left ) ; ++ iNum ; Nodes right = new ...

 
api-jpa

javax.persistence.Transient

Specifies that the property or field is not persistent.(Annotation of JPA)

 
api-jpa

javax.persistence.EmbeddedId

Applied to a persistent field or property of an entity class or mapped superclass to denote a composite primary key that is an embeddable class.(Annotation of JPA)

 
api-jpa

javax.persistence.NamedQueries

Specifies multiple named Java Persistence query language queries.(Annotation of JPA)

 
api-jpa

createQuery(qlString)

Create an instance of Query for executing a Java Persistence query language statement.(Method of javax.persistence.EntityManager)