Hibernate : How to use @Id annotation
Points to remember
- There should be only one @Id annotation in a hibernate entity class.
- There should be at least one field specified as primary id.
- You can use different approaches for creating primary id using these Primary Key Generation Strategies.
How to use @Id annotation in Hibernate
Taking the example in the previous example. @Id annotation tells the hibernate to@Id annotation tells the hibernate that this field will be the primary key of the table.
@Id annotation class looks like the following
@Target({METHOD, FIELD}) @Retention(RUNTIME) public @interface Id { }
If we do not add @Id annotation on any of the fields in Hibernate entity then you will get the following error.
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:1249) at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.access$600(EntityManagerFactoryBuilderImpl.java:120) at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:860) at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:850) at org.hibernate.boot.registry.classloading.internal.ClassLoaderServiceImpl.withTccl(ClassLoaderServiceImpl.java:425) at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:849) at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:60) at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:343) at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:318) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1633) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1570) ... 15 more Caused by: org.hibernate.AnnotationException: No identifier specified for entity: com.ekiras.domian.User at org.hibernate.cfg.InheritanceState.determineDefaultAccessType(InheritanceState.java:277) at org.hibernate.cfg.InheritanceState.getElementess(InheritanceState.java:224) at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:775) at org.hibernate.cfg.Configuration$MetadataSourceQueue.processAnnotatedClassesQueue(Configuration.java:3845) at org.hibernate.cfg.Configuration$MetadataSourceQueue.processMetadata(Configuration.java:3799) at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1412) at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1846) at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl$4.perform(EntityManagerFactoryBuilderImpl.java:857) ... 23 common frames omitted
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