目录JPA出现错误Noidentifierspecifiedforen问题描述问题原因解决方案Noidentifierspecifiedforentity:XXXX错误原因及其解决
JPA出现错误No identifier specified for en
问题描述启动项目未成功，报错如下：
Error starting ApplicationContext. To display the conditions report re-run your application with ‘debug’ enabled.2019-03-17 13:19:24.391|main|ERROR|org.springframework.boot.SpringApplication.reportFailure:858|Application run failedorg.springframework.beans.factory.BeanCreationException: Error creating bean with name ‘entityManagerFactory’ defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaConfiguration.class]: Invocation of init method failed; nested exception is org.hibernate.AnnotationException: No identifier specified for entity: com.xxx.domain.Earnings at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1745) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:576) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:498) at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1083) at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:853) at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:546) at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:142) at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775) at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) at org.springframework.boot.SpringApplication.run(SpringApplication.java:316) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260) at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248) at com.xxx.YoufanApplication.main(YoufanApplication.java:21)Caused by: org.hibernate.AnnotationException: No identifier specified for entity: com.xxx.domain.Earnings at org.hibernate.cfg.InheritanceState.determineDefaultAccessType(InheritanceState.java:266) at org.hibernate.cfg.InheritanceState.getElementsToProcess(InheritanceState.java:211) at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:778) at org.hibernate.boot.model.source.internal.annotations.AnnotationMetadataSourceProcessorImpl.processEntityHierarchies(AnnotationMetadataSourceProcessorImpl.java:250) at org.hibernate.boot.model.process.spi.MetadataBuildingProcess$1.processEntityHierarchies(MetadataBuildingProcess.java:231) at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:274) at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:904) at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:935) at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:57) at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:390) at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:377) at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1804) at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1741) … 16 common frames omittedDisconnected from the target VM, address: ‘127.0.0.1:50341’, transport: ‘socket’
Process finished with exit code 1
首先从其中找到核心错误描述：
Invocation of init method failed; nested exception is org.hibernate.AnnotationException: No identifier specified for entity: com.xxx.domain.Earnings
问题原因在实体类com.xxx.domain.Earnings使用javax.persistence.Entity进行注解就会自动进行表的DDL操作
使用hibernate的映射表的时候entity类是必须要主键的，否则就会报出这个异常：No identifier specified for entity
解决方案import javax.persistence.*;
@Entity
public class Earnings {
@Id
@GeneratedValue(strategy = GenerationType.AUTO)
Long id;
// ...
}使用@javax.persistence.Id进行注解后，问题解决。No identifier specified for entity: XXXX错误在运行项目的时候报了下面的错误：
by: org.hibernate.AnnotationException: No identifier specified for entity: com.example1.demo1.Entity.Userat org.hibernate.cfg.InheritanceState.determineDefaultAccessType(InheritanceState.java:266) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]at org.hibernate.cfg.InheritanceState.getElementsToProcess(InheritanceState.java:211) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:731) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]at org.hibernate.boot.model.source.internal.annotations.AnnotationMetadataSourceProcessorImpl.processEntityHierarchies(AnnotationMetadataSourceProcessorImpl.java:249) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]at org.hibernate.boot.model.process.spi.MetadataBuildingProcess$1.processEntityHierarchies(MetadataBuildingProcess.java:222) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:265) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:861) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:888) ~[hibernate-core-5.2.17.Final.jar:5.2.17.Final]
原因及其解决这是因为在实体的getID方法上没有加上此@Id注解，但是检查了一次确实加上了，最后的解决办法如下：
1.在数据库表对应实体（entity.java）的方法:getId()前加上该段文字注解@Id
@GeneratedValue(strategy= GenerationType.AUTO)2.是因为id注解引错了包
错误的包路径：import org.springframework.data.annotation.Id;正确的包路径：import javax.persistence.Id;
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