"org.hibernate.AnnotationException: No identifier specified for entity"异常分析

环境设置

Spring Data JPA， Hibernate
Spring Boot 2.1.13.RELEASE

异常信息：

异常信息如下：

org.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: org.spb.data.dao.entity.UserEntity
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1771) ~[spring-beans-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:593) ~[spring-beans-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:515) ~[spring-beans-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1105) ~[spring-context-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:867) ~[spring-context-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:549) ~[spring-context-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.1.13.RELEASE.jar:2.1.13.RELEASE]
	at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:744) [spring-boot-2.1.13.RELEASE.jar:2.1.13.RELEASE]
	at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:391) [spring-boot-2.1.13.RELEASE.jar:2.1.13.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:312) [spring-boot-2.1.13.RELEASE.jar:2.1.13.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) [spring-boot-2.1.13.RELEASE.jar:2.1.13.RELEASE]
	at org.springframework.boot.SpringApplication.run(SpringApplication.java:1204) [spring-boot-2.1.13.RELEASE.jar:2.1.13.RELEASE]
	at org.spb.data.UserLoginApplication.main(UserLoginApplication.java:14) [classes/:na]
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) ~[na:1.8.0_192]
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) ~[na:1.8.0_192]
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) ~[na:1.8.0_192]
	at java.lang.reflect.Method.invoke(Method.java:498) ~[na:1.8.0_192]
	at org.springframework.boot.devtools.restart.RestartLauncher.run(RestartLauncher.java:49) [spring-boot-devtools-2.1.13.RELEASE.jar:2.1.13.RELEASE]
Caused by: org.hibernate.AnnotationException: No identifier specified for entity: org.spb.data.dao.entity.UserEntity
	at org.hibernate.cfg.InheritanceState.determineDefaultAccessType(InheritanceState.java:266) ~[hibernate-core-5.3.15.Final.jar:5.3.15.Final]
	at org.hibernate.cfg.InheritanceState.getElementsToProcess(InheritanceState.java:211) ~[hibernate-core-5.3.15.Final.jar:5.3.15.Final]
	at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:775) ~[hibernate-core-5.3.15.Final.jar:5.3.15.Final]
	at org.hibernate.boot.model.source.internal.annotations.AnnotationMetadataSourceProcessorImpl.processEntityHierarchies(AnnotationMetadataSourceProcessorImpl.java:250) ~[hibernate-core-5.3.15.Final.jar:5.3.15.Final]
	at org.hibernate.boot.model.process.spi.MetadataBuildingProcess$1.processEntityHierarchies(MetadataBuildingProcess.java:231) ~[hibernate-core-5.3.15.Final.jar:5.3.15.Final]
	at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:274) ~[hibernate-core-5.3.15.Final.jar:5.3.15.Final]
	at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:1215) ~[hibernate-core-5.3.15.Final.jar:5.3.15.Final]
	at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1246) ~[hibernate-core-5.3.15.Final.jar:5.3.15.Final]
	at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) ~[spring-orm-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:391) ~[spring-orm-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:378) ~[spring-orm-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) ~[spring-orm-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1830) ~[spring-beans-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1767) ~[spring-beans-5.1.14.RELEASE.jar:5.1.14.RELEASE]
	... 21 common frames omitted

问题分析

从异常信息分析可知，缺乏唯一标识，应该主键之类的缺失。
UserEntity.java定义如下：

@Entity
@Table(name="auth_user")
@Data@EqualsAndHashCode(callSuper=true)
public class UserEntity extends BaseEntity {
	private static final long serialVersionUID = 8413191100461926897L;

	@Column
	private String name;
	
	@Column
	private String password;
	
	//Role List
	@Column
	private List<String> roles;
}

BaseEntity.java定义如下：

package org.spb.data.dao.base;

import java.io.Serializable;
import java.time.LocalDateTime;
import java.util.Date;

import javax.persistence.Column;
import javax.persistence.EntityListeners;
import javax.persistence.GeneratedValue;
import javax.persistence.Id;
import lombok.Data;

@Data
public abstract class BaseEntity implements Serializable {
	private static final long serialVersionUID = -5777041700442398469L;

	@Id
	@GeneratedValue
	private Long id;
	
    //..............
    //乐观锁
    @Version
    private Long version;
}

在BaseEntity明明定义了@Id主键的，为什么不启作用呢？那问题应该就在这里。
经过一份查找之后得知，这里需要增加一个将当前类标注为：

@MappedSuperclass

问题解决

将@MappedSuperclass放置到BaseEntity之上即可解决问题。
其在官方文档中定义如下：

Designates a class whose mapping information is applied to the entities that inherit from it. A mapped superclass  has no separate table defined for it.  
A class designated with the <code>MappedSuperclass</code>  annotation can be mapped in the same way as an entity except that the mappings will apply only to its subclasses since no table  exists for the mapped superclass itself. When applied to the  subclasses the inherited mappings will apply in the context  of the subclass tables.

其核心意思是：其做基本，无实际的表与之对应。