JPA创建表的问题

Question

实体1继承了另一个实体2,实体2是一个公共的实体,有id,createDate等公共属性,实体1就不需要写这些字段了,但是建表建不了,报错:

Error starting ApplicationContext. To display the conditions report re-run your application with 'debug' enabled.
2018-11-25 13:49:47.332 ERROR 772 --- [           main] o.s.boot.SpringApplication               : Application run failed

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: com.jpa.demo.dto.User
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1745) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:576) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:498) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:320) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:318) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:199) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1083) ~[spring-context-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:853) ~[spring-context-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:546) ~[spring-context-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:140) ~[spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:775) [spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) [spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:316) [spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1260) [spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1248) [spring-boot-2.1.0.RELEASE.jar:2.1.0.RELEASE]
    at com.jpa.JpaDemoApplication.main(JpaDemoApplication.java:13) [classes/:na]
Caused by: org.hibernate.AnnotationException: No identifier specified for entity: com.jpa.demo.dto.User
    at org.hibernate.cfg.InheritanceState.determineDefaultAccessType(InheritanceState.java:266) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]
    at org.hibernate.cfg.InheritanceState.getElementsToProcess(InheritanceState.java:211) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]
    at org.hibernate.cfg.AnnotationBinder.bindClass(AnnotationBinder.java:778) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]
    at org.hibernate.boot.model.source.internal.annotations.AnnotationMetadataSourceProcessorImpl.processEntityHierarchies(AnnotationMetadataSourceProcessorImpl.java:250) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess$1.processEntityHierarchies(MetadataBuildingProcess.java:231) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]
    at org.hibernate.boot.model.process.spi.MetadataBuildingProcess.complete(MetadataBuildingProcess.java:274) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.metadata(EntityManagerFactoryBuilderImpl.java:904) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:935) ~[hibernate-core-5.3.7.Final.jar:5.3.7.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:57) ~[spring-orm-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:390) ~[spring-orm-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:377) ~[spring-orm-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) ~[spring-orm-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1804) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1741) ~[spring-beans-5.1.2.RELEASE.jar:5.1.2.RELEASE]
    ... 16 common frames omitted

实体2:

public class BaseDto implements Serializable {
    private static final long serialVersionUID = -8224576499560872755L;

    /**
     * 主键id
     */
    @Id
    @Column(name = "ID", nullable = false, length = 20, unique = true)
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    /**
     * 创建日期
     */
    @Column(name = "CREATE_DATE", nullable = false)
    private Date createDate;

    /**
     * 修改日期
     */
    @Column(name = "MODIFIED_DATE", nullable = false)
    private Date modifiedDate;

实体1:

@Entity
@Table(name = "USER")
public class User extends BaseDto {
    private static final long serialVersionUID = 7196020041376158025L;

    /**
     * 姓名
     */
    @Column(name = "USER_NAME", nullable = false, length = 20)
    private String userName;

    /**
     * 年龄
     */
    @Column(name = "USER_AGE", length = 3)
    private Integer userAge;

    /**
     * 性别: 1 男, 2 女
     */
    @Column(name = "USER_SEX", length = 1)
    private Integer userSex;

这样没办法创建表么?只能每个实体里都写id,createDate这些重复属性么?

Answer 1

采用继承的方式时父类也要有相应注解并指定继承方法,如

@MappedSuperclass
public class BaseDto implements Serializable {
...