在 JPA 中将单个实体映射到多个表：错误

【问题标题】：Mapping Single Entity to Multiple Tables in JPA: Error在 JPA 中将单个实体映射到多个表：错误
【发布时间】：2020-10-28 05:46:26
【问题描述】：

我正在开发 Java Spring Boot Web 应用程序，但在将实体映射到多个表时遇到问题。手头的两个表是“Profile”和“Users”。用户具有属性“电子邮件”，我希望能够将其放入个人资料中。为此，我在创建配置文件表时使用@SecondaryTable 注释，以便将用户表与其连接。下面是 Profile 实体：

@Entity
@Table(name="Profile")
@SecondaryTable(name="Users", pkJoinColumns=@PrimaryKeyJoinColumn(name="userId"))
public class Profile {

    @Id
    @GeneratedValue(strategy=GenerationType.AUTO)
    @Column(name="profileId")
    private long profileId;

    @OneToOne(targetEntity=SiteUser.class)
    @JoinColumn(name="user_id", nullable=false)
    private SiteUser user;
    
    @Column(name="about", length=1000)
    @Size(max=1000, message="{edit.profile.about.size}")
    private String about;
    
    @Column(name="email", table="Users")
    private String email;

    ...
}

然后这里是用户实体：

@Entity
@Table(name="Users")
@PasswordMatch(message="{register.repeatPassword.mismatch}")
public class SiteUser {
    
    @Id
    @Column(name="userId")
    @GeneratedValue(strategy=GenerationType.AUTO)
    private Long userId;

    @Column(name="email", unique=true)
    @Email(message="{register.email.invalid}")
    @NotBlank(message="{register.email.invalid}")
    private String email;
    ...
}

我得到的错误如下：

org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "alter table users add constraint FKce1xk9c9bdk7obdg7sva65g88 foreign key (user_id) references profile (profile_id)" via JDBC Statement
    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:67) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.applySqlString(AbstractSchemaMigrator.java:559) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.applySqlStrings(AbstractSchemaMigrator.java:504) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.applyForeignKeys(AbstractSchemaMigrator.java:433) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.performMigration(AbstractSchemaMigrator.java:249) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.doMigration(AbstractSchemaMigrator.java:114) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:184) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:73) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:320) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:462) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1237) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) ~[spring-orm-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) ~[spring-orm-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:391) ~[spring-orm-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:378) ~[spring-orm-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.afterPropertiesSet(LocalContainerEntityManagerFactoryBean.java:341) ~[spring-orm-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1855) ~[spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1792) ~[spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:595) ~[spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:517) ~[spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.lambda$doGetBean$0(AbstractBeanFactory.java:323) ~[spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:222) ~[spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:321) ~[spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:202) ~[spring-beans-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1108) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:868) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:550) ~[spring-context-5.2.2.RELEASE.jar:5.2.2.RELEASE]
    at org.springframework.boot.web.servlet.context.ServletWebServerApplicationContext.refresh(ServletWebServerApplicationContext.java:141) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:747) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:397) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:315) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1226) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1215) ~[spring-boot-2.2.2.RELEASE.jar:2.2.2.RELEASE]
    at bcoreHW.App.main(App.java:27) ~[classes/:na]
Caused by: java.sql.SQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`dbName`.`#sql-8c_2b2`, CONSTRAINT `FKce1xk9c9bdk7obdg7sva65g88` FOREIGN KEY (`user_id`) REFERENCES `profile` (`profile_id`))
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:117) ~[mysql-connector-java-8.0.18.jar:8.0.18]
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.18.jar:8.0.18]
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.18.jar:8.0.18]
    at com.mysql.cj.jdbc.StatementImpl.executeInternal(StatementImpl.java:764) ~[mysql-connector-java-8.0.18.jar:8.0.18]
    at com.mysql.cj.jdbc.StatementImpl.execute(StatementImpl.java:648) ~[mysql-connector-java-8.0.18.jar:8.0.18]
    at com.zaxxer.hikari.pool.ProxyStatement.execute(ProxyStatement.java:95) ~[HikariCP-3.4.1.jar:na]
    at com.zaxxer.hikari.pool.HikariProxyStatement.execute(HikariProxyStatement.java) ~[HikariCP-3.4.1.jar:na]
    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:54) ~[hibernate-core-5.4.9.Final.jar:5.4.9.Final]
    ... 33 common frames omitted

我四处搜索并尝试添加spring.jpa.hibernate.ddl-auto=update，但这没有任何作用。任何关于我为什么会收到此错误的想法将不胜感激。

【问题讨论】：

    标签： java spring-boot spring-data-jpa modelattribute secondary-table


    【解决方案1】：

    您实际上在两个实体中使用表Users - 作为实体Profile 的一部分和作为实体SiteUser。这是非常有问题的设计。这尤其意味着当您尝试删除SiteUser 的条目时，它可能是某个条目Profile 的一部分，因此您可能希望删除Profile 的一部分。外键保护这种删除。

    我建议你检查一下你真正需要什么。

    1. 您想拥有一个存储在 2 个表中的实体吗？然后删除实体SiteUser，只使用实体Profile。
    2. 您想在Profile 和Users 这两个表中有相对独立的条目吗？然后不要为单个实体使用 2 个表。相反，对于实体 Profile 使用单个表 Profile，对于与 User 实体的关系使用关系，具体取决于您的目标 @OneToOne 或 @OneToMany。

    【讨论】：

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