引起：java.sql.SQLException：无法添加外键约束

Question

我正在尝试在 Spring Boot 中创建 EShop。我创建了实体、存储库、服务、控制器。添加了所有必要的依赖项。我已经启动了我的应用程序，但它给了我下一个错误。

org.hibernate.tool.schema.spi.CommandAcceptanceException: Error executing DDL "alter table users add constraint FK9dc6h10srm50o3y1d4jn39gxx foreign key (user_id) references cards (id)" via JDBC Statement
    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:67) ~[hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.applySqlString(AbstractSchemaMigrator.java:559) [hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.applySqlStrings(AbstractSchemaMigrator.java:504) [hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.applyForeignKeys(AbstractSchemaMigrator.java:433) [hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.performMigration(AbstractSchemaMigrator.java:249) [hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    at org.hibernate.tool.schema.internal.AbstractSchemaMigrator.doMigration(AbstractSchemaMigrator.java:114) [hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.performDatabaseAction(SchemaManagementToolCoordinator.java:184) [hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    at org.hibernate.tool.schema.spi.SchemaManagementToolCoordinator.process(SchemaManagementToolCoordinator.java:73) [hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:316) [hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:469) [hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:1259) [hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:58) [spring-orm-5.2.10.RELEASE.jar:5.2.10.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:365) [spring-orm-5.2.10.RELEASE.jar:5.2.10.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:391) [spring-orm-5.2.10.RELEASE.jar:5.2.10.RELEASE]
    at java.util.concurrent.FutureTask.run(FutureTask.java:266) ~[na:1.8.0_272]
    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149) ~[na:1.8.0_272]
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624) ~[na:1.8.0_272]
    at java.lang.Thread.run(Thread.java:748) ~[na:1.8.0_272]
Caused by: java.sql.SQLException: Cannot add foreign key constraint
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:129) ~[mysql-connector-java-8.0.22.jar:8.0.22]
    at com.mysql.cj.jdbc.exceptions.SQLError.createSQLException(SQLError.java:97) ~[mysql-connector-java-8.0.22.jar:8.0.22]
    at com.mysql.cj.jdbc.exceptions.SQLExceptionsMapping.translateException(SQLExceptionsMapping.java:122) ~[mysql-connector-java-8.0.22.jar:8.0.22]
    at com.mysql.cj.jdbc.StatementImpl.executeInternal(StatementImpl.java:764) ~[mysql-connector-java-8.0.22.jar:8.0.22]
    at com.mysql.cj.jdbc.StatementImpl.execute(StatementImpl.java:648) ~[mysql-connector-java-8.0.22.jar:8.0.22]
    at com.zaxxer.hikari.pool.ProxyStatement.execute(ProxyStatement.java:95) ~[HikariCP-3.4.5.jar:na]
    at com.zaxxer.hikari.pool.HikariProxyStatement.execute(HikariProxyStatement.java) ~[HikariCP-3.4.5.jar:na]
    at org.hibernate.tool.schema.internal.exec.GenerationTargetToDatabase.accept(GenerationTargetToDatabase.java:54) ~[hibernate-core-5.4.22.Final.jar:5.4.22.Final]
    ... 17 common frames omitted

2020-11-06 21:43:34.914  INFO 7547 --- [         task-1] o.h.e.t.j.p.i.JtaPlatformInitiator       : HHH000490: Using JtaPlatform implementation: [org.hibernate.engine.transaction.jta.platform.internal.NoJtaPlatform]
2020-11-06 21:43:34.929  INFO 7547 --- [         task-1] j.LocalContainerEntityManagerFactoryBean : Initialized JPA EntityManagerFactory for persistence unit 'default'
Caused by: java.sql.SQLException: Cannot add foreign key constraint

有我的用户实体

@Entity
@Table(name = "users")
public class Users {
    @Id
    @GeneratedValue(strategy = GenerationType.IDENTITY)
    private Integer id;

    @Column(name = "name", length = 100)
    private String name;

    @Column(name = "password", length = 100)
    private String password;

    @Column(name = "email", length = 100)
    private String email;

    @OneToMany
    @JoinColumn(name = "card_id", referencedColumnName = "id")
    private List<Card> cardId;
    // contructor, getters and setters

有我的卡实体

@Entity
@Table(name = "cards")
public class Card {
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    private Long id;

    @Column(name = "card_number", length = 100)
    private String cardNumber;

    @OneToMany
    @JoinColumn(name = "user_id", referencedColumnName = "id")
    private List<Users> userId;
    // contructor, getters and setters

有我的 application.properties

spring.datasource.url=jdbc:mysql://${MYSQL_HOST:localhost}:3306/week8
spring.datasource.username=root
spring.datasource.password=admin
spring.jpa.hibernate.ddl-auto=update
spring.jpa.hibernate.naming-strategy=org.hibernate.cfg.ImprovedNamingStrategy
spring.jpa.properties.hibernate.dialect=org.hibernate.dialect.MySQL8Dialect

你能帮我解决这个问题吗，谢谢。

Answer 1

您已经定义了@OneToMany 站点，但我认为@ManyToOne 更重要，因为您将在此处定义列名和外键。类似的东西

@ManyToOne
@JoinColumn(name = "users_id", nullable = false)
private Users users;

看看https://bootify.io - 你可以为你的领域模型创建一个工作示例。