“ManyToMany”关系Spring JPA的问题

【问题标题】：Issue with "ManyToMany" relationship Spring JPA“ManyToMany”关系Spring JPA的问题
【发布时间】：2017-12-12 16:01:32
【问题描述】：

如果这是一个非常愚蠢的问题，我是 Spring 的新手，很抱歉，但我几乎尝试了所有方法。我有用户和角色实体，它们之间有多对多的关系。如果我删除关系，它就可以正常工作，否则我会出错。你能帮帮我吗？

角色类

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;


@Entity
public class Role {

    private Long id;
    private Set<User> users = new HashSet<>();

    public Role(){}
    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }


    @ManyToMany(mappedBy = "roles")
    public Set<User> getUsers() {
        return users;
    }

    public void setUsers(Set<User> users) {
        this.users = users;
    }
}

用户类

import javax.persistence.*;
import java.util.HashSet;
import java.util.Set;


@Entity
public class User {


    private Long id;
    private Set<Role> roles = new HashSet<>();

    public User(){}

    @Id
    @GeneratedValue(strategy = GenerationType.AUTO)
    @Column(name = "id")
    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }


    @ManyToMany
    @JoinTable(name = "user_roles", joinColumns = @JoinColumn(name = "user_id",referencedColumnName = "id"),
            inverseJoinColumns = @JoinColumn(name = "role_id",referencedColumnName = "id"))
    public Set<Role> getRoles() {
        return roles;
    }

    public void setRoles(Set<Role> roles) {
        this.roles = roles;
    }
}

错误

    org.springframework.beans.factory.BeanCreationException: Error creating bean with name 'entityManagerFactory' defined in class path resource [org/springframework/boot/autoconfigure/orm/jpa/HibernateJpaAutoConfiguration.class]: Invocation of init method failed; nested exception is javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1628) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:555) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:483) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:306) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:230) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:302) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:197) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1081) ~[spring-context-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:856) ~[spring-context-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:542) ~[spring-context-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.boot.context.embedded.EmbeddedWebApplicationContext.refresh(EmbeddedWebApplicationContext.java:122) ~[spring-boot-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at org.springframework.boot.SpringApplication.refresh(SpringApplication.java:737) [spring-boot-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at org.springframework.boot.SpringApplication.refreshContext(SpringApplication.java:370) [spring-boot-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:314) [spring-boot-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1162) [spring-boot-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at org.springframework.boot.SpringApplication.run(SpringApplication.java:1151) [spring-boot-1.5.2.RELEASE.jar:1.5.2.RELEASE]
    at com.restaurant.AppConfig.main(AppConfig.java:14) [main/:na]
Caused by: javax.persistence.PersistenceException: [PersistenceUnit: default] Unable to build Hibernate SessionFactory
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.persistenceException(EntityManagerFactoryBuilderImpl.java:954) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:882) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
    at org.springframework.orm.jpa.vendor.SpringHibernateJpaPersistenceProvider.createContainerEntityManagerFactory(SpringHibernateJpaPersistenceProvider.java:60) ~[spring-orm-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:353) ~[spring-orm-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.buildNativeEntityManagerFactory(AbstractEntityManagerFactoryBean.java:370) ~[spring-orm-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:359) ~[spring-orm-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1687) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1624) ~[spring-beans-4.3.7.RELEASE.jar:4.3.7.RELEASE]
    ... 16 common frames omitted
Caused by: org.hibernate.tool.schema.spi.SchemaManagementException: Unable to execute schema management to JDBC target [alter table user_roles add constraint FKrhfovtciq1l558cw6udg0h0d3 foreign key (role_id) references role (id)]
    at org.hibernate.tool.schema.internal.TargetDatabaseImpl.accept(TargetDatabaseImpl.java:59) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.tool.schema.internal.SchemaMigratorImpl.applySqlString(SchemaMigratorImpl.java:431) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.tool.schema.internal.SchemaMigratorImpl.applySqlStrings(SchemaMigratorImpl.java:420) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.tool.schema.internal.SchemaMigratorImpl.applyForeignKeys(SchemaMigratorImpl.java:386) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.tool.schema.internal.SchemaMigratorImpl.doMigrationToTargets(SchemaMigratorImpl.java:214) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.tool.schema.internal.SchemaMigratorImpl.doMigration(SchemaMigratorImpl.java:60) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.tool.hbm2ddl.SchemaUpdate.execute(SchemaUpdate.java:134) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.tool.hbm2ddl.SchemaUpdate.execute(SchemaUpdate.java:101) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.internal.SessionFactoryImpl.<init>(SessionFactoryImpl.java:472) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.boot.internal.SessionFactoryBuilderImpl.build(SessionFactoryBuilderImpl.java:444) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    at org.hibernate.jpa.boot.internal.EntityManagerFactoryBuilderImpl.build(EntityManagerFactoryBuilderImpl.java:879) ~[hibernate-entitymanager-5.0.12.Final.jar:5.0.12.Final]
    ... 22 common frames omitted
Caused by: java.sql.SQLException: Cannot add foreign key constraint
    at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:964) ~[mysql-connector-java-5.1.41.jar:5.1.41]
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3973) ~[mysql-connector-java-5.1.41.jar:5.1.41]
    at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:3909) ~[mysql-connector-java-5.1.41.jar:5.1.41]
    at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:2527) ~[mysql-connector-java-5.1.41.jar:5.1.41]
    at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:2680) ~[mysql-connector-java-5.1.41.jar:5.1.41]
    at com.mysql.jdbc.ConnectionImpl.execSQL(ConnectionImpl.java:2497) ~[mysql-connector-java-5.1.41.jar:5.1.41]
    at com.mysql.jdbc.StatementImpl.executeUpdateInternal(StatementImpl.java:1540) ~[mysql-connector-java-5.1.41.jar:5.1.41]
    at com.mysql.jdbc.StatementImpl.executeLargeUpdate(StatementImpl.java:2595) ~[mysql-connector-java-5.1.41.jar:5.1.41]
    at com.mysql.jdbc.StatementImpl.executeUpdate(StatementImpl.java:1468) ~[mysql-connector-java-5.1.41.jar:5.1.41]
    at org.hibernate.tool.schema.internal.TargetDatabaseImpl.accept(TargetDatabaseImpl.java:56) ~[hibernate-core-5.0.12.Final.jar:5.0.12.Final]
    ... 32 common frames omitted

:bootRun FAILED

【问题讨论】：

  • 您好，您是手动设置数据库，还是让 HIbernate 为您设置？如果你只是在测试，你可以让 HIbernate 删除并创建你的模式，看看here
  • 我使用的是 spring.jpa.hibernate.ddl-auto=update，而 Hibernate 自己创建了表。它适用于首先创建然后更新。但让我感到困惑的是，为什么 update 会创建表。 （顺便说一句，非常感谢！！！）
  • JPA 提供者遵循您运行它的属性。您还没有发布您的 JPA 配置...

标签： java spring hibernate spring-mvc jpa


【解决方案1】：

考虑将其设为单向。在正常情况下，您只需要知道给定用户具有哪些角色。因此，最好的解决方法是从您的角色类中完全删除 getUsers()。

为了让它运行的参考，在关系的两边使用一个连接表。试试这个； 角色.java;

@ManyToMany
@JoinTable(name = "user_roles",
    joinColumns = @JoinColumn(name="role_id"),
    inverseJoinColumns = @JoinColumn(name="user_id"))
public Set<User> getUsers ()

用户.java

@ManyToMany
@JoinTable(name="user_roles",
    joinColumns=@JoinColumn(name="user_id"),
    inverseJoinColumns=@JoinColumn(name="role_id"))
public Set<Role> getRoles() {

[edit] 也可以尝试将其添加到 application.properties 但仅用于测试！

spring.jpa.hibernate.ddl-auto=create-drop

以防万一，从mysql我也试试

drop database your-database-name;
create database your-database-name;

【讨论】：

  • 在这两种情况下，我都会遇到相同的错误。这行可能是我的主要问题“引起：java.sql.SQLException：无法添加外键约束”吗？
  • 我同意，但尚不清楚它为什么会失败。快速提问，您是否在测试之间放弃了表格？认为之前的尝试可能存在一些问题。你在使用默认配置的 Spring boot 吗？
  • 是的，我使用的是默认配置。我没有放弃表格，但在某些时候我放弃了所有表格（我认为它可能会解决我的问题）并再次运行。它没有运行，在数据库中创建了表，但出现了与以前相同的错误。
  • 我在我的答案中添加了一些编辑，您可以尝试。我已经成功地测试了你的课程，所以我认为问题不存在，如果你仍然有问题，我会将我的测试项目上传到 github。
  • 非常感谢您的帮助！一切都已经很好了！
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