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我有一个问题如何使用@ManyToMany 将项目添加到数据库。

我的第一个实体：

@Entity(name = "groups")
data class Group(
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        val id: Long? = null,
        @Column(name = "name") private var name: String?,
        @ManyToMany(mappedBy = "groups")
        val members: Set<Member> = HashSet()

)

我的第二个实体：

@Entity(name = "members")
data class Member(
        @Id
        @GeneratedValue(strategy = GenerationType.IDENTITY)
        val id: Long? = null,
        @Column(name = "name") val name: String,
        @ManyToMany
        @JoinTable(name = "groups_members",
                joinColumns = [JoinColumn(name = "member_id")],
                inverseJoinColumns = [JoinColumn(name = "group_id")])
        val groups: Set<Group> = HashSet()
)

代码如：

member.groups.add(group)

不工作我也使用了 List 和 ArrayList，结果是一样的。

日志

    Wed May 20 10:42:33 CEST 2020
    There was an unexpected error (type=Internal Server Error, status=500).
    org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.example.demo.data.Group; nested exception is java.lang.IllegalStateException: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.example.demo.data.Group
    org.springframework.dao.InvalidDataAccessApiUsageException: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.example.demo.data.Group; nested exception is java.lang.IllegalStateException: org.hibernate.TransientObjectException: object references an unsaved transient instance - save the transient instance before flushing: com.example.demo.data.Group
        at org.springframework.orm.jpa.EntityManagerFactoryUtils.convertJpaAccessExceptionIfPossible(EntityManagerFactoryUtils.java:371)
        at org.springframework.orm.jpa.vendor.HibernateJpaDialect.translateExceptionIfPossible(HibernateJpaDialect.java:257)
        at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:538)
        at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:743)
        at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:711)
        at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:631)
        at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:385)
        at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:118)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
        at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:139)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
        at org.springframework.data.jpa.repository.support.CrudMethodMetadataPostProcessor$CrudMethodMetadataPopulatingMethodInterceptor.invoke(CrudMethodMetadataPostProcessor.java:178)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
        at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:95)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
        at org.springframework.data.repository.core.support.MethodInvocationValidator.invoke(MethodInvocationValidator.java:99)
        at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:186)
        at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:212)
        at com.sun.proxy.$Proxy98.save(Unknown Source)
... 241 more
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0 回答 0