java - hibernate : Foreign key constraint violation problem

Question

我的代码中有一个 com.mysql.jdbc.exceptions.MySQLIntegrityConstraintViolationException(使用 Hibernate 和 Spring)，我不知道为什么。 我的实体是 Corpus 和 Semspace，并且在我的 hibernate 映射配置中定义了从 Semspace 到 Corpus 的多对一关系:

<class name="xxx.entities.Semspace" table="Semspace" lazy="false" batch-size="30">
    <id name="id" column="idSemspace" type="java.lang.Integer" unsaved-value="null">
        <generator class="identity"/>
    </id>
    <property name="name" column="name" type="java.lang.String" not-null="true" unique="true" />
    <many-to-one name="corpus" class="xxx.entities.Corpus" column="idCorpus"
                insert="false" update="false" />
    [...]
</class>
<class name="xxx.entities.Corpus" table="Corpus" lazy="false" batch-size="30">
    <id name="id" column="idCorpus" type="java.lang.Integer" unsaved-value="null">
        <generator class="identity"/>
    </id>
    <property name="name" column="name" type="java.lang.String" not-null="true" unique="true" />
</class>

产生异常的 Java 代码是:

Corpus corpus = Spring.getCorpusDAO().getCorpusById(corpusId);
Semspace semspace = new Semspace();
semspace.setCorpus(corpus);
semspace.setName(name);
Spring.getSemspaceDAO().save(semspace);

我检查了一下语料库变量不为空(所以它在数据库中，用 DAO 检索) 完整的异常(exception)是:

com.mysql.jdbc.exceptions.MySQLIntegrityConstraintViolationException: Cannot add or update a child row: a foreign key constraint fails (`xxx/Semspace`, CONSTRAINT `FK4D6019AB6556109` FOREIGN KEY (`idCorpus`) REFERENCES `Corpus` (`idCorpus`))
at com.mysql.jdbc.SQLError.createSQLException(SQLError.java:931)
at com.mysql.jdbc.MysqlIO.checkErrorPacket(MysqlIO.java:2941)
at com.mysql.jdbc.MysqlIO.sendCommand(MysqlIO.java:1623)
at com.mysql.jdbc.MysqlIO.sqlQueryDirect(MysqlIO.java:1715)
at com.mysql.jdbc.Connection.execSQL(Connection.java:3249)
at com.mysql.jdbc.PreparedStatement.executeInternal(PreparedStatement.java:1268)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1541)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1455)
at com.mysql.jdbc.PreparedStatement.executeUpdate(PreparedStatement.java:1440)
at org.apache.commons.dbcp.DelegatingPreparedStatement.executeUpdate(DelegatingPreparedStatement.java:102)
at org.hibernate.id.IdentityGenerator$GetGeneratedKeysDelegate.executeAndExtract(IdentityGenerator.java:73)
at org.hibernate.id.insert.AbstractReturningDelegate.performInsert(AbstractReturningDelegate.java:33)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2158)
at org.hibernate.persister.entity.AbstractEntityPersister.insert(AbstractEntityPersister.java:2638)
at org.hibernate.action.EntityIdentityInsertAction.execute(EntityIdentityInsertAction.java:48)
at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:250)
at org.hibernate.event.def.AbstractSaveEventListener.performSaveOrReplicate(AbstractSaveEventListener.java:298)
at org.hibernate.event.def.AbstractSaveEventListener.performSave(AbstractSaveEventListener.java:181)
at org.hibernate.event.def.AbstractSaveEventListener.saveWithGeneratedId(AbstractSaveEventListener.java:107)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.saveWithGeneratedOrRequestedId(DefaultSaveOrUpdateEventListener.java:187)
at org.hibernate.event.def.DefaultSaveEventListener.saveWithGeneratedOrRequestedId(DefaultSaveEventListener.java:33)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.entityIsTransient(DefaultSaveOrUpdateEventListener.java:172)
at org.hibernate.event.def.DefaultSaveEventListener.performSaveOrUpdate(DefaultSaveEventListener.java:27)
at org.hibernate.event.def.DefaultSaveOrUpdateEventListener.onSaveOrUpdate(DefaultSaveOrUpdateEventListener.java:70)
at org.hibernate.impl.SessionImpl.fireSave(SessionImpl.java:535)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:523)
at org.hibernate.impl.SessionImpl.save(SessionImpl.java:519)
at org.springframework.orm.hibernate3.HibernateTemplate$12.doInHibernate(HibernateTemplate.java:642)
at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:373)
at org.springframework.orm.hibernate3.HibernateTemplate.save(HibernateTemplate.java:639)
at xxx.dao.impl.AbstractDAO.save(AbstractDAO.java:26)
at org.apache.jsp.functions.semspaceManagement_jsp._jspService(semspaceManagement_jsp.java:218)
[...]

外键约束已由 hibernate 创建(并添加到数据库中)，我看不出哪里可以违反约束。该表是 innodb，我试图删除所有表并重新创建它，问题仍然存在......

编辑:好吧，我想我有一个开始的答案......我将 hibernate 的日志级别更改为 DEBUG 并且在它崩溃之前我有以下日志

insert into Semspace (name, [...]) values (?, [...])

所以看起来它不会尝试插入 idCorpus，因为它不是空的，所以它使用默认值“0”，它不引用语料库表中的现有条目...

Answer 1

我总是对关联映射感到困惑。查看所需的关联以及用于创建关联的 hibernate 映射配置。

http://docs.jboss.org/hibernate/core/3.5/reference/en/html/associations.html

是一本很棒的协会食谱书。