hibernate - 如何从 JoinTable 加载一组字符串？

Question

我使用的是 MySQL 5.5、JPA 2.0 和 Hibernate 4.1.0.Final。我的实体中有这个字段......

@Entity
@Table(name = "teacher",
    uniqueConstraints = {…}
)
public class TrainingSessionTeacher implements Serializable 
{
    …
    @ManyToMany
    @JoinTable(name = "teacher_subj", joinColumns = { @JoinColumn(name = "EACHER_ID") }, inverseJoinColumns = { @JoinColumn(name = "SUBJECT") })
    private Set<String> subjects;

有问题的连接表具有以下结构:

| Field                       | Type        | Null | Key | Default | Extra |
+-----------------------------+-------------+------+-----+---------+-------+
| ID                          | varchar(32) | NO   | PRI | NULL    |       |
| TEACHER_ID                  | varchar(32) | NO   | MUL | NULL    |       |
| SUBJECT                     | varchar(32) | NO   |     | NULL    |       |

但是，在加载我的应用程序上下文时，出现异常“org.hibernate.AnnotationException: Use of @OneToMany or @ManyToMany 针对未映射的类:org.mainco.subco.pd.domain.TrainingSessionTeacher.subjects[java.lang.String ]”。有没有办法可以在我的实体中映射一组字符串？我希望不必为“teacher_subj”类创建单独的实体。

完整的堆栈跟踪如下:

Caused by: org.hibernate.AnnotationException: Use of @OneToMany or @ManyToMany targeting an unmapped class: org.mainco.subco.pd.domain.TrainingSessionTeacher.subjects[java.lang.String]
    at org.hibernate.cfg.annotations.CollectionBinder.bindManyToManySecondPass(CollectionBinder.java:1160)
    at org.hibernate.cfg.annotations.CollectionBinder.bindStarToManySecondPass(CollectionBinder.java:691)
    at org.hibernate.cfg.annotations.CollectionBinder$1.secondPass(CollectionBinder.java:626)
    at org.hibernate.cfg.CollectionSecondPass.doSecondPass(CollectionSecondPass.java:66)
    at org.hibernate.cfg.Configuration.originalSecondPassCompile(Configuration.java:1587)
    at org.hibernate.cfg.Configuration.secondPassCompile(Configuration.java:1362)
    at org.hibernate.cfg.Configuration.buildSessionFactory(Configuration.java:1727)
    at org.hibernate.ejb.EntityManagerFactoryImpl.<init>(EntityManagerFactoryImpl.java:88)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:904)
    at org.hibernate.ejb.Ejb3Configuration.buildEntityManagerFactory(Ejb3Configuration.java:889)
    at org.hibernate.ejb.HibernatePersistence.createContainerEntityManagerFactory(HibernatePersistence.java:73)
    at org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean.createNativeEntityManagerFactory(LocalContainerEntityManagerFactoryBean.java:287)
    at org.springframework.orm.jpa.AbstractEntityManagerFactoryBean.afterPropertiesSet(AbstractEntityManagerFactoryBean.java:310)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.invokeInitMethods(AbstractAutowireCapableBeanFactory.java:1514)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.initializeBean(AbstractAutowireCapableBeanFactory.java:1452)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.doCreateBean(AbstractAutowireCapableBeanFactory.java:519)
    at org.springframework.beans.factory.support.AbstractAutowireCapableBeanFactory.createBean(AbstractAutowireCapableBeanFactory.java:456)
    at org.springframework.beans.factory.support.AbstractBeanFactory$1.getObject(AbstractBeanFactory.java:294)
    at org.springframework.beans.factory.support.DefaultSingletonBeanRegistry.getSingleton(DefaultSingletonBeanRegistry.java:225)
    at org.springframework.beans.factory.support.AbstractBeanFactory.doGetBean(AbstractBeanFactory.java:291)
    at org.springframework.beans.factory.support.AbstractBeanFactory.getBean(AbstractBeanFactory.java:193)
    at org.springframework.context.support.AbstractApplicationContext.getBean(AbstractApplicationContext.java:1105)
    at org.springframework.context.support.AbstractApplicationContext.finishBeanFactoryInitialization(AbstractApplicationContext.java:915)
    at org.springframework.context.support.AbstractApplicationContext.refresh(AbstractApplicationContext.java:472)
    at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:103)
    at org.springframework.test.context.support.AbstractGenericContextLoader.loadContext(AbstractGenericContextLoader.java:1)
    at org.springframework.test.context.support.DelegatingSmartContextLoader.loadContext(DelegatingSmartContextLoader.java:228)
    at org.springframework.test.context.TestContext.loadApplicationContext(TestContext.java:124)
    at org.springframework.test.context.TestContext.getApplicationContext(TestContext.java:148)
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.injectDependencies(DependencyInjectionTestExecutionListener.java:109)
    at org.springframework.test.context.support.DependencyInjectionTestExecutionListener.prepareTestInstance(DependencyInjectionTestExecutionListener.java:75)
    at org.springframework.test.context.TestContextManager.prepareTestInstance(TestContextManager.java:321)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.createTest(SpringJUnit4ClassRunner.java:211)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner$1.runReflectiveCall(SpringJUnit4ClassRunner.java:288)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.methodBlock(SpringJUnit4ClassRunner.java:290)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:231)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:49)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:71)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:174)
    at org.apache.maven.surefire.junit4.JUnit4Provider.execute(JUnit4Provider.java:264)
    at org.apache.maven.surefire.junit4.JUnit4Provider.executeTestSet(JUnit4Provider.java:153)
    at org.apache.maven.surefire.junit4.JUnit4Provider.invoke(JUnit4Provider.java:124)
    at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:200)
    at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:153)
    at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:103)

感谢您的帮助，-戴夫

编辑:使用元素集合，我将我的字段更改为

@ElementCollection(fetch = FetchType.EAGER)
@CollectionTable(name = "teacher_subj", joinColumns = {@JoinColumn(name="TEACHER_ID")})
private Set<String> subject;

但是当我使用实体类的“setSubject”方法设置这个值时，没有任何东西被持久化到数据库中。我是否需要添加一些其他注释才能让 Hibernate 为我的 Teacher_subj 生成 SQL 以正确保存到数据库？

Answer 1

使用 @ElementCollection而不是 @ManyToMany , 因为 @ManyToMany在实体之间，和一个 String不是 Entity .另外替换 @JoinTable与 @CollectionTable(name="teacher_subj", joinColumns=@JoinColumn(name="TEACHER_ID"))