为什么我得到一个主键违反的@OneTo许多属性？

Question

我有一个实体：

@Entity
public class Student {

    @GeneratedValue(strategy = GenerationType.AUTO)
    @Id
    private long id;

    @OneToMany
    private Set<Course> courses;
}

当我试图持久化这种类型的第一个实体时，它工作正常，但当我试图用与已存储实体相同的课程保存一个新学生时，它失败了。以下是错误：

insert into student_courses (student, courses) values (?, ?) [23505-172]]; nested exception is org.hibernate.exception.ConstraintViolationException: could not execute statement] with root cause

org.h2.jdbc.JdbcSQLException: Unique index or primary key violation: "UK_1DBE7B943AC44E1B841DA2688EB_INDEX_5 ON PUBLIC.STUDENT_COURSES(COURSES)"; SQL statement:
insert into student_courses (student, courses) values (?, ?) [23505-172]
    at org.h2.message.DbException.getJdbcSQLException(DbException.java:329)
    at org.h2.message.DbException.get(DbException.java:169)
    at org.h2.message.DbException.get(DbException.java:146)
    at org.h2.index.BaseIndex.getDuplicateKeyException(BaseIndex.java:83)
    at org.h2.index.TreeIndex.add(TreeIndex.java:65)
    at org.h2.table.RegularTable.addRow(RegularTable.java:124)
    at org.h2.command.dml.Insert.insertRows(Insert.java:126)
    at org.h2.command.dml.Insert.update(Insert.java:86)
    at org.h2.command.CommandContainer.update(CommandContainer.java:79)
    at org.h2.command.Command.executeUpdate(Command.java:235)
    at org.h2.jdbc.JdbcPreparedStatement.executeUpdateInternal(JdbcPreparedStatement.java:154)
    at org.h2.jdbc.JdbcPreparedStatement.executeUpdate(JdbcPreparedStatement.java:140)
    at org.hibernate.engine.jdbc.internal.ResultSetReturnImpl.executeUpdate(ResultSetReturnImpl.java:133)
    at org.hibernate.engine.jdbc.batch.internal.NonBatchingBatch.addToBatch(NonBatchingBatch.java:58)
    at org.hibernate.persister.collection.AbstractCollectionPersister.recreate(AbstractCollectionPersister.java:1256)
    at org.hibernate.action.internal.CollectionRecreateAction.execute(CollectionRecreateAction.java:58)
    at org.hibernate.engine.spi.ActionQueue.execute(ActionQueue.java:364)
    at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:356)
    at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:281)
    at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:328)
    at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:52)
    at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1234)
    at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:404)
    at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.beforeTransactionCommit(JdbcTransaction.java:101)
    at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.commit(AbstractTransactionImpl.java:175)
    at org.hibernate.ejb.TransactionImpl.commit(TransactionImpl.java:75)
    at org.springframework.orm.jpa.JpaTransactionManager.doCommit(JpaTransactionManager.java:515)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:757)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:726)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:478)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:272)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:95)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.dao.support.PersistenceExceptionTranslationInterceptor.invoke(PersistenceExceptionTranslationInterceptor.java:158)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.data.jpa.repository.support.LockModeRepositoryPostProcessor$LockModePopulatingMethodIntercceptor.invoke(LockModeRepositoryPostProcessor.java:92)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:92)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
    at com.sun.proxy.$Proxy45.save(Unknown Source)
    at students.StudentController.createRandomShiur(ShiurimController.java:66)
    at shiurim.StudentController.getStudents(StudentController.java:26)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at org.springframework.web.method.support.InvocableHandlerMethod.invoke(InvocableHandlerMethod.java:220)
    at org.springframework.web.method.support.InvocableHandlerMethod.invokeForRequest(InvocableHandlerMethod.java:133)
    at org.springframework.web.servlet.mvc.method.annotation.ServletInvocableHandlerMethod.invokeAndHandle(ServletInvocableHandlerMethod.java:104)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.invokeHandleMethod(RequestMappingHandlerAdapter.java:746)
    at org.springframework.web.servlet.mvc.method.annotation.RequestMappingHandlerAdapter.handleInternal(RequestMappingHandlerAdapter.java:687)
    at org.springframework.web.servlet.mvc.method.AbstractHandlerMethodAdapter.handle(AbstractHandlerMethodAdapter.java:83)
    at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:925)
    at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:856)
    at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:946)
    at org.springframework.web.servlet.FrameworkServlet.doGet(FrameworkServlet.java:837)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:621)
    at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:822)
    at javax.servlet.http.HttpServlet.service(HttpServlet.java:728)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.springframework.web.filter.HiddenHttpMethodFilter.doFilterInternal(HiddenHttpMethodFilter.java:77)
    at org.springframework.web.filter.OncePerRequestFilter.doFilter(OncePerRequestFilter.java:108)
    at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:243)
    at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)
    at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:222)
    at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)
    at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:502)
    at org.apache.catalina.valves.RemoteIpValve.invoke(RemoteIpValve.java:680)
    at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:171)
    at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:99)
    at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)
    at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:408)
    at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1023)
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:589)
    at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.run(NioEndpoint.java:1686)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
    at java.lang.Thread.run(Thread.java:695)

我正在使用Spring数据JPA，以Hibernate和H2作为数据库。

应用程序创建了自己的数据库表：

HibernateJpaVendorAdapter hibernateJpaVendorAdapter = new HibernateJpaVendorAdapter();
hibernateJpaVendorAdapter.setShowSql(false);
hibernateJpaVendorAdapter.setGenerateDdl(true);
hibernateJpaVendorAdapter.setDatabase(Database.H2);

那么，为什么会有一个唯一的约束？

更新：

我看到Hibernate添加了约束：

Hibernate: alter table student_courses add constraint UK_a8c48f36df374f1293c46699c83 unique (courses)

我怎么告诉Hibernate不要创建它？

谢谢

Answer 1

很可能您在实际具有@ManyTo多国关系时设置了@OneTo多国。

假设课程没有自动生成的ID，那么第二个学生添加同名课程时就会出现问题。
由于是一对多的关系，因此将使用相同的唯一受限ID创建新课程

Answer 2

您必须使用GenerationType。表，而不是GenerationType。自动。这样，jpa使用序列表进行id分配，您可能永远不需要生成序列或自动增量值或降低可移植性的触发器。

Answer 3

由于冲突发生在STUDENT_COURSES表中，您似乎试图将相同的关系持久化两次。您映射了一个Set，它向Hibernate发出信号，表明这些关系必须发生不超过一次。检查生成的DDLCOURSE_ID、STUDENT_ID）上的唯一索引。

原因可能是您的程序逻辑中存在缺陷（例如，在将与课程相关的字段添加到集合后修改这些字段，或者是您的课程实体中存在故障。

如果学生可以参加一门课程不止一次（例如第一次失败），你必须自己决定（你在现实世界中的客户，因为这是一个商业决定）。