我想使用hibernate中存在的乐观锁定功能。为此，我按如下方式为我的表配置了映射：
<hibernate-mapping package="org.example.dao.entity">
<class name="org.example.dao.entity.EmployeeEntity" table="employee" dynamic-update="false">
<id name="id" column="employee_id">
<generator class="identity"/>
</id>
<version name="version" column="version" type="java.lang.Integer" generated="always"/>
<property name="firstName" column="first_name" type="java.lang.String"/>
<set name="projects" table="employee_to_project" inverse="true">
<key column="employee_id"/>
<many-to-many column="project_id" class="ProjectEntity"/>
</set>
</class>
</hibernate-mapping>
我使用了generate =＆＃34;总是＆＃34;并在db中创建了以下触发器：
CREATE OR REPLACE FUNCTION public.tab_employee_update_version()
RETURNS trigger
LANGUAGE plpgsql
AS
$body$
BEGIN
NEW.version = coalesce(OLD.version,0) + 1;
RETURN NEW;
END;
$body$
/
然后我运行以下代码：
public static void main(String[] args) {
ApplicationContext ctx = new ClassPathXmlApplicationContext("context.xml");
final EmployeeService employeeService = ctx.getBean("employeeService", EmployeeService.class);
// SELECT
Employee employee = employeeService.getById(1L);
// UPDATE
employeeService.update(employee);
}
并获取HibernateOptimisticLockingFailureException，尽管员工记录未被其他事务同时更改：
Exception in thread "main" org.springframework.orm.hibernate4.HibernateOptimisticLockingFailureException: Object of class [org.example.dao.entity.EmployeeEntity] with identifier [1]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect) : [org.example.dao.entity.EmployeeEntity#1]
at org.springframework.orm.hibernate4.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:202)
at org.springframework.orm.hibernate4.HibernateTransactionManager.convertHibernateAccessException(HibernateTransactionManager.java:730)
at org.springframework.orm.hibernate4.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:592)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:761)
at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:730)
at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:485)
at org.springframework.transaction.interceptor.TransactionAspectSupport.invokeWithinTransaction(TransactionAspectSupport.java:291)
at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:96)
at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:179)
at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:207)
at com.sun.proxy.$Proxy15.update(Unknown Source)
at org.example.AppMain.main(AppMain.java:25)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:134)
Caused by: org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect) : [org.example.dao.entity.EmployeeEntity#1]
at org.hibernate.persister.entity.AbstractEntityPersister.check(AbstractEntityPersister.java:2541)
at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:3285)
at org.hibernate.persister.entity.AbstractEntityPersister.updateOrInsert(AbstractEntityPersister.java:3183)
at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:3525)
at org.hibernate.action.internal.EntityUpdateAction.execute(EntityUpdateAction.java:159)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:465)
at org.hibernate.engine.spi.ActionQueue.executeActions(ActionQueue.java:351)
at org.hibernate.event.internal.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:350)
at org.hibernate.event.internal.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:56)
at org.hibernate.internal.SessionImpl.flush(SessionImpl.java:1258)
at org.hibernate.internal.SessionImpl.managedFlush(SessionImpl.java:425)
at org.hibernate.engine.transaction.internal.jdbc.JdbcTransaction.beforeTransactionCommit(JdbcTransaction.java:101)
at org.hibernate.engine.transaction.spi.AbstractTransactionImpl.commit(AbstractTransactionImpl.java:177)
at org.springframework.orm.hibernate4.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:584)
... 14 more
事务边界在服务级别（EmployeeService类标记有@Transactional注释）。
我调试了代码并发现，hibernate会在更新期间自动增加版本：
Hibernate: select employeeen0_.employee_id as employee1_1_0_, employeeen0_.version as version2_1_0_, employeeen0_.age as age3_1_0_, employeeen0_.first_name as first_na4_1_0_, employeeen0_.last_name as last_nam5_1_0_ from employee employeeen0_ where employeeen0_.employee_id=?
10:36:46,258 TRACE main sql.BasicBinder:81 - binding parameter [1] as [BIGINT] - [1]
10:36:46,270 TRACE main sql.BasicExtractor:78 - extracted value ([version2_1_0_] : [INTEGER]) - [57]
10:36:46,270 TRACE main sql.BasicExtractor:78 - extracted value ([age3_1_0_] : [INTEGER]) - [0]
10:36:46,271 TRACE main sql.BasicExtractor:78 - extracted value ([first_na4_1_0_] : [VARCHAR]) - [Bogumil]
10:36:46,271 TRACE main sql.BasicExtractor:78 - extracted value ([last_nam5_1_0_] : [VARCHAR]) - [Bednarek]
10:36:46,280 TRACE main type.CollectionType:783 - Created collection wrapper: [org.example.dao.entity.EmployeeEntity.projects#1]
Hibernate: select projects0_.employee_id as employee1_1_0_, projects0_.project_id as project_2_2_0_, projectent1_.project_id as project_1_3_1_, projectent1_.name as name2_3_1_ from employee_to_project projects0_ inner join project projectent1_ on projects0_.project_id=projectent1_.project_id where projects0_.employee_id=?
10:36:46,394 TRACE main sql.BasicBinder:81 - binding parameter [1] as [BIGINT] - [1]
10:36:46,397 TRACE main sql.BasicExtractor:78 - extracted value ([project_1_3_1_] : [BIGINT]) - [1]
10:36:46,397 TRACE main sql.BasicExtractor:78 - extracted value ([name2_3_1_] : [VARCHAR]) - [Project1]
10:36:46,398 TRACE main sql.BasicExtractor:78 - extracted value ([employee1_1_0_] : [BIGINT]) - [1]
10:36:46,398 TRACE main sql.BasicExtractor:78 - extracted value ([project_2_2_0_] : [BIGINT]) - [1]
10:36:46,399 TRACE main sql.BasicExtractor:78 - extracted value ([project_1_3_1_] : [BIGINT]) - [2]
10:36:46,399 TRACE main sql.BasicExtractor:78 - extracted value ([name2_3_1_] : [VARCHAR]) - [Project2]
10:36:46,400 TRACE main sql.BasicExtractor:78 - extracted value ([employee1_1_0_] : [BIGINT]) - [1]
10:36:46,400 TRACE main sql.BasicExtractor:78 - extracted value ([project_2_2_0_] : [BIGINT]) - [2]
Hibernate: update employee set age=?, first_name=?, last_name=? where employee_id=? and version=?
10:36:46,426 TRACE main sql.BasicBinder:81 - binding parameter [1] as [INTEGER] - [0]
10:36:46,426 TRACE main sql.BasicBinder:81 - binding parameter [2] as [VARCHAR] - [Bogumil]
10:36:46,427 TRACE main sql.BasicBinder:81 - binding parameter [3] as [VARCHAR] - [Bednarek]
10:36:46,427 TRACE main sql.BasicBinder:81 - binding parameter [4] as [BIGINT] - [1]
10:36:46,427 TRACE main sql.BasicBinder:81 - binding parameter [5] as [INTEGER] - [58]
此外，我发现如果我在同一个事务中选择并更新记录，hibernate不会增加版本，一切正常。
又一次观察。删除＆＃39;设置＆＃39;映射文件中的元素，一切正常：
<set name="projects" table="employee_to_project" inverse="true">
<key column="employee_id"/>
<many-to-many column="project_id" class="ProjectEntity"/>
</set>
有人可以解释一下，为什么hibernate增加了版本，因此我得到了例外？
有关我的申请的更多详情：
答案 0 :(得分：0)
从堆栈跟踪中，问题是＆＃34; 行被另一个事务更新或删除（或未保存的值映射不正确）＆＃34;。
如果问题与交易有关，则有三种可能：