行被另一个事务更新或删除(或未保存的值映射不正确) [英] Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect)

问题描述

我有一个在网络服务器上运行的 Java 项目.我总是遇到这个异常.

I have a java project that runs on a webserver. I always hit this exception.

我阅读了一些文档，发现悲观锁定(或乐观，但我读到悲观更好)是防止此异常的最佳方法.

I read some documentation and found that pessimistic locking (or optimistic, but I read that pessimistic is better) is the best way to prevent this exception.

但我找不到任何清楚的例子来解释如何使用它.

But I couldn't find any clear example that explains how to use it.

我的方法是:

    @Transactional
    public void test(Email email, String subject) {
        getEmailById(String id);
        email.setSubject(subject);
        updateEmail(email);
    }

同时:

• Email 是一个 Hibernate 类(它将是数据库中的一个表)
• getEmailById(String id) 是一个返回 email 的函数(这个方法没有用 @Transactional 注释)
• updateEmail(email):是一种更新电子邮件的方法.

• Email is a Hibernate class (it will be a table in the database)
• getEmailById(String id) is a function that returns an email (this method is not annotated with @Transactional)
• updateEmail(email): is a method that updates the email.

注意:我使用 Hibernate 进行保存、更新和更新依此类推(例如:session.getcurrentSession.save(email))

Note: I use Hibernate for save, update & so on (example: session.getcurrentSession.save(email))

例外:

ERROR 2011-12-21 15:29:24,910 Could not synchronize database state with session [myScheduler-1]
org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [email#21]
    at org.hibernate.persister.entity.AbstractEntityPersister.check(AbstractEntityPersister.java:1792)
    at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:2435)
    at org.hibernate.persister.entity.AbstractEntityPersister.updateOrInsert(AbstractEntityPersister.java:2335)
    at org.hibernate.persister.entity.AbstractEntityPersister.update(AbstractEntityPersister.java:2635)
    at org.hibernate.action.EntityUpdateAction.execute(EntityUpdateAction.java:115)
    at org.hibernate.engine.ActionQueue.execute(ActionQueue.java:279)
    at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:263)
    at org.hibernate.engine.ActionQueue.executeActions(ActionQueue.java:168)
    at org.hibernate.event.def.AbstractFlushingEventListener.performExecutions(AbstractFlushingEventListener.java:321)
    at org.hibernate.event.def.DefaultFlushEventListener.onFlush(DefaultFlushEventListener.java:50)
    at org.hibernate.impl.SessionImpl.flush(SessionImpl.java:1027)
    at org.hibernate.impl.SessionImpl.managedFlush(SessionImpl.java:365)
    at org.hibernate.transaction.JDBCTransaction.commit(JDBCTransaction.java:137)
    at org.springframework.orm.hibernate3.HibernateTransactionManager.doCommit(HibernateTransactionManager.java:656)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.processCommit(AbstractPlatformTransactionManager.java:754)
    at org.springframework.transaction.support.AbstractPlatformTransactionManager.commit(AbstractPlatformTransactionManager.java:723)
    at org.springframework.transaction.interceptor.TransactionAspectSupport.commitTransactionAfterReturning(TransactionAspectSupport.java:393)
    at org.springframework.transaction.interceptor.TransactionInterceptor.invoke(TransactionInterceptor.java:120)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    at org.springframework.aop.framework.JdkDynamicAopProxy.invoke(JdkDynamicAopProxy.java:202)
    at $Proxy130.generateEmail(Unknown Source)
    at com.admtel.appserver.tasks.EmailSender.run(EmailNotificationSender.java:33)
    at com.admtel.appserver.tasks.EmailSender$$FastClassByCGLIB$$ea0d4fc2.invoke(<generated>)
    at net.sf.cglib.proxy.MethodProxy.invoke(MethodProxy.java:149)
    at org.springframework.aop.framework.Cglib2AopProxy$CglibMethodInvocation.invokeJoinpoint(Cglib2AopProxy.java:688)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:150)
    at org.springframework.aop.aspectj.AspectJAfterThrowingAdvice.invoke(AspectJAfterThrowingAdvice.java:55)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:161)
    at org.springframework.aop.framework.adapter.AfterReturningAdviceInterceptor.invoke(AfterReturningAdviceInterceptor.java:50)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:161)
    at org.springframework.aop.framework.adapter.MethodBeforeAdviceInterceptor.invoke(MethodBeforeAdviceInterceptor.java:50)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:161)
    at org.springframework.aop.interceptor.ExposeInvocationInterceptor.invoke(ExposeInvocationInterceptor.java:89)
    at org.springframework.aop.framework.ReflectiveMethodInvocation.proceed(ReflectiveMethodInvocation.java:172)
    at org.springframework.aop.framework.Cglib2AopProxy$DynamicAdvisedInterceptor.intercept(Cglib2AopProxy.java:621)
    at com.admtel.appserver.tasks.EmailNotificationSender$$EnhancerByCGLIB$$33eb7303.run(<generated>)
    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.util.MethodInvoker.invoke(MethodInvoker.java:273)
    at org.springframework.scheduling.support.MethodInvokingRunnable.run(MethodInvokingRunnable.java:65)
    at org.springframework.scheduling.support.DelegatingErrorHandlingRunnable.run(DelegatingErrorHandlingRunnable.java:51)
    at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:441)
    at java.util.concurrent.FutureTask$Sync.innerRunAndReset(FutureTask.java:317)
    at java.util.concurrent.FutureTask.runAndReset(FutureTask.java:150)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.access$101(ScheduledThreadPoolExecutor.java:98)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.runPeriodic(ScheduledThreadPoolExecutor.java:180)
    at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:204)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:886)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:908)
    at java.lang.Thread.run(Thread.java:680)
ERROR 2011-12-21 15:29:24,915 [ exception thrown < EmailNotificationSender.run() > exception message Object of class [Email] with identifier [211]: optimistic locking failed; nested exception is org.hibernate.StaleObjectStateException: Row was updated or deleted by another transaction (or unsaved-value mapping was incorrect): [Email#21] with params ] [myScheduler-1]
org.springframework.orm.hibernate3.HibernateOptimisticLockingFailureException: Object of class [Email] with identifier [21]: optimistic locking failed; nested exception is 

推荐答案

一般不推荐使用悲观锁，它在数据库端的性能方面成本非常高.你提到的问题(代码部分)有几点不清楚比如:

Pessimistic locking is generally not recommended and it's very costly in terms of performance on database side. The problem that you have mentioned (the code part) a few things are not clear such as:

• 如果您的代码同时被多个线程访问.
• 您如何创建 session 对象(不确定您是否使用 Spring)?

• If your code is being accessed by multiple threads at the same time.
• How are you creating session object (not sure if you are using Spring)?

Hibernate 会话对象不是线程安全的.因此，如果有多个线程访问同一个会话并尝试更新同一个数据库实体，您的代码可能最终会出现这样的错误情况.

Hibernate Session objects are NOT thread-safe. So if there are multiple threads accessing the same session and trying to update the same database entity, your code can potentially end up in an error situation like this.

所以这里发生的事情是多个线程尝试更新同一个实体，一个线程成功，当下一个线程提交数据时，它看到它已经被修改并最终抛出 StaleObjectStateException.

So what happens here is that more than one thread tries to update the same entity, one thread succeeds and when the next thread goes to commit the data, it sees that its already been modified and ends up throwing StaleObjectStateException.

编辑:

有一种方法可以在 Hibernate 中使用悲观锁定.查看此链接.但是这种机制似乎存在一些问题.但是，我在 hibernate (HHH-5275) 中发现了一个错误.bug中提到的场景如下:

There is a way to use Pessimistic Locking in Hibernate. Check out this link. But there seems to be some issue with this mechanism. I came across posting a bug in hibernate (HHH-5275), however. The scenario mentioned in the bug is as follows:

两个线程正在读取同一个数据库记录；其中一个线程应该使用悲观锁定从而阻塞另一个线程.但两个线程都可以读取数据库记录导致测试失败.

Two threads are reading the same database record; one of those threads should use pessimistic locking thereby blocking the other thread. But both threads can read the database record causing the test to fail.

这与您面临的情况非常接近.如果这不起作用，请尝试此操作，我能想到的唯一方法是使用 本机 SQL 查询，您可以在其中实现 使用 SELECT FOR UPDATE 查询在 postgres 数据库中使用悲观锁定.

This is very close to what you are facing. Please try this if this does not work, the only way I can think of is using Native SQL queries where you can achieve pessimistic locking in postgres database with SELECT FOR UPDATE query.

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