多个数据源导致HibernateException？

Question

对于我的grails项目，我的大多数类都有一个内存中的h2数据库，但只是为所有与用户相关的类添加了一个持久数据库。在启动时，应用程序会执行几个线程。在添加第二个数据源之后，我得到了HibernateExceptions。具体来说，

Illegal attempt to associate a collection with two open sessions; nested exception is org.hibernate.HibernateException

它们只在第一个或两个线程中发生，然后其余的线程执行时不会出现问题。这让我相信这是数据库第一次启动时的某种并发问题。发生错误的代码是：

instance.customer = customerService.retrieveCustomer instance
instance.name = instance.customer?.name

Instance.withTransaction{
    instance.customer.save()  // <-- THIS LINE IS THE PROBLEM
    instance.save()
}

我不知道这是数据库问题、hibernate问题还是其他问题。运行Grails 2.0.4

完整的堆栈跟踪：

| Error 2013-03-20 16:25:30,995 [pool-16-thread-1] ERROR kindlingcustomers.InstanceList  - k_54 Illegal attempt to associate a collection with two open sessions; nested exception is org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions org.springframework.orm.hibernate3.HibernateSystemException: Illegal attempt to associate a collection with two open sessions; nested exception is org.hibernate.HibernateException: Illegal attempt to associate a collection with two open sessions
    at org.springframework.orm.hibernate3.SessionFactoryUtils.convertHibernateAccessException(SessionFactoryUtils.java:683)
    at org.springframework.orm.hibernate3.HibernateAccessor.convertHibernateAccessException(HibernateAccessor.java:412)
    at org.springframework.orm.hibernate3.HibernateTemplate.doExecute(HibernateTemplate.java:411)
    at org.springframework.orm.hibernate3.HibernateTemplate.execute(HibernateTemplate.java:339)
    at org.codehaus.groovy.grails.orm.hibernate.metaclass.SavePersistentMethod.performSave(SavePersistentMethod.java:56)
    at org.codehaus.groovy.grails.orm.hibernate.metaclass.AbstractSavePersistentMethod.doInvokeInternal(AbstractSavePersistentMethod.java:212)
    at org.codehaus.groovy.grails.orm.hibernate.metaclass.AbstractDynamicPersistentMethod.invoke(AbstractDynamicPersistentMethod.java:63)
    at org.codehaus.groovy.grails.commons.metaclass.DynamicMethodInvocation$invoke.call(Unknown Source)
    at org.codehaus.groovy.grails.orm.hibernate.HibernateGormInstanceApi.save(HibernateGormEnhancer.groovy:847)
    at kindlingcustomers.Customer.save(Customer.groovy)
    at kindlingcustomers.Customer$save$0.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:42)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:112)
    at kindlingcustomers.InstanceList$__clinit__closure5_closure8.doCall(InstanceList.groovy:67)
    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 com.springsource.loaded.ri.ReflectiveInterceptor.jlrMethodInvoke(ReflectiveInterceptor.java:1231)
    at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
    at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
    at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1047)
    at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1110)
    at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:877)
    at groovy.lang.Closure.call(Closure.java:412)
    at kindlingcustomers.InstanceList$__clinit__closure5_closure8.call(InstanceList.groovy)
    at org.codehaus.groovy.runtime.ConvertedClosure.invokeCustom(ConvertedClosure.java:51)
    at org.codehaus.groovy.runtime.ConversionHandler.invoke(ConversionHandler.java:82)
    at com.sun.proxy.$Proxy30.doInTransaction(Unknown Source)
    at org.springframework.transaction.support.TransactionTemplate.execute(TransactionTemplate.java:130)
    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 com.springsource.loaded.ri.ReflectiveInterceptor.jlrMethodInvoke(ReflectiveInterceptor.java:1231)
    at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite$PojoCachedMethodSite.invoke(PojoMetaMethodSite.java:189)
    at org.codehaus.groovy.runtime.callsite.PojoMetaMethodSite.call(PojoMetaMethodSite.java:53)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:42)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
    at org.grails.datastore.gorm.GormStaticApi.withTransaction(GormStaticApi.groovy:573)
    at kindlingcustomers.Instance.withTransaction(Instance.groovy)
    at kindlingcustomers.Instance$withTransaction.call(Unknown Source)
    at org.codehaus.groovy.runtime.callsite.CallSiteArray.defaultCall(CallSiteArray.java:42)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:108)
    at org.codehaus.groovy.runtime.callsite.AbstractCallSite.call(AbstractCallSite.java:116)
    at kindlingcustomers.InstanceList$__clinit__closure5.doCall(InstanceList.groovy:66)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
    at java.lang.reflect.Method.invoke(Method.java:597)
    at com.springsource.loaded.ri.ReflectiveInterceptor.jlrMethodInvoke(ReflectiveInterceptor.java:1231)
    at org.codehaus.groovy.reflection.CachedMethod.invoke(CachedMethod.java:90)
    at groovy.lang.MetaMethod.doMethodInvoke(MetaMethod.java:233)
    at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:1047)
    at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1110)
    at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:877)
    at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:921)
    at groovy.lang.ExpandoMetaClass.invokeMethod(ExpandoMetaClass.java:1110)
    at groovy.lang.MetaClassImpl.invokeMethod(MetaClassImpl.java:877)
    at groovy.lang.Closure.call(Closure.java:412)
    at groovy.lang.Closure.call(Closure.java:406)
    at groovy.lang.Closure.run(Closure.java:490)
    at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
    at java.lang.Thread.run(Thread.java:680)

我的数据源：

environments {
    development {
        dataSource {
            dbCreate = "create-drop" // one of 'create', 'create-drop', 'update', 'validate', ''
            url = "jdbc:h2:mem:devDb;MVCC=TRUE"
        }

        dataSource_users {
            dbCreate = "update" 
            url = "jdbc:h2:devDb;MVCC=TRUE;LOCK_TIMEOUT=10000"
        }
    }
    test {
        dataSource {
            dbCreate = "update"
            url = "jdbc:h2:mem:testDb;MVCC=TRUE"
        }

        dataSource_users {
            dbCreate = "update"
            url = "jdbc:h2:testDb;MVCC=TRUE;LOCK_TIMEOUT=10000"
        }
    }
    production {
        dataSource {
            dbCreate = "create-drop"
            url = "jdbc:h2:mem;MVCC=TRUE"
            pooled = true
            properties {
               maxActive = -1
               minEvictableIdleTimeMillis=1800000
               timeBetweenEvictionRunsMillis=1800000
               numTestsPerEvictionRun=3
               testOnBorrow=true
               testWhileIdle=true
               testOnReturn=true
               validationQuery="SELECT 1"
            }
        }

        dataSource_users {
            dbCreate = "update"
            url = "jdbc:h2:prodDb;MVCC=TRUE;LOCK_TIMEOUT=10000"
        }
    }
}

Answer 1

我设法用一个相当草率的变通方法抑制了异常。希望它能帮助其他人，但如果有人有其他解决方案或对这个问题有任何见解，我很乐意听到。

无论如何，您希望在适当的时候调用merge()而不是save()。我不知道如何确定一个实例是否跨多个会话被引用，所以我只是将每个存储都包装在try-catch块中，然后在出现异常时调用merge()。这不是最漂亮的解决方案，但它是有效的。

def customerService = AH.application.mainContext.customerService
instance.customer = customerService.retrieveCustomer instance
instance.name = instance.customer?.name ?: instance.domain?.tokenize('.')[0].capitalize() ?: ''

Instance.withTransaction{
    try{ instance.customer.save() } 
    catch (Exception e) { instance.customer.merge() }

    try { instance.save() } 
    catch (Exception e) { instance.merge() }                    
}

Answer 2

在Hibernate中，每个PersistedCollection ( Hibernate为任何集合关系设置的包装类)都只与一个Session实例相关联。这是Hibernate确保维护实例标识的Session级别保证的工作的一部分。

您得到的错误指示您在一个Session中加载了一个具有集合的实体，然后尝试在另一个Session中对其执行.save()操作。这可能不起作用，除非您首先采取步骤将该实体与另一个Session相关联，这可以通过调用otherSession.merge(entity)来完成。这就是你的变通方法“有效”的原因。

您应该看看Hibernate文档的this section，它处理从一个数据源到另一个数据源的复制。不过，我不确定replicate在Ruby/Grails中是否可用。