尝试在EntityManager关闭后加载懒惰关系

Question

我有三个spring + JPA项目...一个基础项目A，一个插件项目B和实际项目C.在C中，其他两个项目都以导入为A.jar和B.jar。每个项目都有自己的ApplicationContext.xml。叶子项目（即C）在proeject-A的appcontext.xml中提到了自定义位置的persistence.xml（启动项目A在整个类路径中查找appcontext.xml和persistence.xml，因此可以从B加载xml和C）。

下面

是我的配置， applicationContext.xml中 - 在项目中的

<bean id="jpaQueryManager" class="com.motherframework.base.dao.jpa.JPAQueryManager"> 
    <property name="jpaTemplate" ref="jpaTemplate"/> 
</bean> 

<bean id="jpaTemplate" class="org.springframework.orm.jpa.JpaTemplate"> 
    <property name="entityManagerFactory" ref="entityManagerFactory"/> 
</bean> 

<bean id="entityManagerFactory" class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean"> 
    <!-- <property name="persistenceUnitManager" ref="pum"/> 
    <property name="persistenceUnitName" value="SchoolWebsitePersistenceUnit"/> --> 
    <property name="persistenceXmlLocation" value="classpath*:configuration/xml/persistence.xml"/> 
    <!-- <property name="persistenceUnitPostProcessors"> 
     <list> 
     <bean class="com.motherframework.base.dao.jpa.EntityScanner"/> 
     </list> 
    </property> --> 
    <property name="dataSource"><ref bean="dataSource"/></property> 
    <property name="jpaVendorAdapter"> 
     <bean class="org.springframework.orm.jpa.vendor.HibernateJpaVendorAdapter"> 
     <property name="showSql" value="true"/> 
     <property name="generateDdl" value="true"/> 
     <property name="databasePlatform" value="org.hibernate.dialect.MySQLDialect"/> 
     </bean> 
    </property> 
</bean> 

，这是我的persistence.xml

<persistence-unit name="SchoolWebsitePersistenceUnit" transaction-type="RESOURCE_LOCAL"> 

    <provider>org.hibernate.ejb.HibernatePersistence</provider> 
    <class>com.motherframework.plugin.school.entity.Account</class> 
    <class>com.motherframework.plugin.school.entity.Module</class> 
    <class>com.motherframework.plugin.school.entity.NavigationMenu</class> 
    <class>com.motherframework.plugin.school.entity.User</class> 


    <properties> 
     <property name="dialect" value="org.hibernate.dialect.SQLServerDialect"/> 
     <property name="hibernate.connection.autocommit" value="true"/> 
     <property name="hibernate.cache.provider_class" value="org.hibernate.cache.NoCacheProvider"/> 
     <property name="hibernate.show_sql" value="true"/> 
     <property name="hibernate.archive.autodetection" value="class, hbm"/> 
    </properties> 

</persistence-unit> 

现在从我的客户端类（主要方法）我是使用@transactional Service-DAO层获取实体（例如用户）。

User u = ((TestService) ApplicationContext.getBean("testService")).fetchUser(); 
// FROM User u WHERE u.id=1 (Note: no INNER JOIN u.account) 

print(u.getAccount()) 

应该给我NULL，但它引发异常，

DEBUG DefaultListableBeanFactory:241 - Returning cached instance of singleton bean 'org.springframework.transaction.interceptor.TransactionInterceptor#0' 
DEBUG AnnotationTransactionAttributeSource:106 - Adding transactional method 'fetchUser' with attribute: PROPAGATION_REQUIRED,ISOLATION_DEFAULT,readOnly; '' 
DEBUG DefaultListableBeanFactory:241 - Returning cached instance of singleton bean 'jpaTxManager' 
DEBUG JpaTransactionManager:365 - Creating new transaction with name [com.motherframework.plugin.test.service.TestService.fetchUser]: PROPAGATION_REQUIRED,ISOLATION_DEFAULT,readOnly; '' 
DEBUG JpaTransactionManager:323 - Opened new EntityManager [org.hibernate.ejb.EntityManagerImpl@d964af] for JPA transaction 
DEBUG JpaTransactionManager:355 - Exposing JPA transaction as JDBC transaction [SimpleConnectionHandle: jdbc:mysql://localhost:3306/schooldb, UserName=scott@localhost, MySQL-AB JDBC Driver] 
DEBUG TransactionSynchronizationManager:183 - Bound value [org.springframework.jdbc.datasource.ConnectionHolder@45378f] for key [org.apache.commons.dbcp.BasicDataSource@181b3d4] to thread [main] 
DEBUG TransactionSynchronizationManager:183 - Bound value [org.springframework.orm.jpa.EntityManagerHolder@29d65b] for key [org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean@b8176d] to thread [main] 
DEBUG TransactionSynchronizationManager:258 - Initializing transaction synchronization 
DEBUG TransactionInterceptor:381 - Getting transaction for [com.motherframework.plugin.test.service.TestService.fetchUser] 
DEBUG TransactionSynchronizationManager:139 - Retrieved value [org.springframework.orm.jpa.EntityManagerHolder@29d65b] for key [org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean@b8176d] bound to thread [main] 
DEBUG TransactionSynchronizationManager:139 - Retrieved value [org.springframework.orm.jpa.EntityManagerHolder@29d65b] for key [org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean@b8176d] bound to thread [main] 
DEBUG TransactionSynchronizationManager:139 - Retrieved value [org.springframework.orm.jpa.EntityManagerHolder@29d65b] for key [org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean@b8176d] bound to thread [main] 
Hibernate: select user0_.id as id3_, user0_.accountId as accountId3_, user0_.email as email3_, user0_.loginId as loginId3_, user0_.name as name3_, user0_.password as password3_ from User user0_ where user0_.id=1 
DEBUG TransactionInterceptor:410 - Completing transaction for [com.motherframework.plugin.test.service.TestService.fetchUser] 
DEBUG JpaTransactionManager:925 - Triggering beforeCommit synchronization 
DEBUG JpaTransactionManager:938 - Triggering beforeCompletion synchronization 
DEBUG JpaTransactionManager:752 - Initiating transaction commit 
DEBUG JpaTransactionManager:462 - Committing JPA transaction on EntityManager [org.hibernate.ejb.EntityManagerImpl@d964af] 
DEBUG JpaTransactionManager:951 - Triggering afterCommit synchronization 
DEBUG JpaTransactionManager:967 - Triggering afterCompletion synchronization 
DEBUG TransactionSynchronizationManager:311 - Clearing transaction synchronization 
DEBUG TransactionSynchronizationManager:229 - Removed value [org.springframework.orm.jpa.EntityManagerHolder@29d65b] for key [org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean@b8176d] from thread [main] 
DEBUG TransactionSynchronizationManager:229 - Removed value [org.springframework.jdbc.datasource.ConnectionHolder@45378f] for key [org.apache.commons.dbcp.BasicDataSource@181b3d4] from thread [main] 
DEBUG JpaTransactionManager:548 - Closing JPA EntityManager [org.hibernate.ejb.EntityManagerImpl@d964af] after transaction 
DEBUG EntityManagerFactoryUtils:329 - Closing JPA EntityManager 
856 [main] ERROR org.hibernate.LazyInitializationException - could not initialize proxy - no Session 
org.hibernate.LazyInitializationException: could not initialize proxy - no Session 
at   org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:132) 
at  org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:174) 
Exception in thread "main" org.hibernate.LazyInitializationException: could not initialize proxy - no Session 
at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:132) 
at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:174) 
at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:190) 
at  com.motherframework.plugin.school.entity.Account_$$_javassist_3.toString(Account_$$_javassist_3.java) 
at java.lang.String.valueOf(Unknown Source) 
at java.io.PrintStream.println(Unknown Source) 
at 

你可以找到我的实体管理器是关闭的，所以它会给出一个异常，如果它试图在用户获取帐户....我明白...但如果entitymanager关闭，那么为什么它试图做到这一点？如何阻止它？配置有问题吗？

还有一件事，我正在使用的entitymanagerfactory适用于生产环境（和tomcat 7）中的公共web应用程序？

在此先感谢.. :)

感谢Nizet..you意味着我PersistenceContext已经为EntityManager的关闭关闭。但是，如果entity实际上超出了PersistenceContext，那么为什么它应该尝试获取它的关系呢？它是一个简单的POJO，而不是@Entity了。对于第二个问题，是的我错过了

<tx:annotation-driven transaction-manager="jpaTxManager"/> 
<bean id="jpaTxManager" class="org.springframework.orm.jpa.JpaTransactionManager"> 
    <property name="entityManagerFactory"><ref bean="entityManagerFactory"/></property> 
    <property name="dataSource"><ref bean="dataSource"/></property> 
</bean> 

请检查我的Entitymanager类型和transactionmanager ...是否适合生产？

这是我的DS：

<bean id="dataSource" destroy-method="close" class="org.apache.commons.dbcp.BasicDataSource"> 
<property name="driverClassName" value="${motherframework.configuration.db.driver}" /> 
<property name="url" value="${motherframework.configuration.db.url}" /> 
<property name="username" value="${motherframework.configuration.db.username}" /> 
<property name="password" value="${motherframework.configuration.db.password}" /> 

但做ü要表示，虽然持久化上下文被关闭，“用户”对象仍持有部分物业，这使得它与正常POJO不同类？

Answer 1

您的用户与帐户有关联。该帐户是延迟加载的。这意味着，如果您第一次调用帐户上的任何方法（例如user.getAccount().getName()），Hibernate将从数据库加载帐户的状态，并返回帐户的名称。只有在实体管理器处于打开状态时才能这样做，否则，它不再与数据库建立任何连接。

它不能返回null：返回null将意味着：这个用户没有一个帐户，这是错误的。

如果您想在实体管理器关闭后访问帐户，那么您需要在关闭实体管理器之前初始化该帐户。这是没有办法的。

关于你的配置，不，它不是为生产做好准备：

• showSql应该是假的
• hibernate.show_sql应该是假的
• generateDdl应该是假的
• hibernate.connection.autocommit应该是假的
• 你还没有显示你的数据源定义，这是一个非常重要的部分