如何在使用JPA和Hibernate时解决LazyInitializationException [英] How to solve the LazyInitializationException when using JPA and Hibernate

问题描述

我正在为一个想要使用延迟初始化的客户开发一个项目。
当使用默认的延迟加载模式映射类时，它们总是会得到延迟初始化异常。

  @JoinTable（name =join_profilo_funzional，joinColumns = {@JoinColumn（name =profilo_id，referencedColumnName =profilo_id）}，inverseJoinColumns = {@JoinColumn（name =funzionalita_id，referencedColumnName =funzionalita_id）}）
 / /@ManyToMany(fetch=FetchType.EAGER） - 如果未注释，则不会出现异常
 @ManyToMany 
私人收藏< Funzionalita> funzionalitaIdCollection; 
  

有没有使用JPA类的标准模式来避免这种错误？

欢迎使用片段，非常感谢您的时间。

解决方案

Hibernate 4.1.6终于解决了这个问题：https://hibernate.atlassian.net/browse/HHH-7457

您需要设置hibernate-property hibernate。 enable_lazy_load_no_trans = true

以下是在Spring中执行的操作：

  < bean id =entityManagerFactory
 class =org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean> 
< property name =dataSourceref =myDataSource/> 
< property name =packagesToScanvalue =com.mycompany.somepackage/> 
< property name =jpaVendorAdapterref =hibernateVendorAdapter/> 
< property name =jpaDialectref =jpaDialect/> 
< property name =jpaProperties> 
<道具> 
< prop key =hibernate.enable_lazy_load_no_trans> true< / prop> 
< /道具> 
< / property> 
< / bean> 
  

瞧;现在，您不必担心LazyInitializationException，而在hibernate会话之外导航您的领域模型（JPA发言中的持久性上下文）。

I am working on a project for a customer who wants to use lazy initialization. They always get "lazy initialization exception" when mapping classes with the default lazy loading mode.

@JoinTable(name = "join_profilo_funzionalita", joinColumns = {@JoinColumn(name =    "profilo_id", referencedColumnName = "profilo_id")}, inverseJoinColumns = {@JoinColumn(name = "funzionalita_id", referencedColumnName = "funzionalita_id")})
//@ManyToMany(fetch=FetchType.EAGER) - no exceptions if uncommented
@ManyToMany 
private Collection<Funzionalita> funzionalitaIdCollection;

Is there a standard pattern using JPA classes to avoid this error?

Snippets are welcome, thanks a lot for your time.

解决方案

Hibernate 4.1.6 finally solves this issue: https://hibernate.atlassian.net/browse/HHH-7457

You need to set the hibernate-property hibernate.enable_lazy_load_no_trans=true

Here's how to do it in Spring:

<bean id="entityManagerFactory"
      class="org.springframework.orm.jpa.LocalContainerEntityManagerFactoryBean">
    <property name="dataSource" ref="myDataSource"/>
    <property name="packagesToScan" value="com.mycompany.somepackage"/>
    <property name="jpaVendorAdapter" ref="hibernateVendorAdapter"/>
    <property name="jpaDialect" ref="jpaDialect"/>
    <property name="jpaProperties">
        <props>
            <prop key="hibernate.enable_lazy_load_no_trans">true</prop>
        </props>
    </property>
</bean>

Voila; Now you don't have to worry about LazyInitializationException while navigating your domain-model outside of a hibernate-session (persistence-context in "JPA-speak")

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