在JPA / Hibernate的PostLoad中读取一个集合 [英] Reading a Set in PostLoad on JPA/Hibernate

问题描述

我有一个OneToMany关系的简单实体：

  @Column（name =TITLE）
 private字符串_title; 
 @OneToMany（cascade = CascadeType.ALL，fetch = FetchType.EAGER）
 @JoinColumn（name =PROJECT_ID）
 private Set< Device> _设备; 
 @OneToMany（cascade = CascadeType.ALL，fetch = FetchType.EAGER）
 @JoinColumn（name =PROJECT_ID）
 private Set< Firm> _firms; 
  

我想在PostLoad方法中使用我的设置进行操作。

  @PostLoad 
 private void copyToProperty（）{
 title.set（_title）; 
 if（_devices！= null&&！_devices.isEmpty（））
 // DO Stuff HERE 
} 
  

但是，当我尝试访问_devices时，出现以下异常：

 线程main中的异常javax.persistence.PersistenceException：org.hibernate.LazyInitializationException：无法懒惰地初始化集合，没有会话或会话已关闭
在org.hibernate.ejb.AbstractEntityManagerImpl.convert（AbstractEntityManagerImpl。 
 at org.hibernate.ejb.AbstractEntityManagerImpl.find（AbstractEntityManagerImpl.java:635）
 at org.hibernate.ejb.AbstractEntityManagerImpl.find（AbstractEntityManagerImpl.java:589）
 （com.dooapp.jpa.Main.main（Main.java:57））
 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.intellij.rt.execution.application.AppMain.main（AppMain.java:120）
  

有没有人知道为什么当我在FetchType.EAGER上时我得到一个LazyInitializationException？

不幸的是，Hibernate根本不允许你这样做。在 @PostLoad 方法中，您不允许触摸实体中的任何关联。这是一个长期存在的主要错误。

有关原始错误，请参阅： https： //issues.jboss.org/browse/JBAS-5474 。错误关闭后（仍未解决），立即重新打开一个新的： https： //hibernate.onjira.com/browse/HHH-6043

如果这个bug出错了（我猜是这样），请投票支持。 / p>

I have a simple entity with OneToMany relation :

@Column(name = "TITLE")
private String _title;
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinColumn(name = "PROJECT_ID")
private Set<Device> _devices;
@OneToMany(cascade = CascadeType.ALL, fetch = FetchType.EAGER)
@JoinColumn(name = "PROJECT_ID")
private Set<Firm> _firms;

And I want to do stuff with my set in the PostLoad method

@PostLoad
private void copyToProperty() {
    title.set(_title);
    if (_devices != null && !_devices.isEmpty())
       //DO Stuff HERE
}

But, when I try to access to _devices I get this exception :

Exception in thread "main" javax.persistence.PersistenceException: org.hibernate.LazyInitializationException: failed to lazily initialize a collection, no session or session was closed
at org.hibernate.ejb.AbstractEntityManagerImpl.convert(AbstractEntityManagerImpl.java:1215)
at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:635)
at org.hibernate.ejb.AbstractEntityManagerImpl.find(AbstractEntityManagerImpl.java:589)
at com.dooapp.jpa.Main.main(Main.java:57)
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.intellij.rt.execution.application.AppMain.main(AppMain.java:120)

Does anyone know why I'm getting a LazyInitializationException as long as I'm on FetchType.EAGER?

And how can do this stuff working?

Thank's

解决方案

Hibernate unfortunately simply doesn't allow you to do that. In an @PostLoad method, you are not allowed to touch any association in the entity. This is a long standing major bug.

For the original bug see: https://issues.jboss.org/browse/JBAS-5474. After the bug was closed (while still unresolved), a new one was immediately re-opened here: https://hibernate.onjira.com/browse/HHH-6043

If this bug bugs you (I guess it does), please vote for it.

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