JSF + Hibernate:集合未与任何会话关联 [英] JSF + Hibernate: Collection is not associated with any session
问题描述
首先，我使用Java EE，将Hibernate与EntityManager和PrimeFaces结合使用.
First of all, I use Java EE, Hibernate with EntityManager and PrimeFaces.
我有一个EJB模块(业务逻辑和域)和两个WAR模块(Jersey WS和JSF PrimeFaces).
I have one EJB module (business logic and domain) and two WAR modules (Jersey WS and JSF PrimeFaces).
我决定在JSF WAR模块中初始化延迟集合，以避免延迟初始化异常.我不使用扩展实体管理器.
I decided to initialize lazy collections in JSF WAR module to avoid lazy initialization exception. I don't use extended entity manager.
@ManagedBean(name = "company")
@SessionScoped
public class CompanyBean {
@EJB
private CompanyFacade cf;
...
public String showDetails(Long id) {
company = cf.find(id);
Hibernate.initialize(company.getCompanyTypes());
Hibernate.initialize(company.getPrimaryUser());
Hibernate.initialize(company.getBlocked());
Hibernate.initialize(company.getAddresses());
Hibernate.initialize(company.getContacts());
return "DETAILS";
}
...
}
然后我得到:
Caused by: org.hibernate.HibernateException: collection is not associated with any session
at org.hibernate.collection.AbstractPersistentCollection.forceInitialization(AbstractPersistentCollection.java:474)
at org.hibernate.Hibernate.initialize(Hibernate.java:417)
at minepackage.CompanyBean.showDetails(CompanyBean.java:79)
...
Caused by: org.hibernate.HibernateException: collection is not associated with any session
at org.hibernate.collection.AbstractPersistentCollection.forceInitialization(AbstractPersistentCollection.java:474)
at org.hibernate.Hibernate.initialize(Hibernate.java:417)
at minepackage.CompanyBean.showDetails(CompanyBean.java:79)
...
我不明白.从数据库中获取初始化之前的一行时，必须有一个会话，不是吗?我以类似的方式在WS模块中初始化属性，并且可以正常工作.
I don't understand it. There has to be a session when one line before the initialization it was fetched from database, doesn't it? I initialize attributes in WS module in similar way and there it's working.
知道发生了什么事吗?
推荐答案
我认为在EJB完成后会话关闭，因此对象处于 detached 状态.因此Hibernate.initialize()将不再起作用.您在这里有多种选择:
I think the session is closed after your EJB finished, so the objects are in detached state. So Hibernate.initialize() won't work any more. You have multiple options here:
- 在客户端(在您的JSF bean或servlet过滤器中)打开事务.这样，当您呼叫
Hibernate.initialize()时，会话仍将打开. - 修改您的EJB以加载完整的对象和所有必需的集合.您可以在其中使用访存联接和/或使用
Hibernate.initialize(). - 在EJB中创建更细粒度的API.
CompanyFacade.getAddressesByCompany()之类的方法.
- Open the transaction on the client side (in your JSF bean or in a servlet filter). This way the session will still be open when your are calling
Hibernate.initialize(). - Modify your EJB to load the full object and all the required collections. You could use fetch joins and/or use
Hibernate.initialize()there. - Create a more fine grained API in your EJB. Method like
CompanyFacade.getAddressesByCompany().
我希望将后两者结合起来.使用访存联接在find方法中加载一对一和多对一关系，并添加其他方法来加载一对多集合(如地址).因为它减少了数据库查询的次数，所以这也将提高后端的性能.
I would prefer a combination of the latter two. Use fetch joins to load the one-to-one and many-to-one relationships in your find method and add extra methods for loading the one-to-many collections (like addresses). This will also improve performance of your backend because it reduces the number of database queries.
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