Java Hibernate: LazyInitializationException: 未能延迟初始化角色集合。无法初始化代理 - 没有会话
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原文地址: http://stackoverflow.com/questions/42925823/
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Hibernate: LazyInitializationException: failed to lazily initialize a collection of role. Could not initialize proxy - no Session
提问by Orest
I have next error: nested exception is org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.Model.entities, could not initialize proxy - no Session
我有下一个错误： nested exception is org.hibernate.LazyInitializationException: failed to lazily initialize a collection of role: com.example.Model.entities, could not initialize proxy - no Session
My Modelentity:
我的Model实体：
class Model {
...
@OneToMany(fetch = FetchType.LAZY, mappedBy = "model", orphanRemoval = true)
@Cascade(CascadeType.ALL)
@Fetch(value = FetchMode.SUBSELECT)
public Set<Entity> getEntities() {
return entities;
}
public void addEntity(Entity entity) {
entity.setModel(this);
entities.add(entity);
}
}
And I have a service class:
我有一个服务类：
@Service
@Transactional
class ServiceImpl implements Service {
@Override
public void process(Model model) {
...
model.addEntity(createEntity());
...
}
}
I'm calling service from another service method:
我正在从另一个服务方法调用服务：
@Override
@JmsListener(destination = "listener")
public void handle(final Message message) throws Exception {
Model model = modelService.getById(message.getModelId());
serviceImpl.process(model);
modelService.update(model);
}
But when I'm trying to call this method I'm getting exception on line entities.add(entity);also the same exception occurs when I'm calling getEntities()on model.
I've checked transaction manager and it's configured correctly and transaction exists on this step. Also I've checked tons of answers on stackoverflow connected to this exception but nothing useful.
但是，当我试图调用这个方法我收到线异常entities.add(entity);，当我打电话时，也会发生同样的异常getEntities()上model。我已经检查了事务管理器，它配置正确，并且此步骤中存在事务。此外，我已经检查了与此异常相关的 stackoverflow 上的大量答案，但没有任何用处。
What could be the cause of it?
可能是什么原因造成的？
采纳答案by Maciej Kowalski
It seems that model is a detached entity.
似乎模型是一个独立的实体。
Try to merge and perform operations on a merge instance:
尝试在合并实例上合并和执行操作：
@Override
public void process(Model model) {
...
Model mergedModel = session.merge(model);
mergedModel.addEntity(createEntity());
...
}
回答by Orest
So as @Maciej Kowalski mentioned after first @Transactionalread of my modelit's already in deatached state and call to get entitiesfrom another @Transactionalmethod failed with LazyInitializationException.
因此，正如@Maciej Kowalski 在第一次@Transactional阅读我的文章后提到的那样，model它已经处于分离状态并且entities从另一个@Transactional方法中调用 get失败了LazyInitializationException。
I've changed my service a bit to get modelfrom database in the same transaction:
我已经改变了我的服务，以便model在同一个事务中从数据库中获取：
@Service
@Transactional
class ServiceImpl implements Service {
@Override
public void process(long modelId) {
...
Model model = modelDao.get(modelId);
model.addEntity(createEntity());
...
}
}
Now everything works as expected.
现在一切都按预期进行。
