我得到以下异常:
Exception in thread "main" org.hibernate.LazyInitializationException: could not initialize proxy - no Session
at org.hibernate.proxy.AbstractLazyInitializer.initialize(AbstractLazyInitializer.java:167)
at org.hibernate.proxy.AbstractLazyInitializer.getImplementation(AbstractLazyInitializer.java:215)
at org.hibernate.proxy.pojo.javassist.JavassistLazyInitializer.invoke(JavassistLazyInitializer.java:190)
at sei.persistence.wf.entities.Element_$$_jvstc68_47.getNote(Element_$$_jvstc68_47.java)
at JSON_to_XML.createBpmnRepresantation(JSON_to_XML.java:139)
at JSON_to_XML.main(JSON_to_XML.java:84)
当我尝试从以下几行拨打电话时:
Model subProcessModel = getModelByModelGroup(1112);
System.out.println(subProcessModel.getElement().getNote());
我getModelByModelGroup(int modelgroupid)
首先实现了这样的方法:
public static Model getModelByModelGroup(int modelGroupId, boolean openTransaction) {
Session session = SessionFactoryHelper.getSessionFactory().getCurrentSession();
Transaction tx = null;
if (openTransaction) {
tx = session.getTransaction();
}
String responseMessage = "";
try {
if (openTransaction) {
tx.begin();
}
Query query = session.createQuery("from Model where modelGroup.id = :modelGroupId");
query.setParameter("modelGroupId", modelGroupId);
List<Model> modelList = (List<Model>)query.list();
Model model = null;
for (Model m : modelList) {
if (m.getModelType().getId() == 3) {
model = m;
break;
}
}
if (model == null) {
Object[] arrModels = modelList.toArray();
if (arrModels.length == 0) {
throw new Exception("Non esiste ");
}
model = (Model)arrModels[0];
}
if (openTransaction) {
tx.commit();
}
return model;
} catch(Exception ex) {
if (openTransaction) {
tx.rollback();
}
ex.printStackTrace();
if (responseMessage.compareTo("") == 0) {
responseMessage = "Error" + ex.getMessage();
}
return null;
}
}
并得到了例外。然后一位朋友建议我始终测试该会话并获取当前会话,以避免出现此错误。所以我这样做:
public static Model getModelByModelGroup(int modelGroupId) {
Session session = null;
boolean openSession = session == null;
Transaction tx = null;
if (openSession) {
session = SessionFactoryHelper.getSessionFactory().getCurrentSession();
tx = session.getTransaction();
}
String responseMessage = "";
try {
if (openSession) {
tx.begin();
}
Query query = session.createQuery("from Model where modelGroup.id = :modelGroupId");
query.setParameter("modelGroupId", modelGroupId);
List<Model> modelList = (List<Model>)query.list();
Model model = null;
for (Model m : modelList) {
if (m.getModelType().getId() == 3) {
model = m;
break;
}
}
if (model == null) {
Object[] arrModels = modelList.toArray();
if (arrModels.length == 0) {
throw new RuntimeException("Non esiste");
}
model = (Model)arrModels[0];
if (openSession) {
tx.commit();
}
return model;
} catch(RuntimeException ex) {
if (openSession) {
tx.rollback();
}
ex.printStackTrace();
if (responseMessage.compareTo("") == 0) {
responseMessage = "Error" + ex.getMessage();
}
return null;
}
}
}
但仍然会出现相同的错误。我已经阅读了很多有关此错误的内容,并找到了一些可能的解决方案。其中之一是将lazyLoad设置为false,但是不允许这样做,因此建议我控制会话