Hibernate and lazy loading sucks. Especially in Web Dynpro where we cannot use the Session in View pattern. Therefore there is handy method can load a collection to make sure that a collection is loaded and load it on demand from the service layer
public abstract class GenericDaoBean
// ....
public void initializeRelationship(T entity, String property) {
org.hibernate.Session session = getHibernateSession();
// the lock method adds the entity back into the Entitymanager makes it managed.
try {
session.lock(entity, LockMode.NONE);
Object collectionProxy = getAttributeValue(entity, property);
if(!Hibernate.isInitialized(collectionProxy))
{
Hibernate.initialize(collectionProxy);
}
} catch (TransientObjectException e) {
//ignore object that are not saved yet
}
}
public org.hibernate.Session getHibernateSession() {
Object delegate = getEntityManager().getDelegate();
org.hibernate.Session session = null;
//This is in SAP J2EE
if(delegate instanceof org.hibernate.Session){
session = (org.hibernate.Session) delegate;
}
// this is in OpenEJB container
else if(delegate instanceof HibernateEntityManager){
HibernateEntityManager hbEm = (HibernateEntityManager) delegate;
session = hbEm.getSession();
}
return session;
}
}
public static Object getAttributeValue(Object bean, String attributeName){
Map
PropertyDescriptor desc = props.get(attributeName);
if(desc == null) throw new IllegalArgumentException("attribute:" +attributeName + " does not exist in bean "+ bean);
try {
Object result = desc.getReadMethod().invoke(bean, null);
return result;
} catch (IllegalArgumentException e) {
throw new RuntimeException(e);
} catch (IllegalAccessException e) {
throw new RuntimeException(e);
} catch (InvocationTargetException e) {
throw new RuntimeException(e);
}
}
