disable lazy loading via API?

js · **Joined:** Wed Jun 30, 2004 12:47 pm **Posts:** 7

I have a set of objects which all use lazy loading. However, I have to ship data from a server to to a client with an identical database in large batches. I think about using JSX (java serialization to xml) fot that. Having all lazy="false" is great - just fetch the root object an serialize it and I can send the whole stuff with a single call. Tried it and it worked like a charm.

I would like to keep lazy="true" as a default and switch off all lazy loading for those transfer jobs, but did not find a way to do it. Did I overlook something, isn't it possible at all or will such a feature come in later releases?

Best Regards,
Johann

christian · **Posted:** Wed Jun 30, 2004 1:16 pm

Usually, you override fetching strategies with HQL and Criteria queries. If you like to disable/enable some setting globally, you might rebuild the SessionFactory after modifying the metadata from the Configuration programatically. This is easier than it sounds, get all PersistentClass objects from Configuration (the API), loop over all collections and setLazy(true). Then, build a new SessionFactory from this Configuration.

This is acceptable for once-a-day batch operations, I think.

js · **Joined:** Wed Jun 30, 2004 12:47 pm **Posts:** 7

Thanks, that was what I was looking for.

agent613 · **Joined:** Wed Jul 07, 2004 12:52 pm **Posts:** 9

For my case, this won't work.

I also need to serialize the graph to send to the client (who does not necessarily have hibernate).

I have lazy="true" set for all my classes. Since I have many, many associations, setting lazy="false" will result in a db error since the resulting query involves more than the Oracle limit of 1000 columns. I need to have the data fetched for the entire graph, but association-by-association, not all in one query.

michael · **Posted:** Thu Jul 15, 2004 4:30 pm

Well, using ClassMetadata to walk the graph and call Hibernate.initialize() on everything should be a 50-liner probably.

shl · **Posted:** Fri Jul 16, 2004 3:11 am

Pardon, but what about eager fetching with join fetch and setFetchMode, there is thread where Christian explains that approach http://forum.hibernate.org/viewtopic.php?p=2208765.

If you use eager fetching you don't need to manipulate metadata in run-time for disabling lazy fetch.

--
Leonid

agent613 · **Joined:** Wed Jul 07, 2004 12:52 pm **Posts:** 9

I'm not quite sure how to use ClassMetaData to do this.
I can manually walk my object graph and call Hibernate.initialize() on everything, but I'd prefer a generic approach, so that this code doesn't have to change every time the object model does.

Can you point me to somewhere where this process is documented?

agent613 · **Joined:** Wed Jul 07, 2004 12:52 pm **Posts:** 9

More specifically, I'm not sure as to how to use the metadata graph to traverse the object graph.

I would like to write code that goes something like:

Code:

private void forceLoad(Object obj) throws HibernateException {
     Hibernate.initialize(obj);
     ClassMetadata md = sessionFactory().getClassMetadata(obj.getClass());
     for(int i=0; i < md.getPropertyTypes().length; i++) {
       Type t = md.getPropertyTypes()[i];
       if(t.isEntityType()) {
         Object assoc = //get the assoc. object
         forceLoad(assoc);
       } else if(t.isPersistentCollectionType()) {
         Collection coll = //get the assoc. collection
         Hibernate.initialize(coll);
           
         for(Iterator iter = coll.iterator; iter.hasNext();) {
              forceLoad(iter.next());
            }
       }
     }
  }

but as you can see I am not clear on how to use the metadata to tell me how to walk thew object graph.

agent613 · **Joined:** Wed Jul 07, 2004 12:52 pm **Posts:** 9

There is a method on AbstractEntityPersister, getGetters() , which perhaps I could use in the above code, like:

Code:

...
if(t.isEntityType()) {
         Object assoc = ((AbstractEntityPersister)md).getGetters() [i].get(obj);
         forceLoad(assoc);
} 
...

However, getGetters() is protected. Do I need to define my own persister in order to accomplish this?

skywish · **Joined:** Thu May 28, 2009 4:24 am **Posts:** 1

I'm a bit change forceLoad() method, for me it's looks like this:

Code:

    protected SessionFactory getSessionFactory() {
        Session session = (Session) entityManager.getDelegate();
        return session.getSessionFactory();
    }

    public boolean isSkipClass(Class clazz) {
        Class[] skippedClasses = new Class[]{
              // classes to skip
        };
        return Arrays.asList(skippedClasses).contains(clazz);
    }

    protected void forceLoad(Object entity) throws HibernateException {
        if (entity == null) {
            return;
        }

        if (isSkipClass(entity.getClass())) {
            return;
        }

        ClassMetadata classMetadata = getSessionFactory().getClassMetadata(
                entity.getClass()
        );

        if (classMetadata == null) {
            return;
        }

        Hibernate.initialize(entity);

        for (int i = 0, n = classMetadata.getPropertyNames().length; i<n; i++) {
            String propertyName = classMetadata.getPropertyNames()[i];
            Type type = classMetadata.getPropertyType(propertyName);

            if (type.isEntityType()) {
                Object subEntity = classMetadata.getPropertyValue(entity, propertyName, EntityMode.POJO);
                forceLoad(subEntity);

            } if (type.isCollectionType()) {
                Collection collection = (Collection) classMetadata.getPropertyValue(entity, propertyName, EntityMode.POJO);
                if (collection != null && collection.size() > 0) {
                    for (Object collectionItem : collection) {
                        forceLoad(collectionItem);
                    }
                }
            }
        }
    }

Import section:

Code:

import com.thoughtworks.xstream.XStream;
import org.hibernate.EntityMode;
import org.hibernate.Hibernate;
import org.hibernate.HibernateException;
import org.hibernate.Session;
import org.hibernate.SessionFactory;
import org.hibernate.collection.PersistentBag;
import org.hibernate.metadata.ClassMetadata;
import org.hibernate.type.Type;
import org.jboss.seam.ScopeType;
import org.jboss.seam.annotations.In;
import org.jboss.seam.annotations.Name;
import org.jboss.seam.annotations.Scope;

import javax.persistence.EntityManager;
import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.FileReader;
import java.io.FileWriter;
import java.io.Serializable;
import java.util.Arrays;
import java.util.Collection;

shekhar.hp · **Joined:** Mon Apr 23, 2012 7:45 am **Posts:** 1

hello Skywish,

it's very good thought to disable lazy loading.

but i have lazy="false" in hbm file and now I want enable lazy loading in programmatically without changing anything in hbm file.

Could you please suggest us and it could be better if you provide any example?

Thanks in advance!

regards,
shekhar reddy.