I don't know the correctness of this Dao pattern

[kongdx]

few days ago , a friend tell me a Dao pattern , but I don't know whether it can use in the production.
give me some suggestion please.

1 create a BaseDao extends HibernateDaoSupport

public class BaseDao extends HibernateDaoSupport{

private Log log = LogFactory.getLog(getClass());

public Session openSession() {
return SessionFactoryUtils.getSession(getSessionFactory() , false);
}

public Object get(Class entityClass, Serializable id) throws DataAccessException {
Session session = openSession();
try {
return session.get(entityClass, id);
}catch (HibernateException ex) {
throw SessionFactoryUtils.convertHibernateAccessExceptio n(ex);
}
}
.........
}

2 create EntityDao extends BaseDao

public interface EntityDao {

public Object get(Class entityClass, Serializable id) throws DataAccessException;

public Object load(Class entityClass, Serializable id) throws DataAccessException;
......
}

//Extends BaseDao and implements EntityDao interface
public class EntityDaoImpl extends BaseDao implements EntityDao{

}

3 create a EntityManager and use AOP pattern

public interface EntityManager {

public Object get(Class entityClass, Serializable id);

public Object load(Class entityClass, Serializable id);
......
}

public class EntityManagerImpl implements EntityManager {

private EntityDao entityDao;

public void setEntityDao(EntityDao entityDao) {
this.entityDao = entityDao;
}

public Object get(Class entityClass, Serializable id) {
return entityDao.get(entityClass, id);
}

public Object load(Class entityClass, Serializable id) {
return entityDao.load(entityClass, id);
}
......
}

so we implements a common hibernate entity operate engine

4 other BusinessService extends EntityManager

He tell me the reason is can fast create BusinessService and with few code to write.

[irbouho]

1. This is exactely what HibernateDaoSupport / HibernateTemplate are for!!!
1.1 logger

private Log log = LogFactory.getLog(getClass());

HibernateDaoSupport already has a logger that logs messages for current class, you do not need to use a new one.

1.2 session initialisation

public Session openSession() {
return SessionFactoryUtils.getSession(getSessionFactory() , false);
}

This is not necessary, you need to inject the HibernateSessionFactory into your DAO using Spring IoC and then use

getHibernateTemplate()

Spring will take care of Hibernate Session initialisation.

1.3 "base" methods

public Object get(Class entityClass, Serializable id) throws DataAccessException {
Session session = openSession();
try {
return session.get(entityClass, id);
}catch (HibernateException ex) {
throw SessionFactoryUtils.convertHibernateAccessExceptio n(ex);
}
}
.........

All of those methods are already taken care of by HibernateTemplate. Please review the javadoc.

2. DAO implementations
Basically, you should not pass the Entity.class as a parameter to a DAO that manages the Entity class!!! You should instead create higher level method that manage the Entity instances using some primary keys / criteria. In some cases, you can add specific data validation into the Dao layer so as it can be reusable by higher level layers (services).

3. idem

4. other BusinessService extends EntityManager (idem)
When calling a ProductManger from a web controller to get a specific product you will use

Product product = (Product) productManager.get(Product.class, new Long(123));

I really prefer this version:

Product product = productManager.get(new Long(123));

less verbose, more specialized and no casting!!!!

HTH

[kongdx]

thanks for your answer

1.1 I understand

1.2:
getHibernateTemplate();

the hibernateTemplate is so simple
for exapmle:
public abstract List find(int fristResult,int maxResults,String queryName);
the hibernateTemplate cannot implements it

1.3:
I think it is a Template pattern

2:
I think your meaning is :
each bo(business object) has only a independent dao
for example:
BusinessObject1 use dao1
and
BusinessObject2 use dao2

so in some cases, can add specific data validation into the Dao layer so as it can be reusable by higher level layers (services).

is it ?

[irbouho]

1.2:
getHibernateTemplate();

the hibernateTemplate is so simple
for exapmle:
public abstract List find(int fristResult,int maxResults,String queryName);
the hibernateTemplate cannot implements it

You can extend HibernateTemplate to implement it yourself or fill a request on JIRA.

I think your meaning is :
each bo(business object) has only a independent dao
for example:
BusinessObject1 use dao1
and
BusinessObject2 use dao2

so in some cases, can add specific data validation into the Dao layer so as it can be reusable by higher level layers (services).

is it ?

Yes

[puffybsd]

Or as mentioned, extend HibernateDaoSupport, and wrap a function around
getHibernateTemplate().executeFind(...):

public List find(final int firstResult, final int maxResults) {
 return getHibernateTemplate().executeFind(new HibernateCallback() {
  public Object doInHibernate(Session session) throws HibernateException,
   SQLException {
    Query query = session.createQuery(sql);
    query.setFirstResult(firstResult);
    query.setMaxResults(maxResults);
    return query.list();
  }
 }
}

Super-easy. Yeah, it might be nice if HibernateTemplate had firstResult, maxResults, but it's easy enough to implement and it would require adding a signature for every find method supported in HibernateTemplate including .findByNamedParam et al.
[/b]