Java 中利用泛型和反射机制抽象DAO的实例

import java.io.Serializable;
import java.util.List;
public interface BaseDao<T> {
  T get(Serializable id);
  List<T> getAll();
// List<T> find(String hql,);
  void save(Object o);
  void remove(Object o);
  void update(Object o);
}

import java.io.Serializable;
import java.lang.reflect.ParameterizedType;
import java.lang.reflect.Type;
import java.util.List;
import org.springframework.orm.hibernate3.support.HibernateDaoSupport;
public class HibernateBaseDao<T> extends HibernateDaoSupport implements BaseDao<T>{
  private Class<T> entityClass;
  public HibernateBaseDao() {
    Type genType = getClass().getGenericSuperclass();
    Type[] params = ((ParameterizedType) genType).getActualTypeArguments();
    entityClass = (Class)params[0];
  }
  public T get(Serializable id) {
    return (T)getHibernateTemplate().load(entityClass, id);
  }
   public List<T> getAll() {
    return getHibernateTemplate().loadAll(entityClass);
  }
  public void save(Object o) {
    getHibernateTemplate().saveOrUpdate(o);
  }
  public void remove(Object o) {
    getHibernateTemplate().delete(o);
  }
  public void update(Object o) {
    getHibernateTemplate().update(o);    
  }
}

import java.util.Iterator;
import java.util.List;
import com.baobaotao.dao.ForumDao;
import com.baobaotao.dao.HibernateBaseDao;
import com.baobaotao.domain.Forum;
public class ForumHibernateDao2 extends HibernateBaseDao<Forum> implements ForumDao{
  public long getForumNum() {
    Iterator iter = getHibernateTemplate().iterate(
    "select count(f.forumId) from Forum f");
    return ((Long)iter.next());
  }
}