Generic Data Access Objects 设计模式

 

/**
 * 这是针对IGenericDAO接口的Hibernate实现，完成通用的CRUD操作。
 * @author rainlife
 * @param  POJO类
 * @param   POJO类的主键标识符
 * @param  针对每一个POJO类的DAO类实现
 */
public abstract class GenericDAOHibernate 〈T,ID extends Serializable, DAOImpl extends IGenericDAO〈T,ID〉〉
        implements IGenericDAO〈T,ID〉
{
    private Class persistentClass;

    protected Session session;

    public GenericDAOHibernate()
    {
        this.persistentClass = (Class) ((ParameterizedType) getClass()
                .getGenericSuperclass()).getActualTypeArguments()[0];
    }

    @SuppressWarnings("unchecked")
    public DAOImpl setSession(Session s)
    {
        this.session = s;
        return (DAOImpl)this;
    }

    protected Session getSession()
    {
        if (session == null)
            throw new IllegalStateException(
                    "Session has not been set on DAO before usage");
        return session;
    }

    public Class getPersistentClass()
    {
        return persistentClass;
    }


    @SuppressWarnings("unchecked")
    public T findById(ID id)
    {
        return (T) getSession().load(getPersistentClass(), id);
    }

    @SuppressWarnings("unchecked")
    public T findById(ID id, boolean lock)
    {
        T entity;
        if (lock)
            entity = (T) getSession().load(getPersistentClass(), id, LockMode.UPGRADE);
        else
            entity = findById(id);

        return entity;
    }

    @SuppressWarnings("unchecked")
    public List findAll()
    {
        return findByCriteria();
    }

    @SuppressWarnings("unchecked")
    public List findByExample(T exampleInstance)
    {
        Criteria crit = getSession().createCriteria(getPersistentClass());
        Example example = Example.create(exampleInstance);
        crit.add(example);
        return crit.list();
    }

    @SuppressWarnings("unchecked")
    public List findByExample(T exampleInstance, String[] excludeProperty)
    {
        Criteria crit = getSession().createCriteria(getPersistentClass());
        Example example = Example.create(exampleInstance);
        for (String exclude : excludeProperty)
        {
            example.excludeProperty(exclude);
        }
        crit.add(example);
        return crit.list();
    }

    @SuppressWarnings("unchecked")
    public T makePersistent(T entity)
    {
        getSession().saveOrUpdate(entity);
        //getSession().save(entity);
        return entity;
    }

    public void makeTransient(T entity)
    {
        getSession().delete(entity);
    }

    @SuppressWarnings("unchecked")
    protected List findByCriteria(Criterion... criterion)
    {
        Criteria crit = getSession().createCriteria(getPersistentClass());
        for (Criterion c : criterion)
        {
            crit.add(c);
        }
        return crit.list();
    }

    @SuppressWarnings("unchecked")
    /**
     * 增加了排序的功能。
     */
    protected List findByCriteria(Order order,Criterion... criterion)
    {
        Criteria crit = getSession().createCriteria(getPersistentClass());
        for (Criterion c : criterion)
        {
            crit.add(c);
        }
        if(order!=null)
            crit.addOrder(order);
        return crit.list();
    }

    @SuppressWarnings("unchecked")
    protected List findByCriteria(int firstResult,int rowCount,Order order,Criterion... criterion)
    {
        Criteria crit = getSession().createCriteria(getPersistentClass());
        for (Criterion c : criterion)
        {
            crit.add(c);
        }
        if(order!=null)
            crit.addOrder(order);
        crit.setFirstResult(firstResult);
        crit.setMaxResults(rowCount);
        return crit.list();
    }
}

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