DetachedCriteria例子

首先这是Hibernate的QBC检索方式，建议baidu下QBC，或者看书和API。
下面是我写过的一个项目中的代码片段，这是DAO的片段

public List<DispatchTask> findByCriteria(DetachedCriteria criteria) {
    	log.debug("finding DispatchTask instance by criteria");
        try {
            List<DispatchTask> results = getHibernateTemplate().findByCriteria(criteria);
            log.debug("find by criteria successful, result size: " + results.size());
            return results;
        } catch (RuntimeException re) {
            log.error("find by criteria failed", re);
            throw re;
        }
    }

这是Service的片段

public List<DispatchTask> getByQuery(DispatchTask instance,
			Date queryTime1, Date queryTime2) {
		String taskId = instance.getTaskId();
		String deptName = instance.getDeptName();
		String linkman = instance.getLinkman();
		String plateNum = instance.getPlateNum();
		Short statusId = instance.getStatusId();
		Date queryTime3 = null;
		if(queryTime2 != null){
			queryTime3 = new Date();
			queryTime3.setTime(queryTime2.getTime()+(new Long("86400000")));
		}
		
		DetachedCriteria criteria = DetachedCriteria
				.forClass(DispatchTask.class);
		if (taskId != null && taskId != "") {
			criteria.add(Expression.like("taskId", taskId, MatchMode.ANYWHERE));
		}
		if (deptName != null && deptName != "") {
			criteria.add(Expression.like("deptName", deptName,
					MatchMode.ANYWHERE));
		}
		if (linkman != null && linkman != "") {
			criteria.add(Expression
					.like("linkman", linkman, MatchMode.ANYWHERE));
		}
		if (plateNum != null && plateNum != "") {
			criteria.add(Expression.like("plateNum", plateNum,
					MatchMode.ANYWHERE));
		}
		if (statusId != null && statusId != 999) {
			criteria.add(Expression.eq("statusId", statusId));
		}
		if (queryTime1 != null) {
			if(queryTime2 != null){
				if(queryTime1.getTime() <= queryTime2.getTime()){
					criteria.add(Expression.between("dispatchDate", queryTime1,
							queryTime3));
				}
			}else{
				criteria.add(Expression.ge("dispatchDate", queryTime1));
			}
		}else{
			if(queryTime2 != null){
				criteria.add(Expression.le("dispatchDate", queryTime3));
			}
		}
		
		return dispatchTaskDAO.findByCriteria(criteria);
	}

关键是给出规则，即Criterion，DetachedCriteria是继承它的。这个找个Hibernate的API就了解了。
至于您说的例子，DAO就是DatabaseAccessObject，我觉得您把逻辑放进DAO里是不是违反了面向对象的思想呢？我不喜欢这么设计

 

转自：http://www.iteye.com/problems/5628