findByCriteria(...)应该怎么用？

Question

findByCriteria(...)应该怎么用？

public List findByCriteria(Criterion... criterion) {
return createCriteria(criterion).list();
}

这个方法应该怎么用？

比如表结构如下
id pk
money float
type_id fk

按照type_id分组求sum(money) 在dao里应该怎么写？

Answer 1

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
[code="java"]
public List findByCriteria(DetachedCriteria criteria) {
log.debug("finding DispatchTask instance by criteria");
try {
List 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;
}
}
[/code]
这是Service的片段
[code="java"]
public List 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);
}

[/code]

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