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作者	DAO該设计成什么粒度的？
gaoxt1983 发贴: 67 积分: 0	于 2006-05-28 14:24 是设计成getUserNameById(int id)还是GetUserById(int id)？还有select * from a,和select name from a有性能上的区别吗？ why edited on 2006-06-05 22:07

作者

Re:DAO改设计成什么粒度的？ [Re:gaoxt1983]

floater

Java Jedi

总版主

发贴: 3233
积分: 421

于 2006-06-05 21:18

should be loadUser(User user), where user is partially filled with whatever id you have before the load. The rest fields should be filled after the load.

never never use select * from, always always use select <concrete columns> from. The * could have a lot of side effects, say, order of columns, new columns, etc.

"Any fool can write code that a computer can understand. Good programmers write code that humans can understand."
- Martin Fowler, Refactoring - Improving the Design of Existing Code

作者

Re:DAO該设计成什么粒度的？ [Re:gaoxt1983]

gaoxt1983

发贴: 67
积分: 0

于 2006-06-06 14:42

Thank upstair, but I have another question, say, I write a DAO, has a method getUsers(int age,boolean sex,String firstName), how do I implement it? Does I implment it by write
{
ResultSet rs=stmt.execute(select firstName,surName,age,sex,detail from users);
//filter the rs
//return a list with the right entities
}

or use the following style:
if(age!=0)
stmtString+="where age="+age;
if(xxxx
xxxxxx

??????

作者	Re:DAO該设计成什么粒度的？ [Re:gaoxt1983]
floater Java Jedi 总版主发贴: 3233 积分: 421	于 2006-06-06 21:38 you need to convert your search to sql queries somehow(like your second way). You don't want to get a rs and filter that, because that's exactly what db/sql does, not java does best/fast. "Any fool can write code that a computer can understand. Good programmers write code that humans can understand." - Martin Fowler, Refactoring - Improving the Design of Existing Code

作者	Re:DAO該设计成什么粒度的？ [Re:gaoxt1983]
ftang 版主发贴: 214 积分: 38	于 2006-06-23 23:21 同学，你这个设计还根本没法谈到粒度的问题啊，俺觉得你应该先看看别人作的，然后再想想怎么弄～～给你个地方瞧瞧，你现在的写法还是上个世纪的水平阿 http://ibatis.apache.org/dao.html

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