Hi all,
I have 4 tables deal with 4 DAOs. But I have a funcion called search() that get infomation from 4 tables above. Will I put this function in which DAO ?.
I see each DAO work only on self table. such as searchBy..., delete, update. But a query complex we will put in which DAO ?
Thanks
> Hi all,
> I have 4 tables deal with 4 DAOs.
Usually DAOs map to objects, not tables, unless your objects also happen to map 1:1 with the tables.
> But I have a
> funcion called search() that get infomation from 4
> tables above. Will I put this function in which DAO
> ?.
If a single object can have JOINed information from four tables, with objects as data members, then you should have one object with the others as children and only write one DAO - the one for the parent.
If you were doing object/relational mapping, there would be one DAO and mappings for the 1:1, 1:m, and m:n relationships between the parent and its children.
> I see each DAO work only on self table. such as
> searchBy..., delete, update. But a query complex we
> will put in which DAO ?
You can have a separate Finder class that has complex queries if you need them.
%
Hi,
<<Will I put this function in which DAO ?>>
Your answer is no! DAO pattern is designed to solving jdbc spaghetti codes. and you did! what you need is not query from tables but is query from objects that you shoud implement this search in your bussiness logic. you can use "Business Object" pattern.
Regrads
Hi,
I mean : I have 4 table : A,B,C,D
and I wrote : ADAO, BDAO,CDAO,DDAO for each table
And now I have a query string like :
"select x,y,z
form A
INNER JOIN B ON ...
LEFT JOIN C ON...
LEFT JOIN D ON .."
wil I put this query in which DAO ? (ADAO, BDAO, CDAO,or DDAO ?)
> Hi,
> <<Will I put this function in which DAO ?>>
> Your answer is no! DAO pattern is designed to solving
> jdbc spaghetti codes. and you did! what you need is
> not query from tables but is query from objects that
> you shoud implement this search in your bussiness
> logic. you can use "Business Object" pattern.
> Regrads
I use a DAO per table. Thats what my DAOs are for. If one table changes I don't want to change 2-3 DAOs, just one.
I prefer this logic in a special DAO though. If you put it in a Business object, then you loose all the power of SQL.
Which in the end means if a table changes I have to change the appropriate DAO, plus any additional special DAOs as well. To be honest though I tend to mix this into one of the existing DAOs.
> > Hi,
> > <<Will I put this function in which DAO ?>>
> > Your answer is no! DAO pattern is designed to
> solving
> > jdbc spaghetti codes. and you did! what you need
> is
> > not query from tables but is query from objects
> that
> > you shoud implement this search in your bussiness
> > logic. you can use "Business Object" pattern.
> > Regrads
>
> I use a DAO per table. Thats what my DAOs are for.
> If one table changes I don't want to change 2-3
> DAOs, just one.
>
> I prefer this logic in a special DAO though. If you
> put it in a Business object, then you loose all the
> power of SQL.
>
Not to mention the speed.
> Hi all,
> I have 4 tables deal with 4 DAOs. But I have a
> funcion called search() that get infomation from 4
> tables above. Will I put this function in which DAO
> ?.
> I see each DAO work only on self table. such as
> searchBy..., delete, update. But a query complex we
> will put in which DAO ?
>
If you want a pattern for this then the Java Blueprints specifically has one for it.
If it was me I would just stick it someplace convenient though.
