One systematic way is to make a view that corresponds to each screen in the
application. Then make one entity bean for each view. Thus the database join is
in the db level and is hidden from both EB and application. However, it brings
up another question: how does EJB synchronize the cache with the underlying db
when more than one entity beans are modifying one physical table.
Lam
Pankaj Tandon wrote:
> The fact that you have defined an MxN relationship between AWARDS and
> PEOPLE means that you will eventually need to support a method such as
> Enumeration findPeopleForAward(Award a) ; in addition to
> findAwardsByPerson();
> If that is the case I think you will need an entity eJB called
> PersonAwardBean which implements *both* these business methods and is
> persisted in the PERSON_AWARD table.
>
> If however, you only need to implement findAwardsByPerson(); then you dont
> really need the PERSON_AWARD table. You will need a foreign key in the
> AWARDS table referecing the person table. (at db level, that's an option)
> and will need one entity eJB for each PERSON and AWARD table, most likely
> doing the 'join' in your session bean (The session bean will invoke finder
> methods on each bean). Unless someone can suggest how to write an entity
> bean for 2 tables connected by a foreign key....
>
> Shawn McKisson <[EMAIL PROTECTED]> on 10/14/99 12:40:55 PM
>
> Please respond to A mailing list for Enterprise JavaBeans development
> <[EMAIL PROTECTED]>
>
> To: [EMAIL PROTECTED]
> cc: (bcc: pankaj tandon/MIS/genco/US)
> Subject: I'm not understanding EBs.
>
> I am trying to build my first non-simple entity bean, however, I'm having
> some
> problems.
>
> What I have are people and awards.
> People is a simple table with only a "name" field and primary key.
> Awards is a simple table with only a "name" field and primary key.
>
> Since the relationship between people and awards is M x N, I have a
> relationship
> table which describes what people have which awards.
>
> My goal is to have an EB through which I can manipulate and view the people
> and
> their awards.
>
> My initial thought is to simply put a
>
> private Enumeration awards;
>
> as a instance variable of the PeopleBean. But I keep reading everywhere
> that an
> entity bean should represent 1 row of data from the data base. Placing this
> enumeration in the PeopleBean would mean that it represents n rows (1 for
> each
> award the person has won)
>
> The remote interface I would like to have for people is
>
> String getName();
> Enumeration getAwards();
>
> The fact that I want an enumeration of awards back makes me think that I
> should
> also have an Award EB that has a finder method suck as
> findAwardsByPerson();
>
> How should I handle this situation? Is creating an AwardBean the "proper"
> thing
> to do?
>
> --shawn
>
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