The "Design Patterns" section of the Wiki.....
jiesheng zhang
<jasonnew2001@ To: [EMAIL PROTECTED]
yahoo.com> cc:
Subject: Re: [Hibernate] Hibernate usage
question
11/02/03 05:07
PM
Hi,
gavin
I will very interested in this topic. Where can I find
the "open session in view" pattern documentation?
Thanks
--- [EMAIL PROTECTED] wrote:
>
> Check out the "open session in view" pattern for
> these kind of simple
> applications.
>
> The basic idea is to use a servlet filter to open
> and close sessions.
>
>
>
>
>
>
> Chris Conrad
>
>
> <[EMAIL PROTECTED]>
> To: [EMAIL PROTECTED]
>
> Sent by:
> cc:
>
>
> [EMAIL PROTECTED] Subject:
> [Hibernate] Hibernate usage question
>
> eforge.net
>
>
>
>
>
>
>
>
> 11/02/03 11:54 AM
>
>
>
>
>
>
>
>
>
>
>
>
> After reading the Hibernate documentation and
> contributed documentation,
> I have not seen any advice on how to best utilize
> Hibernate for this
> application.
>
> I'm currently working on a community based
> collaboration web
> application. The architecture is fairly basic, an
> MVC framework
> (probably Struts) for the web tier, local stateless
> session beans for
> the business tier and hibernate for the persistence
> layer. The problem
> I've run across is this application has many
> entities which are
> inter-related in a potentially large object graph.
> For example, a User
> is associated with 1 or more Communities. Each
> Community is associated
> with 1 or more Conversations. Each Conversation can
> have any number of
> Threads, etc.
>
> My question is, what is the best way to manage a
> large object graph like
> this? The first thought I had was to use lazy
> loading and proxies, but
> since the session is already closed by the time the
> data gets to the web
> tier, that doesn't work. The Lightweight Class
> pattern seems to
> partially solve the problem but leaves two issues
> unresolved:
>
> 1. It will require a large number of Lightweight
> Classes to avoid
> retrieving unnecessary data from the database. For
> example, the basic
> user information will be stored in the HttpSession.
> To get the
> Communities related to it, an object mapped just to
> the user's
> Communities relationship will be necessary. To get
> the Tasks assigned
> to them, an object mapped just to the users Tasks
> relationship will be
> necessary. Using a heavy weight class with proxies
> and lazy loading
> allows for only 1 object to be used, but then all of
> the data already
> stored in the user's session will be fetched as
> well, adding an extra
> query (1 query for the data I already have, 1 query
> to lazy load the
> data I actually want).
>
> 2. There doesn't appear to be any way to manage
> creating new
> relationships without at least 1 extra query. If I
> want to add a
> Conversation to a Community, I'll need to load the
> Community (at least 1
> query, 2 if using lazy loading) and then add the
> Conversation to the
> Community (a second query to update the join table).
>
> Unfortunately, I've been unable to find any
> documentation or examples
> that deal with a large object graph but are unable
> to use lazy loading
> and proxies because of the EJB layer. I'd be very
> grateful for any
> pointers to docs or examples that solve this
> problem. I'm sure I'm
> going about it from the complete wrong direction
> which is why I'm
> running into this issue in the first place.
>
> --Chris
>
>
>
>
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