25 Apr
2008
25 Apr
'08
11:59 a.m.
On Thu, Apr 24, 2008 at 8:59 PM, Sachin Mittal <sjmittal(a)gmail.com> wrote:
Classes can also have an entity relationship among themselves.
I have few question on how can we relate classes in xwiki. Let me start by
posting a simple example:
Say our application has two classes Product and Review. Relationship between
them is a product can have multiple reviews.
Now I can relate these classes in following way:
1. Create a product document and add the product object to it. All the
reviews for that product are also added to that product document as review
objects. Thus I have grouped reviews to a product.
This way is the simpliest one, cons :
- not scalable since document load/save speed depends on the number
of objects it holds.
- objects cannot be queried from the public API (meaning no ordering
on field values for example)
- notifications (by email for example) are hard to write (which
object has been modified in this save ?)
2. Create a product document and add the product
object to it. For each
review for that product created a review document and add review object to
that review document and make review document child of product document.
Thus I have arranged reviews as children of a product.
Best way to do it imho, pros :
- scalable
- no need to create author, date, title, etc fields in your Review class
- methods needed to get relationships are already present in the
Document API (get childs, parent)
- allow complex queries like ordering the reviews by some criteria
(creation date, mod date, author, etc)
- easy to write fine-grained notifications (review
creation/modification/deletion)
3. In the review class add a db list field, which
refers to objects of
product class. While creating a review object choose the right product name
from the list. Thus reviews are associated to a product.
I've tried this in the past but I had some perf issues with the db
list displayer. It also appeared that choosing an item in a long list
when it was possible to imply the parent from the parent sheet wasn't
effective from the user POV. BTW this behavior can be emulated with
some custom parent displayer.
Hope this helps,
--
Jean-Vincent Drean