will try
Am 07.12.11 23:34, schrieb Rainer Döbele:
Hi Jens,
well, yes and no.
OO mappers usually work with bean that represent full entities.
In most queries I use (selecting items for display in a list e.g.) I don't need
a full entitiy.
In fact my tables usually have many columns and there is no point selecting
columns I don't need.
Instead I need a combination of fields from different tables and views.
So in your case with your query:
select A.name, B.whatever1, B.whatever2
I would expect to receive a List<QAB> where QAB is a class created
specifically for this query (I use nested classes a lot). E.g.
class QAB {
String name; // from table A
Object whatever1; // from table B
Ojbect whatever2; // from table B
...
// + Getters and Setters for all properties
}
Only in the detail view I normally need a full entitiy. But then I'd rather use
a DBRecord instead of a bean.
But there is always room to build something on top.
And if you feel that you have created something that could be interesting for a
greater audience, we would be grateful to receive and check your code and
possibly we would then add it to our code base. Apache is all about
contribution and getting new ideas in from other people.
Regards
Rainer
from: Jens Breitenstein [mailto:[email protected]]
to: [email protected]
re: Re: Bean handling in 1:n relationships or joins
Hi Rainer!
I know it's not a full blown oo mapper and that was exactly the reason
to give empire a chance after some painful hibernate experiences in
past
projects...
What about extending the getBeansList method to pass in a list of
classes to support an OO mapping for lets say one hierarchy?
Consider we have an entity A and B
A (name)
B (whatever1, whatever2, FK_to_A)
In case we select A.name, B.whatever1, B.whatever2 by a join it's
really
comfortable to operate on a list<object[A, B]> having all parameters
properly filled instead of an FK which requires an additional select
per
row?
I have not digged into the sources yet but I believe its not far from
what currently exists, or am I wrong? Maybe we can add it to a
XMas-Wishlist??
Jens
Btw: thanks for the quick response.
Am 07.12.11 18:41, schrieb Rainer Döbele:
Hi Jens,
remember that Empire-db is not an OR-Mapper and it does nothing
automatically.
In exchange it gives you more control over what, when and how
database operations are performed.
Even though beans can be used as data containers, they will not
provide the same level of functinality than a DBRecord does.
Again I recommend to take a look at our examples empire-db-example-
basic and empire-db-example-advanced.
Regards
Rainer
from: Jens Breitenstein [mailto:[email protected]]
to: [email protected]
re: Bean handling in 1:n relationships or joins
Hi all!
I have to admit I am pretty new to empire-db but feel quite
confortable
with it...
Finally I got the Bean mapping working for single tables and I now
get
stuck in how to handle joins correctly...
Assume a simple relationship between a document and a user (where
the
users-pk is part of the documents as fk to indicate a relation
"document
is owned by user").
Using the getBeanList method it seems only possible to convert a
"root"
element (in my case the document) but not any referenced element
automatically?
If I am wrong can someone explain me how I can retrieve a "document"
having a fully instantiated "user" element instead of just an FK?
Or do I have to read the user record manually and the bean handling
does
not support joined objects at all?
thanks in advance
Jens
