Custom Finders

Question

Is it possible to implement a finder that achieves "Select from myTable where id1='abc' and id2='def' and id3='ghi'" The number of arguments in where being variable (i.e 1 to 3).
I tried using a finder with the following EjbQL "SELECT OBJECT(p) FROM myTable AS p WHERE p.id1=?1 and p.id2=?2 and p.id3=?3" and only supplied the search criteria that i wanted but it didnt work.
I tried using the finder as follows and it didnt work:
find("abc" ,"" ,"") or
find("abc" ,"*", "")
Any suggestions on that??
Thanks

Answer 1

Greetings,
Is it possible to implement a finder that achieves
"Select from myTable where id1='abc' and id2='def' and
id3='ghi'" The number of arguments in where being
variable (i.e 1 to 3). Generally, "no". This is contrary to the Entity Bean specification:
"An [entity bean] defines one or more finder methods, one for each way to find an entity object or collection of entity objects...." - EJB 2.0 Spec., 9.5.2 (emphasis added).
Which, generally, is why it doesn't work in CMP... the container implementor is constrained by the specification to implement behaviour that is consistent, in this case, with the above...
I tried using a finder with the following EjbQL
"SELECT OBJECT(p) FROM myTable AS p WHERE p.id1=?1 and
p.id2=?2 and p.id3=?3" and only supplied the search
criteria that i wanted but it didnt work.The following is of additional relevance here:
"The arguments of a finder method are used by the entity bean implementation to locate the requested entity objects." - ibid.
Note the specific use of the term "entity object" in reference to what a finder attempts to locate. While Entity Bean instances must be populated ("loaded") from the resource against which they map, this is merely the means to an end ("enterprise data - 'entities' - representation"), and not the end itself ("resource mapping"). The specification is always careful not to denigrate Entity Beans into a semblance of "data accessors"...
I tried using the finder as follows and it didnt
work:
find("abc" ,"" ,"") or
find("abc" ,"*", "")As implied above, the reason this "does not work" is because, since all arguments are being used to locate the "requested entity object", no entity objects are found which match all search criteria. ;) IOW, either where "id1='abc' and id2='' and id3=''" or where "id1='abc' and id2='*' and id3=''".
Any suggestions on that??If you need CMP then I suggest that you: first, implement a finder for each search criterion; and, second, front your entity bean(s) with a (stateless) session bean, or other business adapter, which can accept the search data in variable form (e.g. as pairs in a HashMap), and call the appropriate finder method accordingly. However, it is noteworthy that in BMP the implementation of desired behaviour is (mostly) at the disrection of the bean coder... ;)
ThanksRegards,
Tony "Vee Schade" Cook