RE: How to combine two non-decomposed m:n mappings in one collection?
Hi, Did you see my response to your other post? Please reply to the list. Cheers, Rob :) -Original Message- From: Patrick Scheuerer [mailto:[EMAIL PROTECTED] Sent: Tuesday, 6 January 2004 10:17 a.m. To: OJB Users List Subject: How to combine two non-decomposed m:n mappings in one collection? Hi, I have the following problem: I have a table keywords which has two non-decomposed m:n mappings to the tables document and file. The latter two both implement the interface SupportItem. In my Keyword class i would like to have a collection of all SupportItems for this keyword. Is it possible to declare two indirection-tables in a collection-descriptor? If not, how could this be accomplished? Can OJB handle such a case? Thanks a lot! Patrick - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] ---BeginMessage--- Hi Patrick. Is the field doc_id in download_pal_model actually meant to be model_id? Otherwise I am a touch confused :) Also, I assume you've checked out the advanced O/R mapping stuff at http://db.apache.org/ojb/tutorial3.html - if not, do it now! Idea #1: For download - model class-descriptor class=download table=t_download ... Field Descriptors ... collection-descriptor name=models element-class-ref=pal_model indirection-table=t_download_pal_model fk-pointing-to-this-class column=download_id/ fk-pointing-to-element-class column=model_id/ /collection-descriptor /class-descriptor And going from model - download... class-descriptor class=model table=t_model ... Field Descriptors ... collection-descriptor name=downloads element-class-ref=download indirection-table=t_download_pal_model fk-pointing-to-this-class column=model_id/ fk-pointing-to-element-class column=download_id/ /collection-descriptor /class-descriptor Okay, that's a simple non-decomposed M:N and you probably know that already ... That doesn't really help with the single-collection issue at all. Idea #2: How about: class-descriptor class=SupportItemI extent-class class-ref=Document/ extent-class class-ref=Download/ /class-descriptor class-descriptor class=pal_model table=t_pal_model ... Field Descriptors ... collection descriptor name=collectionOfSupportItemIs element-class-ref=SupportItemI indirection-table=t_pal_model_supportitems fk-pointing-to-this-class column=model_id/ fk-pointing-to-element-class column=SupportItemID/ /collection-descriptor /class-descriptor class-descriptor class=download table=t_download ... Field Descriptors ... collection-descriptor name=models element-class-ref=pal_model indirection-table=t_download_pal_model fk-pointing-to-this-class column=SupportItemID/ fk-pointing-to-element-class column=model_id/ /collection-descriptor /class-descriptor You should be able to keep your object design the same and just modify the tables a bit so there is one table for both relations... Still non-decomposed :) #3: Implement pal_model_download and pal_model_document as classes, extending a common class (ModelContents). Then ... class-descriptor class=ModelContents extent-class class-ref=pal_model_download/ extent-class class-ref=pal_model_document/ /class-descriptor class-descriptor class=pal_model table=t_pal_model ... Field Descriptors ... collection descriptor name=collectionOfSupportItemIs element-class-ref=ModelContents inverse-foreignkey field-ref=model_id/ /collection-descriptor /class-descriptor class-descriptor class=download table=t_download ... Field Descriptors ... collection-descriptor name=Models element-class-ref=pal_model_download inverse-foreignkey field-ref=download_id/ /collection-descriptor /class-descriptor class-descriptor class=pal_model_download table=t_pal_model_download field-descriptor name=model_id ... / field-descriptor name=download_id ... / reference-descriptor name=download class-ref=download foreignkey field-ref=download_id/ /reference-descriptor reference-descriptor name=model class-ref=model foreignkey field-ref=model_id/ /reference-descriptor /class-descriptor This will make the object model a bit harder, since model.collectionOfSupportItemIs will return ModelContent objects, not actual Downloads/Documents (i.e decomposed M:N) but you can keep the existing table stuff. Others may have better ideas :) Good Luck, Rob :) -Original Message- From: Patrick Scheuerer [mailto:[EMAIL PROTECTED] Sent: Friday, 2 January 2004 2:56 p.m. To: OJB Users List Subject: Mapping Question Hi, Please see the attached image of my data model for reference (I'm sorry for the attachment but it's kind of complicated to describe the
Re: How to combine two non-decomposed m:n mappings in one collection?
Coup, Robert Muir wrote: Hi, Did you see my response to your other post? Please reply to the list. No I didn't, sorry! I somehow gave up on this post... Idea #2: How about: class-descriptor class=SupportItemI extent-class class-ref=Document/ extent-class class-ref=Download/ /class-descriptor class-descriptor class=pal_model table=t_pal_model ... Field Descriptors ... collection descriptor name=collectionOfSupportItemIs element-class-ref=SupportItemI indirection-table=t_pal_model_supportitems fk-pointing-to-this-class column=model_id/ fk-pointing-to-element-class column=SupportItemID/ /collection-descriptor /class-descriptor class-descriptor class=download table=t_download ... Field Descriptors ... collection-descriptor name=models element-class-ref=pal_model indirection-table=t_download_pal_model fk-pointing-to-this-class column=SupportItemID/ fk-pointing-to-element-class column=model_id/ /collection-descriptor /class-descriptor You should be able to keep your object design the same and just modify the tables a bit so there is one table for both relations... Still non-decomposed :) This sounds interesting. Just let me make sure I got it right: I have to create a new table t_download_supportitemI which has a m:n mappings to t_download and and one to t_document (pretty much a replacement for t_pal_model) and t_pal_model has a 1:n mapping to t_pal_model_supportitemI... is that correct? Thank you very much for your detailed examples! Patrick - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: How to combine two non-decomposed m:n mappings in one collection?
Hi, This sounds interesting. Just let me make sure I got it right: I have to create a new table t_download_supportitemI which has a m:n mappings to t_download and and one to t_document (pretty much a replacement for t_pal_model) Well, I would call it t_pal_model_supportitemI, and its a replacement for t_pal_model_document AND t_pal_model_download and t_pal_model has a 1:n mapping to t_pal_model_supportitemI... is that correct? That was the idea. OJB _should_ be able to figure it out based on the extents and retrieve the document/download from the correct table. One fix (which is probably why you got confused): class-descriptor class=download table=t_download ... Field Descriptors ... collection-descriptor name=models element-class-ref=pal_model indirection-table=t_pal_model_supportitems fk-pointing-to-this-class column=SupportItemID/ fk-pointing-to-element-class column=model_id/ /collection-descriptor /class-descriptor Tell us how you get on. Rob :) - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: How to combine two non-decomposed m:n mappings in one collection?
Coup, Robert Muir wrote: Well, I would call it t_pal_model_supportitemI, and its a replacement for t_pal_model_document AND t_pal_model_download I guess that's what I wanted to say :-) Tell us how you get on. To remove any potential for misunderstanding (and since I'm a visual person :-)) I uploaded a new version of the data model picture: http://homepage.hispeed.ch/tabalooga/datamodel-redesign.jpg Patrick - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: How to combine two non-decomposed m:n mappings in one collection?
As you can see on the picture i adopted your t_ prefix for tables :-) It makes the repository.xml a lot easier to read! I hope you don't have a copyright on it ;-) I will let you know how I get along. Thanks again! Patrick - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: How to combine two non-decomposed m:n mappings in one collection?
Hi, As you can see on the picture i adopted your t_ prefix for tables :-) It makes the repository.xml a lot easier to read! I hope you don't have a copyright on it ;-) Yes. Well, I also got sick of playing with tables named 'user' and 'group' in projects - they need to be specified as '[user]' and '[group]' in SQL for a number of dbms'... To remove any potential for misunderstanding (and since I'm a visual person :-)) I uploaded a new version of the data model picture: http://homepage.hispeed.ch/tabalooga/datamodel-redesign.jpg Hmmm... now I'm confused again. :) Ah, you snuck in some other changes - keyword now relates to pal_model? Or maybe not... *** Assuming you want keyword and pal_model separate *** There's no need to define SupportItemI as a class with a table since it has no fields. It just tells OJB that Document and Download are related and can be referred to by other persistent classes as a SupportItemI Now ignoring role, category, user_role, and user: Tables required: T_download T_document T_pal_model T_pal_model_supportitem T_keyword_supportitem Java Classes required: SupportItemI Interface Download (implements SupportItemI) Document (implements SupportItemI) Pal_model Keyword OJB Repository: class-descriptor class=SupportItemI extent-class class-ref=document/ extent-class class-ref=download/ /class-descriptor class-descriptor class=pal_model table=t_pal_model ... Field Descriptors ... collection descriptor name=collectionOfSupportItemIs element-class-ref=SupportItemI indirection-table=t_pal_model_supportitems fk-pointing-to-this-class column=model_id/ fk-pointing-to-element-class column=SupportItemID/ /collection-descriptor /class-descriptor class-descriptor class=keyword table=t_keyword ... Field Descriptors ... collection descriptor name=collectionOfSupportItemIs element-class-ref=SupportItemI indirection-table=t_keyword_supportitems fk-pointing-to-this-class column=keyword_id/ fk-pointing-to-element-class column=SupportItemID/ /collection-descriptor /class-descriptor class-descriptor class=download table=t_download ... Field Descriptors ... collection-descriptor name=models element-class-ref=pal_model indirection-table=t_pal_model_supportitems fk-pointing-to-this-class column=SupportItemID/ fk-pointing-to-element-class column=model_id/ /collection-descriptor collection-descriptor name=keywords element-class-ref=keyword indirection-table=t_keyword_supportitems fk-pointing-to-this-class column=SupportItemID/ fk-pointing-to-element-class column=keyword_id/ /collection-descriptor /class-descriptor class-descriptor class=document table=t_document ... Field Descriptors ... collection-descriptor name=models element-class-ref=pal_model indirection-table=t_pal_model_supportitems fk-pointing-to-this-class column=SupportItemID/ fk-pointing-to-element-class column=model_id/ /collection-descriptor collection-descriptor name=keywords element-class-ref=keyword indirection-table=t_keyword_supportitems fk-pointing-to-this-class column=SupportItemID/ fk-pointing-to-element-class column=keyword_id/ /collection-descriptor /class-descriptor -Original Message- From: Patrick Scheuerer [mailto:[EMAIL PROTECTED] Sent: Tuesday, 6 January 2004 11:38 a.m. To: OJB Users List Subject: Re: How to combine two non-decomposed m:n mappings in one collection? Coup, Robert Muir wrote: Well, I would call it t_pal_model_supportitemI, and its a replacement for t_pal_model_document AND t_pal_model_download I guess that's what I wanted to say :-) Tell us how you get on. To remove any potential for misunderstanding (and since I'm a visual person :-)) I uploaded a new version of the data model picture: http://homepage.hispeed.ch/tabalooga/datamodel-redesign.jpg Patrick - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: How to combine two non-decomposed m:n mappings in one collection?
Coup, Robert Muir wrote: Hmmm... now I'm confused again. :) Ah, you snuck in some other changes - keyword now relates to pal_model? Or maybe not... *** Assuming you want keyword and pal_model separate *** The scenario is this: a PalModel should have a collection of SupportItemsI and a Keyword should have a collection of support items. Keyword doesn't relate to pal_model. Something else just came to my mind: a category should also have a collection of SupportItemsI... h. now it get's tricky... I'm going through your answer now... Patrick - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: How to combine two non-decomposed m:n mappings in one collection?
... and now for something completely different: do i even have define foreign key constraints in my database??? I'm having the impression that OJB is handling all the joins. Is it enough to have some loose tables in my DB ??? Patrick - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: How to combine two non-decomposed m:n mappings in one collection?
... and now for something completely different: do i even have define foreign key constraints in my database??? I'm having the impression that OJB is handling all the joins. Is it enough to have some loose tables in my DB ??? Well, it's up to you. OJB can and will do it anyway. If you want to use the database from somewhere else (ie. Not going through OJB - maybe direct JDBC or whatever) then it is probably a good idea so your data doesn't get screwed up (which will then confuse OJB). :) Rob :) - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: How to combine two non-decomposed m:n mappings in one collection?
The scenario is this: a PalModel should have a collection of SupportItemsI and a Keyword should have a collection of support items. Keyword doesn't relate to pal_model. Okay. So what was in my last email should work :) Something else just came to my mind: a category should also have a collection of SupportItemsI... h. now it get's tricky... class-descriptor class=category table=t_category ... Fields ... collection-descriptor name=collectionOfSupportItemIs element-class-ref=SupportItemI foreignkey-fieldref=category_id/ /collection-descriptor /class-descriptor And in download if you want to be able to navigate to category using a 'myCategory' field (if you only want to navigate from category to download, don't worry) class-descriptor class=download table=t_download ... Fields including 'category_id' ... ... Other collections for model/keywords ... reference-descriptor name=myCategory class-ref=category foreignkey field-ref=category_id/ /reference-descriptor /class-descriptor And similarly for document and role if you need it... Rob :) - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
RE: How to combine two non-decomposed m:n mappings in one collection?
One more important thing. Make sure your primary keys are unique across Documents _and_ Downloads. Ie. If there is document #10 there should never be download #10 This is because they are in the same extent. If you retrieve a collection of SupportItemI's then they need to have unique IDs, or a Bad Thing(TM) will occur. Depending on your DBMS, you can do this in a number of ways. http://db.apache.org/ojb/sequencemanager.html explains it. Set the same sequence-name for the primary key fields for all classes in an extent (download and document). Rob :) -Original Message- From: Patrick Scheuerer [mailto:[EMAIL PROTECTED] Sent: Tuesday, 6 January 2004 12:35 p.m. To: OJB Users List Subject: Re: How to combine two non-decomposed m:n mappings in one collection? ... and now for something completely different: do i even have define foreign key constraints in my database??? I'm having the impression that OJB is handling all the joins. Is it enough to have some loose tables in my DB ??? Patrick - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED] - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: How to combine two non-decomposed m:n mappings in one collection?
Thank you very much for your time and effort Robert! I'm trying to get your solution to work now (keep your fingers crossed! :-) ) Since this is all for my thesis paper you will get an honorable mention in the acknowledgment section :-) Thanks again and I'll let you know If it works! Take care, Patrick - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
