Re: JDO && OJB
JDO Central ( http://www.jdocentral.com/ ) is a good JDO starting point. The best source for info on JDOQL is the spec, it is actually pretty clear, I think ( http://jcp.org/aboutJava/communityprocess/pr/jsr243/index2.html ). OJB's JDO implementation is more proof-of-concept than production-usable. A good open source JDO implementation is JPOX ( http://www.jpox.org/ ). Before long there should be an Apache JDO ( http://wiki.apache.org/jdo/ )project which can use OJB as the O/R Mapping backend. -Brian On Mar 19, 2005, at 7:09 PM, Markus Wolf wrote: Are there any advanced tutorials for JDOQL available? Or has someone some links to good resources about JDOQL? Regards Markus Wolf -- emedia-solutions wolf Wedeler Landstrasse 63 22559 Hamburg (040) 550 083 70 web: http://www.emedia-solutions-wolf.de mail: [EMAIL PROTECTED] pgp: http://wwwkeys.de.pgp.net - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
JDO && OJB
Are there any advanced tutorials for JDOQL available? Or has someone some links to good resources about JDOQL? Regards Markus Wolf -- emedia-solutions wolf Wedeler Landstrasse 63 22559 Hamburg (040) 550 083 70 web: http://www.emedia-solutions-wolf.de mail: [EMAIL PROTECTED] pgp: http://wwwkeys.de.pgp.net signature.asc Description: OpenPGP digital signature
[ojb|jdo] Join query using jdo/ojb
Hello all, I was going through some documents related to JDOQL and I found that they have made the db-objects with other db-objects as attributes for maintaining foreign key relationship. Example: Employee object represents the Employee table in the database. It has a attribute department. Now the department itself is an db-object which represents the Department table. So they are able to use the api of JDO to make joins using setFilter. I checked some reversedb tools and they all make dbobjects with the id, instead of the object itself. Example: Employee object has an attribute named departmentid, instead of department itself. I understand that the mapping is done in repository_user.xml about the foreign key relationship. However, in the above scenario, it is not possible to make join query using setFilter as in JDO api. Please let me know if the second approach, of using the Id instead of object itself is correct. If it is correct, how to make join? Will I have to use the OJB API? Please help me in this regard. Thanks in advance. Regards, Vijay Sargunam Icicle Consultancy, Web: www.icicleconsultancy.com
Re: Re: JDO OJB bridge and object states
> Hello Thomas, > > This might have been my own fault. I fetched the an object within other > transaction and tried to set it to another object's field within another > transaction and then tried to persist the container object. This caused > a primary key violation because it was already in the database. OK! > All JDO > flags (pesistent, dirty, transient) seem to be false even after data has > just been fetched from database, which is weird. > > Is this expected behaviour? No, it's really an issue. there is already a thread regarding this issue on the mailinglist. I'm currently working on a fix for this problem. Objects loaded by OJB should show the right flags to user code ! cheers, Thomas > -Marko > > > > > I'm not aware of any shortcomings of the JDO stuff. > > please post a code sample to understand your problem. > > > > If there is a bug we'll have to fix it! > > > > > - > To unsubscribe, e-mail: [EMAIL PROTECTED] > For additional commands, e-mail: [EMAIL PROTECTED] > __ Spam-Filter fuer alle - bester Spam-Schutz laut ComputerBild 15-03 WEB.DE FreeMail - Deutschlands beste E-Mail - http://s.web.de/?mc=021120 - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: JDO OJB bridge and object states
Hello Thomas, This might have been my own fault. I fetched the an object within other transaction and tried to set it to another object's field within another transaction and then tried to persist the container object. This caused a primary key violation because it was already in the database. All JDO flags (pesistent, dirty, transient) seem to be false even after data has just been fetched from database, which is weird. Is this expected behaviour? -Marko I'm not aware of any shortcomings of the JDO stuff. please post a code sample to understand your problem. If there is a bug we'll have to fix it! - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Re: JDO OJB bridge and object states
Hi Marko, I'm not aware of any shortcomings of the JDO stuff. please post a code sample to understand your problem. If there is a bug we'll have to fix it! thanks, Thomas Marko Lahma wrote: Hi again! I've read earlier postings about JDO and it's state transitions (dirty, persistent, transient) and and OJB's shortcomings in this area of functionality. Is there any light ahead for this to work some day? I've found it quite impossible to update an object back to datastore because JDO sees these fetched objects as non persistent and therefore tries to add them into database which leads to primary key violation. Any workarounds, anything? -Marko - 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]
JDO OJB bridge and object states
Hi again! I've read earlier postings about JDO and it's state transitions (dirty, persistent, transient) and and OJB's shortcomings in this area of functionality. Is there any light ahead for this to work some day? I've found it quite impossible to update an object back to datastore because JDO sees these fetched objects as non persistent and therefore tries to add them into database which leads to primary key violation. Any workarounds, anything? -Marko - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
Seeking advice on switching JDO->OJB
Hello, I have build a prototype applicition using an evalution-version of a commercial JDO application. However, we'll get a commercial deployment much sooner than anticipated, there will be more developers than just me, and it seems better for us to use open-source products only. I get the impression that OBJ is most suited for our needs but I'm not sure yet how to switch. - How suitable is OBJ-JDO for commercial deployement, given it's dependancy on the sun-ri? - Using OBJ-JDO will give me the fastest transition-path, switching to OJB-ODMG API can happen a bit slower. However, where can I find documentation on the OBJ vender-extensions for the JDO metadata? - Is there any schema-generator for OJB? Or does OJB always map between existing schema and existing objects? (For me it's better if the implementation handles schema-generation!) - How does OJB handle ordering of data in java.util.Lists? Is the order in the list maintained upon loading from DB? (The various JDO implementations which I tried can maintain this order using an extra column in the table linking the sides of the m:n relationship). I need an easy way to maintain order of elements in a java.util.List field. - I'm currently using MySQL database, but will probably be using hsqldb in future because it's easier to set up on different systems when we don't have to share data yet. I think these are my most urgent questions for the moment. I'd appreciate any assistence. With regards, --Tim van der Leeuw - To unsubscribe, e-mail: [EMAIL PROTECTED] For additional commands, e-mail: [EMAIL PROTECTED]
