RE: [JBoss-user] create(), ejbCreate() and id
It's generally more performant and robust for an enterprise database (oracle, db2, ms-sql, sybase, informix,...) to be generating the keys, they have been doing this for some time and are pretty well optimized. They generally support very inexpensive methods to get the new key value back (not re-qeurying the row just inserted) though the further along into this you get, the more proprietary it will be. It eliminates a second point of failure (if the database can't generate the key you probably can't insert the row anyways) but a separate bean could be unavailable even if the database is. One rub is that you in general cannot use these features with CMP beans because JAWS doesn't support it. I do this with BMP beans and a stored procedure (where supported) which allows me to write portable Java/JDBC code even if the implementation of the stored procedure is database specific. Cheers Jay -Original Message- From: David Jencks [mailto:[EMAIL PROTECTED]] Sent: Saturday, June 23, 2001 11:49 PM To: [EMAIL PROTECTED] Subject: Re: [JBoss-user] create(), ejbCreate() and id Hi, On 2001.06.23 18:11:57 -0400 [EMAIL PROTECTED] wrote: On Sat, Jun 23, 2001 at 11:25:32AM -0700, Konstantin Priblouda wrote: This interests me. I will be doing a project where I don't care much what the primary keys are, only that they are there and are unique (obviously). Ideally, I would have the database autogenerate a sequence of numbers, but there doesn't seem to be a way to get the Container to do this for me? Using database for it seems messy for me - you insert the row, and everything is fine (assumed your sequence or autonumbering worked), but getting this ID out of database is not convenient (and highly database dependent). That's why I prefer to use separate bean to generate ID's I seem to vaguely recall from when I used MS Access years ago that it had a special value type for auto-counter coloumns. You'd just define a coloumn and set it as a counter and everything happened automatically. It's something like this I'd want. It seems to me that this is a common thing to want to do and the database manager doing it would presumably be a lot more effecient than the application doing so. When I first encountered sequences/generators rather than autoincrement fields I shared your sentiments. However, using autoincrement fields has many problems, and is not necessarily faster. - You have to read the row again to find outs its only identifying characteristic. - There is often (depending on how thoughtless the implementation is) no way to copy these rows (into another table and back) and get meaningful results (you get a whole new set of ids, thus totally messing up foreign keys) - Using a sequence/generator can reduce db access (in the absence of triggers modifying the row you just inserted): you can get id's in large chunks and hand them out, only asking for more when you run out. davud jencks ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] create(), ejbCreate() and id
Jay Walters wrote: One rub is that you in general cannot use these features with CMP beans because JAWS doesn't support it. You can in limited ways: you're quite free to get a value from a sequence (Postgres or Oracle) within your ejbCreate code. I believe this is generally a pretty good comprimise. -danch ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] create(), ejbCreate() and id
--- danch (Dan Christopherson) [EMAIL PROTECTED] wrote: Jay Walters wrote: One rub is that you in general cannot use these features with CMP beans because JAWS doesn't support it. You can in limited ways: you're quite free to get a value from a sequence (Postgres or Oracle) within your ejbCreate code. I believe this is generally a pretty good comprimise. Which voids the very idea of CMP :) Why do I need it ( CMP ), if I still have to obtain connection and call something on database backend myself? regards, = Konstantin Priblouda ( ko5tik )Freelance Software developer http://www.pribluda.de play java games - http://www.yook.de render charts online - http://www.pribluda.de/povray/ __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail http://personal.mail.yahoo.com/ ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] create(), ejbCreate() and id
Konstantin Priblouda wrote: Which voids the very idea of CMP :) Why do I need it ( CMP ), if I still have to obtain connection and call something on database backend myself? This is one call, and it has the tremendous advantage that it will work. You're still not writing separate insert, update, delete, and one query per finder method. Also, BMP finders returning collections are very innefficient, whereas with CMP the container has the opportunity to optimize this. In JBoss 2.4, CMP collection finders are optimizable. ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] create(), ejbCreate() and id
if not db independent. I freely admit we do this all the time. we dont do it in the ejbCreate... we do it before calling create, but same difference. recently i had to write some components (really a set of beans/tags/jsps) that would work on (potentially) several databases... it was a little more difficult :) Al - Original Message - From: danch (Dan Christopherson) [EMAIL PROTECTED] To: [EMAIL PROTECTED] Sent: Monday, June 25, 2001 10:06 AM Subject: Re: [JBoss-user] create(), ejbCreate() and id You can in limited ways: you're quite free to get a value from a sequence (Postgres or Oracle) within your ejbCreate code. I believe this is generally a pretty good comprimise. -danch ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] create(), ejbCreate() and id
In a CD tutorial example I do not understand the role of id parameter in ejbCreate(String) method and who supplies this string and how. Is it the way EJB provides unique field for easy primary key implementation? Should I necessarily have such a field name in my bean and should I implement ejbCreate always with this signature? I am especially curious because I previously implemented non-argument ejbCreate() and got id is null failure message on deployment. Your EJB shall have primary key. ( and it could be whatever field you like ). On creation of your EJB you have to generate this key yourself. I use an separate bean as sequence generator. regards, = Konstantin Priblouda ( ko5tik )Freelance Software developer http://www.pribluda.de play java games - http://www.yook.de render charts online - http://www.pribluda.de/povray/ __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail http://personal.mail.yahoo.com/ ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] create(), ejbCreate() and id
Must add that you should be able to create Entity Beans without primary keys as well. As to what data they represent is obvious hence. Vinay - Original Message - From: Konstantin Priblouda Sent: Saturday, June 23, 2001 6:00 PM To: [EMAIL PROTECTED] Subject: Re: [JBoss-user] create(), ejbCreate() and In a CD tutorial example I do not understand the role of id parameter in ejbCreate(String) method and who supplies this string and how. Is it the way EJB provides unique field for easy primary key implementation? Should I necessarily have such a field name in my bean and should I implement ejbCreate always with this signature? I am especially curious because I previously implemented non-argument ejbCreate() and got "id is null" failure message on deployment.Your EJB shall have primary key. ( and it could bewhatever field you like ). On creation of your EJByou have to generate this key yourself.I use an separate bean as sequence generator.regards,=Konstantin Priblouda ( ko5tik ) Freelance Software developer http://www.pribluda.de play java games - http://www.yook.de render charts online - http://www.pribluda.de/povray/ __Do You Yahoo!?Get personalized email addresses from Yahoo! Mailhttp://personal.mail.yahoo.com/___JBoss-user mailing list[EMAIL PROTECTED]http://lists.sourceforge.net/lists/listinfo/jboss-userGet more from the Web. FREE MSN Explorer download : http://explorer.msn.com
Re: [JBoss-user] create(), ejbCreate() and id
On Sat, Jun 23, 2001 at 09:58:12AM -0700, Konstantin Priblouda wrote: Your EJB shall have primary key. ( and it could be whatever field you like ). On creation of your EJB you have to generate this key yourself. I use an separate bean as sequence generator. This interests me. I will be doing a project where I don't care much what the primary keys are, only that they are there and are unique (obviously). Ideally, I would have the database autogenerate a sequence of numbers, but there doesn't seem to be a way to get the Container to do this for me? Could you describe your sequence generator? It sounds like the thing that I need. Cheers Bent D -- Bent Dalager - [EMAIL PROTECTED] - http://www.pvv.org/~bcd powered by emacs ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] create(), ejbCreate() and id
This interests me. I will be doing a project where I don't care much what the primary keys are, only that they are there and are unique (obviously). Ideally, I would have the database autogenerate a sequence of numbers, but there doesn't seem to be a way to get the Container to do this for me? Using database for it seems messy for me - you insert the row, and everything is fine (assumed your sequence or autonumbering worked), but getting this ID out of database is not convenient (and highly database dependent). That's why I prefer to use separate bean to generate ID's Could you describe your sequence generator? It sounds like the thing that I need. I posted archive with complete source a week ago on the list (look in the archive). There is also ejbutil project on sourceforge ( they also have something like this ) And here is short outline what bean does: It has primary key ( string ID to locate it ), it has increment, current value and method getNext() which advances it. Whenever I need an ID, I lookup this bean by primary key ( I store value of this primary key as String data in ejb environment ), and then just call getNext() no magic, just some voodoo :) = Konstantin Priblouda ( ko5tik )Freelance Software developer http://www.pribluda.de play java games - http://www.yook.de render charts online - http://www.pribluda.de/povray/ __ Do You Yahoo!? Get personalized email addresses from Yahoo! Mail http://personal.mail.yahoo.com/ ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] create(), ejbCreate() and id
On Sat, Jun 23, 2001 at 11:25:32AM -0700, Konstantin Priblouda wrote: This interests me. I will be doing a project where I don't care much what the primary keys are, only that they are there and are unique (obviously). Ideally, I would have the database autogenerate a sequence of numbers, but there doesn't seem to be a way to get the Container to do this for me? Using database for it seems messy for me - you insert the row, and everything is fine (assumed your sequence or autonumbering worked), but getting this ID out of database is not convenient (and highly database dependent). That's why I prefer to use separate bean to generate ID's I seem to vaguely recall from when I used MS Access years ago that it had a special value type for auto-counter coloumns. You'd just define a coloumn and set it as a counter and everything happened automatically. It's something like this I'd want. It seems to me that this is a common thing to want to do and the database manager doing it would presumably be a lot more effecient than the application doing so. Could you describe your sequence generator? It sounds like the thing that I need. I posted archive with complete source a week ago on the list (look in the archive). There is also ejbutil project on sourceforge ( they also have something like this ) Thanks. Cheers Bent D -- Bent Dalager - [EMAIL PROTECTED] - http://www.pvv.org/~bcd powered by emacs ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
Re: [JBoss-user] create(), ejbCreate() and id
Hi, On 2001.06.23 18:11:57 -0400 [EMAIL PROTECTED] wrote: On Sat, Jun 23, 2001 at 11:25:32AM -0700, Konstantin Priblouda wrote: This interests me. I will be doing a project where I don't care much what the primary keys are, only that they are there and are unique (obviously). Ideally, I would have the database autogenerate a sequence of numbers, but there doesn't seem to be a way to get the Container to do this for me? Using database for it seems messy for me - you insert the row, and everything is fine (assumed your sequence or autonumbering worked), but getting this ID out of database is not convenient (and highly database dependent). That's why I prefer to use separate bean to generate ID's I seem to vaguely recall from when I used MS Access years ago that it had a special value type for auto-counter coloumns. You'd just define a coloumn and set it as a counter and everything happened automatically. It's something like this I'd want. It seems to me that this is a common thing to want to do and the database manager doing it would presumably be a lot more effecient than the application doing so. When I first encountered sequences/generators rather than autoincrement fields I shared your sentiments. However, using autoincrement fields has many problems, and is not necessarily faster. - You have to read the row again to find outs its only identifying characteristic. - There is often (depending on how thoughtless the implementation is) no way to copy these rows (into another table and back) and get meaningful results (you get a whole new set of ids, thus totally messing up foreign keys) - Using a sequence/generator can reduce db access (in the absence of triggers modifying the row you just inserted): you can get id's in large chunks and hand them out, only asking for more when you run out. davud jencks ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
[JBoss-user] create(), ejbCreate() and id
In a CD tutorial example I do not understand the role of id parameter in ejbCreate(String) method and who supplies this string and how. Is it the way EJB provides unique field for easy primary key implementation? Should I necessarily have such a field name in my bean and should I implement ejbCreate always with this signature? I am especially curious because I previously implemented non-argument ejbCreate() and got id is null failure message on deployment. ___ JBoss-user mailing list [EMAIL PROTECTED] http://lists.sourceforge.net/lists/listinfo/jboss-user
