There will also be holes if you set the step size to something greater than one. The key (npi) is that you are not interested in the value provided it is unique. Thus the hi-lo cache strategy whereby you keep a bunch of keys in memory retrived from a sequence in oracle, for example, and if something goes awry you toss the in memory values. Imapact: zero, not interested in what the values are only that we get a unique batch of keys next time around.
-----Original Message----- From: wonder sonic [mailto:[EMAIL PROTECTED] Sent: Wednesday, March 19, 2003 2:47 AM To: [EMAIL PROTECTED] Subject: Re: Re[2]: [JBoss-user] CMP - Primary Key Strategies? Note that Oracle sequences can't be rollbacked! If you encounter any Exception (NullPointer...), there'll be a hole. Cheers, WS --- costin <[EMAIL PROTECTED]> a �crit�: > Hi! > > So basically you can use the autoincrement feature > with: > > - not doing anything in ejbCreate > > (the rest is standard - get/set > methods/descriptor/etc...)? > > Is this correct? > > > BS> Hi Eric > BS> Well this is good to used db based > sequence number as the primary key . I m currently > using the mysql and its auto_increment sequence as > primary key > BS> But to use this feature u have to use jboss > 3.2.03 beta ..As unique sequence no is managed by > the db not but the EJB container . so while inserted > the new record . u dont have to pass the value > BS> for the unique sequence no. > BS> Like u have a User Entity EJB > BS> User have DB schema > > BS> userID int(11) auto_increment primary key > ----------------------- now this is acting as the > primary key > BS> username varchar(30) > BS> password varchar(30) > BS> email varchar(30) > BS> ur > > BS> ejbCreate(String username, String password, > String email) > BS> { > BS> // here u havent provided the value of > userID as it inserted by DB // it can any sequence > no > BS> } > BS> ejbPostCreate(String username, String password, > String email) > BS> { > > BS> } > BS> Deployment decriptor entor > > BS> <ejb-name>User</ejb-name> > BS> > <local-home>com.n4i.ejb.test.UserLocalHome</local-home> > BS> <local>com.n4i.ejb.test.UserLocal</local> > BS> > <ejb-class>com.n4i.ejb.test.UserBean</ejb-class> > BS> > <persistence-type>Container</persistence-type> > BS> > <prim-key-class>java.lang.Integer</prim-key-class> > // I m using int(11) as the primary key if ur using > some unique string the specify java.lang.String > > BS> <reentrant>False</reentrant> > BS> <cmp-version>2.x</cmp-version> > BS> > <abstract-schema-name>User</abstract-schema-name> > BS> <cmp-field> > BS> <field-name>userID</field-name> > BS> </cmp-field> > BS> <cmp-field> > BS> <field-name>username</field-name> > BS> </cmp-field> > BS> <cmp-field> > BS> <field-name>password</field-name> > BS> </cmp-field> > BS> <cmp-field> > BS> <field-name>email</field-name> > BS> </cmp-field> > BS> <primkey-field>userID</primkey-field> > > > > BS> But u need to have getter and setter for this > unique sequence no primary key field ... as its > getter method will be used when u call getUserID on > local/Remote refernce of the entityBean . > BS> // One thing that is to noted here .is userID > field is managed by the DB not by EJB Container but > have to declare in the deployment descriptor as CMP > field > > BS> Eric this thing is working with mysql for mee .. > in oracle if ur using sequence as primary key its > value is integer .. and it will work tooo . > > BS> Rgds > > BS> Brijesh > > > BS> ----- Original Message ----- > BS> From: "Eric Tim" <[EMAIL PROTECTED]> > BS> To: <[EMAIL PROTECTED]> > BS> Sent: Tuesday, March 18, 2003 11:08 AM > BS> Subject: [JBoss-user] CMP - Primary Key > Strategies? > > > >> I'm working on a CMP EntityBean with JBoss3 on > >> Oracle8. > >> > >> My primary key must be a unique number. Oracle > has a > >> nice facility for handling sequences, which > doesn't > >> seam possible with this senerio because i'd need > to > >> write some jdbc code in the ejbCreate method to > get > >> the nextval. > >> > >> I'm aware that there are several J2EE > >> patterns/blueprints to solve this...most have > >> not-so-clean side effects that i'd like to > >> avoid...such as extra tables..etc. > >> > >> Is there anything that i can do with JBoss to > solve > >> this problem in a simple and clean manner? > >> > >> Someone told me that there is a cmp engine that i > can > >> buy that plugs into jboss that makes this easy. > Does > >> anyone know what product this is? Does anyone > have > >> experience with it? > >> > >> thanks, > >> -et > >> > >> > __________________________________________________ > >> Do you Yahoo!? > >> Yahoo! Platinum - Watch CBS' NCAA March Madness, > live on your desktop! > >> http://platinum.yahoo.com > >> > >> > >> > ------------------------------------------------------- > >> This SF.net email is sponsored by:Crypto > Challenge is now open! > >> Get cracking and register here for some mind > boggling fun and > >> the chance of winning an Apple iPod: > >> > http://ads.sourceforge.net/cgi-bin/redirect.pl?thaw0031en > >> _______________________________________________ > >> JBoss-user mailing list > >> [EMAIL PROTECTED] > >> > https://lists.sourceforge.net/lists/listinfo/jboss-user > >> > > > -- > costin > mailto:[EMAIL PROTECTED] > > > > ------------------------------------------------------- > This SF.net email is sponsored by: Does your code > think in ink? > You could win a Tablet PC. 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