----- Original Message ----- From: "Luis A" <[EMAIL PROTECTED]> To: "Jason Carreira" <[EMAIL PROTECTED]> Sent: Tuesday, January 15, 2002 6:50 AM Subject: Re: Re: As a Person Looking into EJB...
> Hi there, I am sorry, but this does not seem to be the answers to the > original "As a person" thread in which I got very interested. Has there been > something offline? I would like to hear comments about the first questions. > > Kindly, > > Luis. > > > ----- Original Message ----- > From: "Jason Carreira" <[EMAIL PROTECTED]> > To: <[EMAIL PROTECTED]> > Sent: Tuesday, January 15, 2002 12:17 AM > Subject: Re: As a Person Looking into EJB... > > > > Hi Atong, > > > > > -----Original Message----- > > > From: A mailing list for Enterprise JavaBeans development > > > [mailto:[EMAIL PROTECTED]]On Behalf Of Atong Appa > > > Sent: Monday, January 14, 2002 7:17 PM > > > > > > I have a few issues with EJB's persistence. In fact, the > > > first one of these > > > problems is not even unique to EJB, but OO paradigm in > > > general. Many of > > > objects has many columns of data (over 100 columns). When an > > > application is > > > running, the user typically works only with only a handful of > > > these columns > > > (human beings are not equipped to deal with 100's of pieces > > > of info all at > > > once). > > > > > > So, different applications ('modules' to be exact) work on > > > different subsets > > > of this large number of columns. Yet, the business logic must be > > > centralized and managed in the context of one object class (like you > > > mentioned). > > > > > > The problem is that OO paradigm wants the entire object to be > > > realized in > > > memory before anything happens. This causes memory usage problems, > > > scalability problems, and performance problems. Previously, > > > we've attempted > > > to implement 'partially initialized' object, but, like you > > > said, this ended > > > up strewing bits of SQL in many places--maintenance problems. > > > > > > For this kind of problems, EJB CMP is inappropriate. With BMP, we are > > > likely to end up with SQL spread out. Is there something in > > > EJB to help out > > > with this kind of problem? > > > > > > > Some vendors have optimizations for this type of thing. For instance, > > Weblogic has the concept of field groups. Here's the documentation on them > > from the XDoclet docs on the @weblogic:field-group tag: > > > > > > > > A field-group represents a subset of the cmp and cmr-fields of a bean. > > Related fields in a bean can be put into groups which are faulted > > into memory together as a unit. A group can be associated with a > > query or relationship, so that when a bean is loaded as the > > result of executing a query or following a relationship, only the > > fields mentioned in the group are loaded. > > > > A special group named 'default' is used for queriess and relationships > > that have no group specified. By default, the 'default' group contains > > all of a bean's cmp-fields and any cmr-fields that add a foreign key to > the > > persistent state of the bean. > > > > A field may belong to multiple groups. In this case, the getXXX() method > > for the field will fault in the first group (lexically speaking) that > > contains the field. > > > > > > > > In this way you can have partially initialized objects that only pull in > > the pieces it thinks it needs... While this is a vendor-specific > > optimization, it is mapped into the weblogic deployment descriptor, so it > > does not make your code any less portable (although you won't have these > > optimizations on another product, unless they have something similar). > > > > HTH, > > > > Jason Carreira > > > > > =========================================================================== > > To unsubscribe, send email to [EMAIL PROTECTED] and include in the > body > > of the message "signoff EJB-INTEREST". For general help, send email to > > [EMAIL PROTECTED] and include in the body of the message "help". > > > > > =========================================================================== To unsubscribe, send email to [EMAIL PROTECTED] and include in the body of the message "signoff EJB-INTEREST". For general help, send email to [EMAIL PROTECTED] and include in the body of the message "help".
