Hi > > I am thick headed... please forgive me. But one last > question. (see question > below). > > > -----Original Message----- > > From: Mahler Thomas [mailto:[EMAIL PROTECTED]] > > Sent: Monday, September 02, 2002 8:24 AM > > To: 'OJB Users List' > > Subject: AW: SELECT statements and OJB > > > > > > Hi again, > > > > > > 1. OJB does *not* perform "select * from", for queries! > > > > If you look up objects of class x OJB will read the > > > class-descriptor for > > > > class x and determine all necessary columns to materialize > > > an x instance. > > > > The performed select contains all those columns. > > > > > > > > If you want to limit the number of columns you can modify the > > > > class-descriptor for class X do get a reduced number of columns. > > > > > > > > > > So, if i needed a full person to be materialized in one place > > > and only the > > > id, firstname and lastname elsewhere then I would have to > > > write a couple of > > > classes and their associated class-descriptor. For example my > > > PersonName and > > > Person would be two different object classes that are > > > populated from the > > > same table (PEOPLE). > > > > NO! You only need one persistent class Person. > > You can modify the existing class-descriptor for class > Person at runtime. > > that is for one query you remove all columns you don not > want to see from > > the classdescriptor. > > After finishing the query you restore the class-descriptor > to its original > > Form so that all other things work normally. > > I guess what i am saying here is i need both representations > in the same > web-app. For example, within the same web application, i have > a place where > you can 1) select a person to edit and 2) a place to edit a person's > information. > > 1) This requires that i retrieve only the ID, FIRSTNAME AND > LASTNAME of all > the records in the PEOPLE database. I then display the names > on an html > page. The user then selects which person they want to edit > and we are off to > edit that person's info. In this case i only want to populate the id, > firstName and lastName variables in the Person object/class > and store it > into a collection to be traversed on the html page and > displayed. My problem > arises in reusing my Person class because i already have it > in use with step > 2's class descriptor. If i undestand you correctly i will > have to create a > BasicPerson class that only contains the id, firstName and lastName > variables and a class descriptor that maps to the BasicPerson > class.
As stated in my original mail: NO! You only need one persistent class Person!!! You can modify the existing class-descriptor for class Person at runtime. that is for one query you remove all columns you don not want to see from the classdescriptor. After finishing the query you restore the class-descriptor to its original Form so that all other things work normally. > Please > read on to step 2) > > 2) This requires that i retrieve all of the fields for a > particular person > from the database table PEOPLE and populate a Person object > to pass to the > form that will be populated by that information for editing. > Therefore, i > would set up my class descriptor to get all the column values from the > database and poulate the Person class which has the accordingly mapped > setters and getters. At the same time in the same app i have > need for just > the retrieval of the PEOPLE table's ID,FIRSTNAME and > LASTNAME. In this case > i am listing all of the names of the people so that a name > can be selected > to edit a person's info. I don't want to get all the other > fields in the > records because it would be pointless to populate it with all > the colums > from the PEOPLE table cuz i don't need them. > > Conclusion: > > Now, does this mean that i would have to have two different > classes mapped > with two different class-descriptors to handle each of these > situations. NO !!! (Could somebody else please tro to explain this? I have no idea why you still believe that you will need two classes?) > > If yes, then are there any planned enhancements to allow for > more efficient > reuse of classes? > > I am afraid that you might take my questioning as an insult. Not as an insult. I simply do not get what you do not understand in my reply? cheers, Thomas > I don't mean it > that way. I just want a clear and accurate picture of what i > am able to and > not able to do. Also, you documentation and work on this is > execellent. I > know that projects grow faster than their docs and that's > just reality. > Great Work! I never meant to say otherwise. > > > > > -- > To unsubscribe, e-mail: > <mailto:[EMAIL PROTECTED]> > For additional commands, e-mail: > <mailto:[EMAIL PROTECTED]> > -- To unsubscribe, e-mail: <mailto:[EMAIL PROTECTED]> For additional commands, e-mail: <mailto:[EMAIL PROTECTED]>
