Hi Joe, Question 1 :
you can't call the object constructor. Use the DataContext method instead because it will register the object too. Question 2 : It depends what you want ! DataContext dc = DataContext. getThreadDataContext(); > E1.getE2List().remove(e2); > dc.commitChanges(); This will remove the link between E1 and E2 but E2 will still exist. DataContext dc = DataContext. getThreadDataContext(); > dc.deleteObject(e2); > dc.commitChangesToParent(); > dc.commitChanges(); This will delete E2... but I think it will still be present in E1.getE2List() because the list can be in memory. I know it's not logical but I'm quite sure I allready encontered this case. I use Cayenne 2.0.4 so Cayenne 3.0 can differ in some points. Pierre Cordialement, Pierre Lavignotte Ingénieur Conception & Développement http://pierre.lavignotte.googlepages.com On Fri, Dec 26, 2008 at 6:32 PM, Joe Baldwin <jfbald...@earthlink.net>wrote: > I have a few questions about best practices. I have done some > experimenting, have read what I could find, and have some questions about > some elementary Cayenne usage concerning Add & Delete with a > Parent-ChildList design. (I have recently experienced some odd behavior > that may be due to a fundamental misunderstanding of DataContext rules.) > > Environment: I am using 3.0 M4 with MySQL and Tomcat JSP > DataContext: I am getting the context using: > DataContext.getThreadDataContext(); > Example Design: > E1 has a list of E2's > that is: > E2 is a child of E1 and is a many-to-one relationship. > The E1 relationship is called "E2List" and the reverse relationship > on E2 is called "E1". > > Questions: > 1. When creating and associating E2 children is it more proper to do the > following: > > DataContext dc = DataContext.getThreadDataContext(); > ** [get E1 via a DataContext query] > E2 e2 = new E2(); > e2.setE1(e1); // I **assume** this registers e2 with the Context & > adds e2 to e1's list > dc.commitChanges(); > > OR do you need to do as your example suggests: > > DataContext dc = DataContext.getThreadDataContext(); > E2 e2 = (E2) dc.newObject(E2.class); > e2.setE1(e1); > dc.commitChanges(); > > OR is there a better way? > > 2. Removal of a Child > Can you remove the child using: > DataContext dc = DataContext.getThreadDataContext(); > dc.deleteObject(e2); > dc.commitChangesToParent(); > dc.commitChanges(); > > or must you do it via the parent: > DataContext dc = DataContext.getThreadDataContext(); > E1.getE2List().remove(e2); > dc.commitChanges(); > > (Note: the second method seems to work better.) > > Thanks, > Joe > >
