Re: [Xdoclet-user] real m-n relations

[Joseph Parks]

I know that xdoclet (CVS snapshot from ~a week ago) supports real m:n relations (as defined in mastering ejb 2nd ed.) with Weblogic.  Bi-directional is easy: put the @ejb.relation tag with the same name in both beans, each associated with an abstract getter that returns a java.util.Collection:   // StudentBean.java /**    *    @ejb.interface-method    view-type="local"    *    @ejb.relation    name="students-courses"    *                             role-name="student-has-many-courses"    *    @weblogic:relation    join-table-name="student_xref_course"    *    @weblogic:column-map   foreign-key-column="student_id"    *                                             key-column="student_id"    */ public abstract java.util.Collection getCourses();   /**    *    @ejb.interface-method    view-type="local"    */ public abstract void setCourses( java.util.Collection courses );     // CourseBean.java /**    *    @ejb.interface-method    view-type="local"    *    @ejb.relation    name="students-courses"    *                             role-name="course-has-many-students"    *    @weblogic:relation    join-table-name="student_xref_course"    *    @weblogic:column-map   foreign-key-column="course_id"    *                                             key-column="course_id"    */ public abstract java.util.Collection getStudents();   /**    *    @ejb.interface-method    view-type="local"    */ public abstract void setStudents( java.util.Collection students );     I think the term "real m:n relationships", though, is a misnomer.  This just doesn't describe reality.  For example, the student's grade for a given course cannot be described in this object model.  In reality, "grade" would be a field in the above "student_xref_course" table.  It is better mapped using a "fake" m:n relationship.  In other words, two 1:m relationships--Student:Enrollments, Course:Enrollments. In the book, Roman says that he prefers the fake relationships, but (I think) for the wrong reason.  It's not about extensibility or control.   HTH, Joe >>> "Ingo Bruell" <[EMAIL PROTECTED]> 05/07/02 10:51AM >>> Hi Aslak, > Hi. I don't understand what you mean by "real relations" > and "enrollment table". Are you talking about unidirectional m:n > relations? Join tables? I have used the termini from the book MasteringEJB2. That says that m:n relations that uses a enrolement table are fake m:n relations and m:n relations that uses Collections or something else to holde the relation information are real m:n realtions. > Anyway, XDoclet should(*) support relations with any combination of > directionality and cardinality, at least on the ejb-jar.xml level. See > documentation for @ejb:relation. i am using xdoclet drom cvs (one week old), jboss3.0.0RC2 and jdk1.4. CU Ingo Br�ll _______________________________________________________________ Have big pipes? SourceForge.net is looking for download mirrors. We supply the hardware. You get the recognition. Email Us: [EMAIL PROTECTED] _______________________________________________ Xdoclet-user mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/xdoclet-user