Same ... Referring back to my original map files, the NullReferenceException is thrown by GetMember(). The 'obj' parameter is null and the memberName is 'Sessions' (so it's trying to get the Sessions collection on a null instance of the TrainingEvent objects.
> -----Original Message----- > From: Juan Pablo Araya [mailto:[EMAIL PROTECTED] > Sent: Monday, July 28, 2008 11:04 AM > To: [email protected] > Subject: Re: Problem mapping join on many tables to complex objects > > And with > > class A,B,C,D { > Nullable<int> ID { ... } > ... > } > > ? > > > > > 2008/7/28 Patrick Griffiths <[EMAIL PROTECTED]>: > > > > Thanks for reply. > > > > Null's seem to be the cause of the problem. Can iBatis > handle the case > > where the value of attributes in a join are mapped to > non-leaf complex > > objects? e.g > > > > If I have complex objects like this: > > > > class A > > { > > int ID {} > > IList<B> Bees { ... } > > } > > > > class B > > { > > int ID {} > > IList<C> Cees { ... } > > } > > > > class C > > { > > int ID {} > > IList<D> Dees { ... } > > } > > > > Then these result sets are OK: > > > > A_ID B_ID C_ID D_ID > > 1 1 1 1 > > 2 2 2 NULL > > > > But these will throw: > > > > A_ID B_ID C_ID D_ID > > 1 1 NULL NULL > > > > A_ID B_ID C_ID D_ID > > 1 NULL NULL NULL > > > > Patrick > > > > ________________________________ > > > > From: Jérome Avoustin [mailto:[EMAIL PROTECTED] > > Sent: Monday, July 28, 2008 2:08 AM > > To: [email protected] > > Subject: RE: Problem mapping join on many tables to complex > > objects > > > > > > > > Hi Patrick, > > > > > > > > Excuse me for being so "easy", but maybe it's > because of your left join ? > > > > It may return sometimes an "null Session" in your > data, so that iBatis can't map it to an object ! > > > > You may activate log4net and Debug level for > IBatisNet Logger to see your statements. > > > > > > > > Found on the iBatis.Net online documentation : > > > > > > > > "Lazy Loading vs. Joins (1:1) > > > > It's important to note that using a join is not > always better. If you are in a situation where it is rare to > access the related object (e.g. the category property of the > Product class) then it might actually be faster to avoid the > join and the unnecessary loading of all category properties. > This is especially true for database designs that involve > outer joins or nullable and/or non-indexed columns. In these > situations it might be better to use the sub-select solution > with lazy loading enabled. The general rule of thumb is: use > the join if you're more likely going to access the associated > properties than not. Otherwise, only use it if lazy loading > is not an option. > > > > If you're having trouble deciding which way to go, > don't worry. > > No matter which way you go, you can always change it > without impacting > > your application source code. Example 3.40 and 3.41 result > in exactly > > the same object graph and are loaded using the exact same > method call > > from the application. The only consideration is that if you were to > > enable caching, then the using the separate select (not the join) > > solution could result in a cached instance being returned. But more > > often than not, that won't cause a problem (your > application shouldn't > > be dependent on instance level equality i.e. "=="). » > > > > > > > > Hope this helps ! J > > > > > > > > Jérôme Avoustin > > > > > > > > > > > > -----Message d'origine----- > > De : Patrick Griffiths > [mailto:[EMAIL PROTECTED] > > Envoyé : samedi 26 juillet 2008 01:54 > > À : [email protected] > > Objet : Problem mapping join on many tables to > complex objects > > > > > > > > > > > > I'm trying to map from a single statement that joins > 4 tables > > into a > > > > deep complex object layout. The result maps look like this: > > > > > > > > <resultMap id="session-result" class="Session" > > groupBy="SessionID"> > > > > <result property="SessionID" column="Session_SessionID"/> > > > > <!-- Rest omitted for brevity --> > > > > </resultMap> > > > > > > > > <resultMap id="class-result" class="TrainingEvent" > > groupBy="ClassID"> > > > > <result property="ClassID" column="Class_ClassID"/> > > > > <result property="Sessions" > > > > resultMapping="SessionSqlMap.session-result" /> > > > > <!-- Rest omitted for brevity --> > > > > </resultMap> > > > > > > > > <resultMap id="course-result" class="TrainingActivity" > > > > groupBy="CourseID"> > > > > <result property="CourseID" column="Course_CourseID"/> > > > > <result property="TrainingEvents" > > > > resultMapping="TrainingEventSqlMap.class-result"/> > > > > <!-- Rest omitted for brevity --> > > > > </resultMap> > > > > > > > > <resultMap id="company-result" class="Company" > > groupBy="CompanyID"> > > > > <result property="CompanyID" column="Company_CompanyID"/> > > > > <result property="TrainingActivities" > > > > resultMapping="CourseSqlMap.course-result"/> > > > > <!-- Rest omitted for brevity --> > > > > </resultMap> > > > > > > > > and the SQL is: > > > > > > > > SELECT /* fields omitted for brevity */ > > > > FROM Company c INNER JOIN > > > > Course cr ON c.CompanyID = cr.CompanyID LEFT JOIN > > > > Class cl ON cr.CourseID = cl.CourseID LEFT JOIN > > > > Session s ON cl.SessionID = cl.SessionID > > > > > > > > iBatis has no problem mapping the Company, Course and Class > > fields into > > > > the complex object structure, but it throws a > > NullReferenceException > > > > when it tries to map the fields from the Session > table - even > > when I use > > > > the very simple abbreviated result maps above. > > > > > > > > Any help identifying where I'm going wrong would be > much appreciated. > > > > > > > > Thanks. > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > > >
