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[nhibernate-issues] [JIRA] Commented: (NH-1344) QueryTranslator: Invalid Cast to object array when using IResultTransformer
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From: NHibernate J. <nh...@gm...> - 2008-06-18 14:36:42
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[ http://jira.nhibernate.org/browse/NH-1344?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16429#action_16429 ]
Stefan Simroth commented on NH-1344:
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Sorry, but after spending some time to create a simple test case, the problem doesn't appear :/
The obvious differences between my simple test case and our real world app are the much bigger domain model with a custom database schema and various child (sub) elements in Iesi Sets, as well as quite some more calls at runtime to the various ISession methods (like query, save, etc.)...
So, in short, I'm afraid I cannot put more time into this, as with the patch, it works for me.
Tell me, if you are interested in the simple scenario test case, where the problem does not occur. Maybe someone wants to further develop it.
Definitely, I (or some colleague of mine) will come back, if the problem causes serious trouble.
> QueryTranslator: Invalid Cast to object array when using IResultTransformer
> ---------------------------------------------------------------------------
>
> Key: NH-1344
> URL: http://jira.nhibernate.org/browse/NH-1344
> Project: NHibernate
> Issue Type: Patch
> Components: Core
> Affects Versions: 1.2.0.GA, 1.2.1, 2.0.0.Alpha1, 2.0.0.Alpha2
> Reporter: Stefan Simroth
> Priority: Minor
> Attachments: QueryTranslatorInvalidCastToObjectArray20trunk.patch
>
>
> there seems to be an issue with a hard cast in the QueryTranslator
> class, line 1452 (trunk) - resp. line 1288 (1.2.1) ...
> The hard cast in method GetResultList to an object[] fails in the case
> of my company's product, when using an IResultTransformer.
> I chose to use an IResultTransformer implementation for Criteria's and
> Query's to be able to set a required property. It seems an appropriate
> way to me and my tests (and the running app) ensure that it works.
> However, I had to patch the QueryTranslator at the locations mentioned
> above, because it threw an invalid cast exception (stacktrace below) -
> because the IList of my objects could not be casted to an object[].
> Debugging it, showed me that the "results" list contained my domain
> objects, but it could not be casted to an object[]. It was a collection
> of my domain types and my domain types are no object[]. Now, some time
> passed by since then, and our product works fine with the patch, so
> unfortunately I forgot the exact reason, but I'd guess, I used the
> generic Query signature and so the results list was a generic list that
> cannot be casted to object[]. But also ArrayList or Hashtable cannot be
> casted to object[]...
> A little experiment, gave me the compiler error:
> Cannot convert type
> 'System.Collections.Generic.List<ConsoleApplication1.Project>' to 'object[]'
> class Program
> {
> static void Main(string[] args)
> {
> List<Project> projects = new List<Project>();
> object[] objs = (object[]) projects;
> }
> class Project { }
> }
> => same thing doesn't work with ArrayList or Hashtable ...
> ----
> The code snippet from QueryTranslator in question:
> for (int i = 0; i < results.Count; i++)
> {
> object[] row = (object[]) results[i];
> results[i] = holderInstantiator.Instantiate(row);
> }
> ----
> Patch - with a "safe" cast:
> object[] row = results[i] as object[];
> if (row != null)
> {
> results[i] = holderInstantiator.Instantiate(row);
> }
> The included patch is for the NHibernate 2.0 trunk.
> The same problem exists in earlier versions, namely 1.2.
> I might be totally missing the root of the problem, but please excuse
> this, as I am not familiar with the NHibernate internals, but tried to
> apply a patch at the right place to enable the very useful feature of
> the IResultTransformer to our case - and maybe to others in future.
> Here is the stacktrace: (version 1.2.1)
> at NHibernate.Hql.Classic.QueryTranslator.GetResultList(IList
> results, IResultTransformer resultTransformer) in
> d:\dev\yap\nhibernate\trunk\src\NHibernate\Hql\Classic\QueryTranslator.cs:line
> 1291
> at NHibernate.Loader.Loader.ListIgnoreQueryCache(ISessionImplementor
> session, QueryParameters queryParameters) in
> d:\dev\yap\nhibernate\trunk\src\NHibernate\Loader\Loader.cs:line 1744
> at NHibernate.Loader.Loader.List(ISessionImplementor session,
> QueryParameters queryParameters, ISet querySpaces, IType[] resultTypes)
> in d:\dev\yap\nhibernate\trunk\src\NHibernate\Loader\Loader.cs:line 1738
> at NHibernate.Hql.Classic.QueryTranslator.List(ISessionImplementor
> session, QueryParameters queryParameters) in
> d:\dev\yap\nhibernate\trunk\src\NHibernate\Hql\Classic\QueryTranslator.cs:line
> 1124
> at NHibernate.Impl.SessionImpl.Find(String query, QueryParameters
> parameters, IList results) in
> d:\dev\yap\nhibernate\trunk\src\NHibernate\Impl\SessionImpl.cs:line 1763
> ----
> My IResultTransformer implementation:
> #region IResultTransformer Members
> public object TransformTuple(object[] tuple, string[] aliases)
> {
> object o = CriteriaUtil.RootEntity.TransformTuple(tuple, aliases);
> TrySetDomainModelStore(o);
> return o;
> }
> public IList TransformList(IList collection)
> {
> for (int i = 0; i < collection.Count; i++)
> {
> TrySetDomainModelStore(collection[i]);
> }
> return collection;
> }
> #endregion
> TranformTuple is called rarely. TransformList is called after the
> HolderInstantiator call.
> I never create a new MyEntity[] { my, domain, entities}, nor a new
> object[] { my, domain, entities} ...
> ------
> Felix Gartsman:
> Isn't this similar to Hibernate issues:
> http://opensource.atlassian.com/projects/hibernate/browse/HHH-2463
> http://opensource.atlassian.com/projects/hibernate/browse/HHH-2525
> They are also present in NH, and they prevent caching queries with
> IResultTransformer - the caching thinks it gets a tuple, but it's actually
> the transformed object.
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