@Oskar
That require method is pretty much what I was looking for. At least that
gives me 80% of what I was looking for.
No idea why I didn't think of that either seems like an easy win for all
those null checks.
Thanks, Mark
On Wednesday, August 3, 2016 at 11:17:58 PM UTC+1, Oskar Berggren wrote:
>
>
>
> If you have an interceptor that runs before your handler, wouldn't that
> validation take place inside the same session that would later be used for
> the handler? So if you do the validation by calling ISession.Get(), it
> would be in the first level cache and no need to worry about the cache part.
>
> But is it important to have it run _before_ the handler? The attribute in
> your example is in the command definition, so it would not be immediately
> obvious in the handler code that it's ok to skip the validation there,
> which could be somewhat confusing I guess.
>
> If it's ok to let the handler do the validation, how about calling
> something like this instead of Get:
>
> var customerType = _session.Require<CustomerType>(cmd.customerTypeId)
>
>
> public static T Require<T>(this ISession session, object id)
> {
> T entity = session.Get(id);
> if (entity == null)
> throw something;
> return entity;
> }
>
> Come to think about it, I wonder why I'm not already doing this in my
> applications. I'm gonna have to look into that.
>
> Of course, session.Load() already does something similar except the
> validation won't happen until you actually try to use the entity.
>
> Perhaps we should add the Require() method to NHibernate itself.
>
> /Oskar
>
>
>
> 2016-08-02 15:13 GMT+01:00 Mark Perry <[email protected] <javascript:>>:
>
>> Hi
>>
>> I have been working with NH for some years now and have seen a pattern
>> emerging in my code that I'd like to see if there is a better way of
>> handling.
>>
>> Most of my "service/handler" classes do stuff like this:
>>
>> public class CreateCustomerCommandHandler: IHandleCommand<
>> CreateCustomerCommand>{
>>
>> private ISession _session;
>>
>> public CreateCustomerCommandHandler(ISession session){
>> _session = session;
>> }
>>
>> public void Handle(CreateCustomerCommand cmd){
>> var customerType = _session.Get<CustomerType>(cmd.customerTypeId);
>> var customerSex = _session.Get<CustomerSex>(cmd.customerSexId);
>> var client = _session.Get<Client>(cmd.ClientId);
>> //More entity loads here
>>
>> if(customerType == null)
>> throw new NotFoundException($"CustomerType not found with id of
>> {cmd.customerTypeId}");
>>
>> //More checks for null here
>> }
>>
>> }
>>
>> What I would like to do is to check an Entity Id Cache of some sort
>> before the code reaches my "Handler" classes. That way I know whether the
>> entity is in the DB before I run my handler code.
>>
>> Think of it like Validation for entities existing.
>>
>> I could then implement a CommandInterceptor which does the Id validation
>> before passing off to the CommandHandler.
>>
>> public class CreateCustomerCommand: ICommand{
>> [EntityCache(typeof(CustomerType))]
>> public customerTypeId {get;set;}
>> //etc...
>> }
>>
>>
>>
>> I know the second level cache exists and I can cache entities in that
>> which does kinda give me what I want (with the benefit that when I do the
>> load in the Handler no need to go to the DB).
>>
>> I just wondered if there was another pattern or feature of NH I was
>> missing in order to achieve what I am trying to do?
>>
>> Any thoughts would be greatly appreciated.
>>
>> Thanks, Mark
>>
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