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From Andrus Adamchik <and...@objectstyle.org>
Subject Re: IOC container
Date Mon, 16 Nov 2009 14:43:55 GMT
Do you mean multiple DataDomains?

I don't have all the details yet, but the container API will be  
extended as needed to fit our needs. For now I am thinking that all  
cases where we need to access objects by name, will be delegated to  
Configuration and other objects outside container. The container may  
store maps of all names, and Configuration will be a frontend to read  
from those maps.

But if we find that extending the container is beneficial, we can do  
that too. E.g. I am planning something similar to Tapestry  
configurations for the users to register/override ExtendedTypes, so  
that the users don't have to redefine all types if they need to add  
just one extra object.

Also to ensure we are on the same page, I am not planning app-facing  
injection, just internal injection of Cayenne classes between  
themselves. I.e. we won't inject anything in an app class that is  
calling an ObjectContext (unless it is an override for the standard  
service).

And finally, unrelated, but since DataDomains were mentioned... I've  
been thinking to do away with multiple DataDomains. They are really  
independent stacks, so why bother keeping them together in one  
project. The users can start multiple Cayenne stacks instead.

Andrus


On Nov 16, 2009, at 4:28 PM, Michael Gentry wrote:
> How are you envisioning injecting an ObjectContext for different  
> DataNodes, etc?
>
> Thanks,
>
> mrg
>
>
> On Sun, Nov 15, 2009 at 4:57 PM, Andrus Adamchik <andrus@objectstyle.org 
> > wrote:
>> Just for kicks wrote a simple DI container for Cayenne. I checked  
>> it in
>> partially to sanbdox folder until the ASF SVN repo went down
>> (http://monitoring.apache.org/), so I'll commit the rest on Monday,  
>> or
>> whenever SVN becomes available.
>>
>> This no-frills DI container took me only a couple of hours to write  
>> (it
>> borrows some Guice API, but implementation is all mine). It supports
>>
>> * annotation-based field dependency injection
>> * binding interfaces to implementation classes via fluent API
>> * binding interfaces to "provider" (same as "factory") classes
>> * merging multiple DI "modules".
>>
>> The whole thing is only 14K after compilation (so it beats all full  
>> featured
>> DI containers in size). Of course that's because it doesn't have  
>> all the
>> fancy stuff (of which we'll add at least a few more things) such as
>> constructor injection, dependency cycle resolving, dynamic interface
>> proxies, bound object lifecycle, integration with Spring, etc.  
>> Since we are
>> not planning a general purpose container, we might survive without  
>> most of
>> those.
>>
>> Here is how the current Configuration class might look like when it  
>> is based
>> on DI:
>>
>> public class Configuration {
>>
>>        private Injector injector;
>>
>>        public Configuration() {
>>                this(new CayenneModule());
>>        }
>>
>>        public Configuration(Module... modules) {
>>                this.injector = DIBootstrap.createInjector(modules);
>>        }
>>
>>        public DataChannel getDataChannel() {
>>                return injector.getInstance(DataChannel.class);
>>        }
>>
>>        public ObjectContext getNewContext() {
>>                return injector.getInstance(ObjectContext.class);
>>        }
>>
>>        // we may create getters for other "services" if we need to
>> }
>>
>> And the actual configuration class (aka "module") used above:
>>
>> public class CayenneModule implements Module {
>>
>>        public void configure(Binder binder) {
>>                 
>> binder.bind(EventManager.class).to(EventManagerImpl.class);
>>                binder.bind(DataChannel.class).to(DataDomain.class);
>>
>>  binder.bind(QueryCache.class).toProvider(LRUCacheFactory.class);
>>                 
>> binder.bind(QueryLogger.class).toProvider(FancyLogger.class);
>>                // an so on...
>>        }
>> }
>>
>> "CayenneModule" is what users can override (e.g. simply subclass),  
>> providing
>> alternative implementations for some services.
>>
>> The next step in this prototype would be an attempt to define the  
>> current
>> Cayenne stack in terms of DI.
>>
>> Andrus
>>
>> On Oct 27, 2009, at 11:01 PM, Kevin Menard wrote:
>>
>>> On Sun, Oct 25, 2009 at 5:05 PM, Andrus Adamchik <andrus@objectstyle.org 
>>> >
>>> wrote:
>>>
>>>> And I just discovered that both Spring (3.0RC1) and Juice (trunk)  
>>>> support
>>>> the annotations from this JSR. So it could make sense for us to  
>>>> use these
>>>> annotations internally as well. Couldn't dig any info on the  
>>>> Tapestry IoC
>>>> support for this JSR, but they are on the JSR "support group", so  
>>>> at
>>>> least
>>>> they are watching it.
>>>
>>> Thiago, the Tapestry member on the support group, just learned  
>>> that it
>>> had been approved.  Howard didn't even know the JSR existed.   
>>> There's
>>> no discussion on adding in the annotation support to Tapestry IoC  
>>> and
>>> I suspect it will happen, but Tapestry is behind the ball on that  
>>> one.
>>>
>>> --
>>> Kevin
>>>
>>
>>
>


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