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From Andrus Adamchik <and...@objectstyle.org>
Subject Re: Creating a new ServerRuntime from an existing ServerRuntime
Date Fri, 27 Sep 2013 16:49:43 GMT
> So it looks like I can reuse modules to create my own runtime.

Yes.

> However, the current 3.1 API isn't very friendly toward this approach.


Yes - see my other email. A common pattern is to have some kind of external factory that defines
the modules. 

Also I don't perceive 'copy' method as very useful. The point of a second runtime is that
it is somehow different from the first, and modules is what makes it different. I think you
are doing it in a pre-3.1-DI-way - creating a runtime first, then customizing it. I would
usually place customization code inside the modules, which are kind of deferred "closures".

Andrus


On Sep 27, 2013, at 7:39 PM, Mike Kienenberger <mkienenb@gmail.com> wrote:

> So it looks like I can reuse modules to create my own runtime.
> However, the current 3.1 API isn't very friendly toward this approach.
> I had to clone the ServerRuntime class so that I could create my own
> version so I could call CayenneRuntime(Module... modules) in my
> constructor.
> 
> Having a cloned ServerRuntime on which to make customizations seems
> like a reasonable use case that we should support.   Can we add such a
> method to ServerRuntime?   I think that's a better choice than making
> it easier to create a ServerRuntime subclass.
> 
> private ServerRuntime(Module... modules) {
>    super(modules);
> }
> 
> public ServerRuntime copy() {
>        return ServerRuntime(serverRuntime.getModules());
> }
> 
> It might be reasonable to make the private constructor public so that
> someone can create ServerRuntimes where they are not required to pass
> configurationLocation data but can provide their own alternative to
> ServerModule.  This would have also worked in my case, removing the
> need to have a copy() method.   However, I think the copy() method
> provides assurance to the developer that this approach is viable.
> 
> 
> Here's what my application code ended up looking like (using my cloned
> class), and I think it's a good approach (except for the cloned class)
> for these cases:
> 
>        PaymentMethod paymentMethod = paymentHistory.getPaymentMethod();
>        if (null == paymentMethod) {
>            ServerRuntime currentRuntime = ServiceLocator.getCayenneRuntime();
> 
>            // Payment method was invalidated at this point -- create
> a runtime that can read invalidated payment methods
> 
>            CopiedServerRuntime copiedRuntime = new
> CopiedServerRuntime(currentRuntime);
>            DataDomain dataDomain = copiedRuntime.getDataDomain();
>            dataDomain.setSharedCacheEnabled(false);
> 
>            EntityResolver entityResolver = dataDomain.getEntityResolver();
>            ObjEntity paymentMethodObjEntity =
> entityResolver.getObjEntity(PaymentMethod.class.getSimpleName());
>            paymentMethodObjEntity.setDeclaredQualifier(null);
> 
>            ObjectContext unrestrictedObjectContext =
> copiedRuntime.getContext();
>            PaymentHistory unrestrictedPaymentHistory =
> unrestrictedObjectContext.localObject(paymentHistory);
>            paymentMethod = unrestrictedPaymentHistory.getPaymentMethod();
>        }
> 
> 
> On Fri, Sep 27, 2013 at 11:46 AM, Mike Kienenberger <mkienenb@gmail.com> wrote:
>> The idea of creating a new ServerRuntime is good, but the
>> implementation leaves  me with a few questions.    My ServerRuntime is
>> created in the context of the web app.
>> 
>> Is it reasonable to try to create it using the information in the
>> existing ServerRuntime?   Can I pull the injector and modules out of
>> the existing Runtime and reuse them to create a new runtime, or do I
>> need to create copies of the existing modules and injector?   My guess
>> is that each runtime needs unique injector and modules objects, but I
>> want to minimize the work I need to do.
>> 
>> It looks like I have to pull my configurationLocation out of the
>> ServerModule, which doesn't really provide it.
>> 
>> I'm not seeing an easy way to create a new ServerRuntime from scratch
>> without having access to data which was only available back when the
>> web application started up, short of storing that information
>> somewhere globally and reusing it.
>> 
>> On Tue, Sep 24, 2013 at 2:04 PM, Andrus Adamchik <andrus@objectstyle.org> wrote:
>>>> The "special DataContext" case where the qualifier should be ignored can
probably be handled by starting a separate ServerRuntime, where you can strip off the qualifiers.
For whatever overhead it creates (ideally not much), this has an advantage of cleanly separating
"spaces" with different ORM rules.
>>> 
>>> Elaborating on this a bit… The old Configuration allowed multiple DataDomains,
each of those requiring its own DataMap(s) saved in the project upfront. Good idea, but hard
to use in practice.
>>> 
>>> ServerRuntime (with single DD each) is more user-friendly. By starting multiple
independent runtimes you to easily reuse a single mapping project, tweaking each in-memory
copy local to each Runtime (as well as tweaking other parameters like cache). 2 Runtimes can
reuse a single DataSource (JNDI, or otherwise), etc.
>>> 
>>> Andrus
>>> 
> 


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