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Date: Mon, 28 Dec 2009 17:51:05 -0800
Message-ID: <55f2e4a80912281751w563caf4ak39f0da98894a12d5@mail.gmail.com>
Subject: Re: Startup invocation of a route
From: Stephen Gargan <steve.gargan@gmail.com>
To: users@camel.apache.org
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Hi,

So I like to think of "direct" endpoints as internal connectors for
for linking routes. They are a great way of decoupling the business
and workflow logic in your routes from the transport related logic.

Say for instance your service that Quartz executes is defined in a
bean 'myservice'. You might have a route that looks very like

from("quartz://services/myService?trigger.repeatInterval=10000").to("bean:myService");

you could decouple the bean invocation from the quartz trigger as follows.

from("quartz://services/myService?trigger.repeatInterval=10000").to("direct:my-service-in");
from("direct:my-service-in").to("bean:myservice");

the choice of "direct:my-service-in" as the name is entirely
arbitrary, as arbitrary as "direct:start" in lots of the tests. But as
it appears in the 'to' of one route and the 'from' in another the two
routes are now linked with this virtual channel and when the quartz
endpoint fires it will drive the direct endpoint which will
synchronously drive the bean my service.

Why would you want to do this? well think about testing your routes.
You have your business logic route which can now be very easily driven
and tested by sending exchanges to this "direct:my-service-in" with no
need to setup much transport logic. This makes for cheaper cleaner
route tests as you can test the transport and logic independently.

Getting back to your scenario, you want to be able to invoke the
service route on startup. Now that you have decoupled the routes you
can simply add another route that also sends an exchange 'to' the
"direct:my-service-in" uri when your app starts.

If you're using spring you get this very cheaply as the
SpringCamelContext will kick off a spring event when the context
starts. You could create a route to consume this spring event and
forward it to your service via its direct uri

from("spring-event:default").to("direct:my-service-in"); // note you
may need to filter the kinds of spring events you want to trigger the
service.

or you could just use a producer template to fire it in your main
class after everything is set up.

template.sendBody("direct:my-service-in"", "Inital invocation or whatever");

Main take away is that direct endpoints are your friend and great for
decoupling.

Hope this helps, shout back if not.

ste


On Mon, Dec 28, 2009 at 3:29 PM, huntc <huntc@mac.com> wrote:
>
> One thing that has always eluded me is how to specify that something be done
> immediately upon the CamelContext having started up.
>
> For example, I have a Quartz based service that executes every hour at 10
> minutes past the hour. However when the CamelContext starts up I'd like this
> service to be invoked immediately and then go into its scheduling behaviour.
> This is so that other consumers of the services I provide can get their data
> immediately without having to wait up to an hour given service startup.
>
> Firstly it'd be great if there was an option on the Quartz component to
> always fire off an initial event. However in general terms it'd be great to
> have the ability to specify that a route is invoked upon the CamelContext
> having been established (with all of its routes configured within the
> current RouterBuilder). Perhaps RouteBuilder needs a new overide-able method
> that is invoked in this situation.
>
> Incidentally I see many references to from("direct:start") throughout the
> doco and examples, but no idea of how this route is invoked.
>
> Thanks for any help in unwinding my confusion.
> --
> View this message in context: http://old.nabble.com/Startup-invocation-of-a-route-tp26949232p26949232.html
> Sent from the Camel - Users mailing list archive at Nabble.com.
>