Remove cycle between camel, spi and model
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Key: CAMEL-588
URL: https://issues.apache.org/activemq/browse/CAMEL-588
Project: Apache Camel
Issue Type: Improvement
Reporter: Christian Schneider
Fix For: 1.4.0
Attachments: post_camel_model_patch.png, pre_camel_model_patch.png
Currently there is a bad dependency cycle between camel, spi and model.
camel.CamelContext references model.RouteType. spi.RouteContext references
model.RouteType and model.FromType. Additionally spi.RouteContext and
spi.InterceptStrategy reference model.ProcessorType. These references are
especially bad ones as camel and spi are the most low level packages and these
references close the loop that makes camel one big tangle. I managed to remove
this tangle and so lower the excess(xs) measurement in structure 101 from 4300
to 2400. I added the dependency views to the issue. I hided the deprecated
CamelTemplate in the views to show that the cycle will be broken once we can
delete this.
The first thing I found out is that model is in my opinion not especially well
named. The model package is not the inner domain model of camel as the name
suggests but more the java dsl. So I think it could make sense to rename it at
some point into javadsl or dsl. This change would be too destructive so I did
not change this. But I think it is reasonable to define that camel and spi
should not be dependent on the dsl as the dsl is only needed while creating the
routes. So my goal was to cut these dependencies.
I first moved spi.RouteContext and spi.InterceptStrategy to model. With
RouteContext I am quite sure that this is a good thing as it is only needed in
the Java DSL and the builders. InterceptStrategy is of course part of an spi
but as it references model it can´t life in spi. As LifecycleStrategy
references RouteContext I split this interface in the part that does not
references RouteContext which I just left in spi and a new interface
ModelLifecycleStrategy which lives in model. This interface has the
onRouteContextCreate.
Then I reworked the communication between DefaultCamelContext and RouteBuilder.
I removed the routedefinitions from DefaultCamelContext and mode sure they are
not needed anywhere. So only the RouteBuilder knows about the definitions and
keeps them encapsulated. In the current code the intialization of the
RouteBuilder and the transfer of Routes and RouteDefinitions between
Routebuilder and DefaultCamelContext is very complicated and intransparent. The
getRouteList does the initialization as a side effect and additionally feeds
the route definitions into the CamelContext. This is extremly intransparent. I
replaced this with a simple and speaking method in Routes. btw I would vote to
rename Routes to RouteProvider. This would make the responsbility clearer.
List<Route> configureAndRetrieveRoutes(CamelContext context) throws Exception;
This method intializes the RouteBuilder, creates the definitions and routes and
simply returns the List of Routes. This is all communication between
DefaultCamelContext and RouteBuilder. The only little difference in behaviour
compared to before is that the Endpoint resolution happens already in this step
and not when the CamelContext is started.
All unit tests except one worked out of the box with this change. The one that
failed was RouteWithMistypeComponentNameTest. I this test the expected
exception happened now while adding the RouteBuilder to the context not when
starting the context. This was easily solved by extending the try to include
the addRoutes call. This is of course a minor change in contract but I believe
the architectural benefits are worth this little change.
I also had to do some little tweaks to make the GraphGeneratorSupport work
again. As CamelContext now does not know the route definitions this information
has to be taken from BuilderSupport. So made the CamelContext know all its
RouteBuilders as a list of Routes. In the Graph generation I then cast them to
BuilderSupport and extract the route defintions. So I was able to keep the
balance between encapsulation and enough knowledge to draw the graphs.
The last thing I did was to remove the createProcessor method from
RouteContext. I think this method was quite redundant. I was able to replace
all occurances of this with the much simpler call.
RouteType.createOutputProcessor. This removes another part of a cycle.
I set the version for this issue to 1.4.0 so it does not get lost but feel free
to move it to the version of camel where you want it solved. As this is a big
patch I would of course prefer it to be commited as soon as possible. If we
wait too long I probably have to redo the patch as there will be too many
changes in camel in the mean time.
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