Hello everybody,
I just wanted to share what we discovered while updating to Camel from 2.25
to 3.4. There was no blocker but some unexpected things that weren't in the
migration guide. Maybe we're doing it wrong, please tell me if there's a
better way.
Let's start with a bit of context. We're using multiple Camel contexts on
an OSGi platform and their configurations are stored in a database using
the XML format. Yes, OSGi and XML, they're no longer the cool kids on the
block but it's working really well :)
First, it's not possible to manually
call addRouteDefinitions(Collection<RouteDefinition>) on a brand
new OsgiDefaultCamelContext. The init() method called at the end of the
constructor since CAMEL-14399 initializes the context without routes,
routes added later seemed ignored. We managed to make it work by overriding
the init() method with a no-op method and calling init() after configuring
routes. I have to admit that I don't know if it's an issue or not, I don't
know the nominal case or the expected behavior.
Reifiers truly are a great improvement compared to Camel 2.x, they nicely
split execution model and runtime. We have custom processors and
expressions and we, unfortunately, discovered reifiers the hard way as
they're not documented in the migration guide. I have no clue on the proper
way to document them as they're quite technical and not everybody has
custom processors and expressions.
It was easy to add custom processor reifiers but harder to add expression
ones, we had to use a bit of reflection to access the map holding them,
there's no public accessor (should it have one?)
Speaking of expressions, it looks like it's not possible to have
expressions that aren't derived from an ExpressionDefinition, that aren't
configured as a String. We have many of them, they're quite useful
(especially in XML with different namespace), here is an exemple:
<u:date-parse pattern="dd MMMM yyyy" tz="UTC" locale="FR_FR">
<simple>${body[date]}</simple>
</u:date-parse>
Lastly, I wanted to thank you all for your hard work. The new documentation
and migration guide are truly awesome and helped us a lot. You also did an
amazing job splitting the core into separate projects, it makes it much
cleaner.
That's all for me, have a nice day,
Antoine
