Hi Zoran,
Just in case, Properties component already provide the feature of
specifying a default value with {{speedUp:other}} syntax:
https://camel.apache.org/components/3.7.x/properties-component.html#_syntax
So what Claus proposes here is a feature that optionally can assign some
value but otherwise leaves it unassigned at all.
I see Claus' point that the syntax {{optional:speedUp}} is really confusing
as the properties component would then see it as the placeholder "optional"
with default value "speedUp".
Personally, I second Babak's syntax of {{speedUp?}} as it aligns with JS
syntax and REST producer optional parameters Zoran introduced.
Best regards,
Tadayoshi
On Sat, Mar 6, 2021 at 4:41 AM Zoran Regvart <zo...@regvart.com> wrote:
> Hi Claus,
> I like the bash shell parameter expansion[1], this allows for
> specifying the default value if parameter doesn't expand. Something
> like {{speedUp:-}} would be optional without a default value, whereas
> {{speedUp:-other}} would provide `other` as a default value.
>
> For the REST producer bits I introduced optional parameters with a
> trailing question mark, see[2]. Doing something consistent here would
> be good I think.
>
> zoran
>
> [1]
> https://www.gnu.org/software/bash/manual/html_node/Shell-Parameter-Expansion.html#Shell-Parameter-Expansion
> [2]
> https://github.com/apache/camel/blob/b040a056ddf1b8f0756516cd47c00f180f128c05/core/camel-core/src/test/java/org/apache/camel/component/rest/RestProducerTest.java#L84
>
> On Fri, Mar 5, 2021 at 3:04 PM Claus Ibsen <claus.ib...@gmail.com> wrote:
> >
> > Hi
> >
> > In Camel 3.9 we are introducing optional property placeholders.
> > https://issues.apache.org/jira/browse/CAMEL-16302
> >
> > The use-case is to allow configuring Camel endpoints (primarily) where
> > you can specify some options that may be configured or not (optional).
> >
> > Currently all property placeholders are mandatory, unless a default
> > value is provided. So with the default value, you could do "optional"
> > but then you would need to know what the default value would be (if
> > there is any).
> >
> > Optional placeholders is also a feature that we want to have with
> > route templates (aka Kamelets). So you can create kamelets with a
> > number of options (some are required, and others would be optional).
> > And others have default values etc.
> >
> > The syntax for marking a property placeholder as option is to prefix
> > the key name with ?, eg
> >
> > from("jms:cheese?concurrentConsumers={{?speedUp}}")
> >
> > Here the concurrent consumers option is optional, as the placeholder
> > value starts with a ? in the key name.
> >
> > Then the Camel end user can configure the property placeholder, such
> > as in application.properties
> >
> > speedUp=5
> >
> > Or if there are no configuration, then the option is not present and
> > the endpoint is resolved as:
> >
> > from("jms:cheese")
> >
> >
> > The syntax with the ? mark was choose to keep it short. But we are
> > open for feedback.
> > Another alternative was to prefix with optional:
> >
> > {{optional:speedUp}}
> >
> > However the properties component in Camel then assume the key is named
> > optional, and the default value is speedUp. So it clashes with this.
> > But we could make "optional" a reserved word and do special handling
> > for this.
> >
> > The only concern about using ? is that an endpoint uri already have ?
> > for query parameters. And if using more ? would be confusing?
> >
> >
> from("jms:cheese?concurrentConsumers={{?speedUp}}&subscrtiptionName={{someName}}")
> >
> > Any thoughts?
> >
> >
> > --
> > Claus Ibsen
> > -----------------
> > http://davsclaus.com @davsclaus
> > Camel in Action 2: https://www.manning.com/ibsen2
>
>
>
> --
> Zoran Regvart
>
--
Tadayoshi Sato
