[jira] [Commented] (CAMEL-10572) RefLanguage should support Predicates for Choice

["Claus Ibsen (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/CAMEL-10572?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15733280#comment-15733280 ] 

Claus Ibsen commented on CAMEL-10572:
-------------------------------------

You are welcome to work on a patch or better githb PR with an implementation of this
http://camel.apache.org/contributing

Include an unit test would be good

> RefLanguage should support Predicates for Choice
> ------------------------------------------------
>
>                 Key: CAMEL-10572
>                 URL: https://issues.apache.org/jira/browse/CAMEL-10572
>             Project: Camel
>          Issue Type: Improvement
>          Components: camel-core
>    Affects Versions: 2.18.1
>            Reporter: Christoph Läubrich
>            Priority: Minor
>             Fix For: 2.19.0
>
>
> The documentation for the CBR (http://camel.apache.org/content-based-router.html) states 
> {quote}The following example shows how to route ... depending on the evaluation of various Predicate expressions{quote}
> If you now look at the predicate section (http://camel.apache.org/predicate.html) it says:
> {quote}Camel supports extensible Predicates using multiple Languages; the following languages are supported out of the box
> ...
> Ref Language
> ...{quote}But going to the Ref page (http://camel.apache.org/ref-language.html) it states{quote}The Ref Expression Language is really just a way to lookup a custom Expression from the Registry. {quote}
> So Ref Language does NOT support Predicates, it works in most cases since nearly all classes in Camel core implement Expresion and Predicate interface and there is a lot of converting between those, but if you have a custom expression that only implements predicate, you get in fact an (a bit misleading) exception:
> {quote}java.lang.IllegalArgumentException: Cannot find expression in registry with ref: predicate
> 	at org.apache.camel.language.ref.RefLanguage$1.evaluate(RefLanguage.java:50)
> 	at org.apache.camel.support.ExpressionAdapter.evaluate(ExpressionAdapter.java:36)
> 	at org.apache.camel.support.ExpressionSupport.matches(ExpressionSupport.java:32)
> 	at org.apache.camel.util.ExpressionToPredicateAdapter.matches(ExpressionToPredicateAdapter.java:35)
> 	at org.apache.camel.processor.FilterProcessor.matches(FilterProcessor.java:65)
> 	at org.apache.camel.processor.ChoiceProcessor.process(ChoiceProcessor.java:93)
> 	at org.apache.camel.management.InstrumentationProcessor.process(InstrumentationProcessor.java:77)
> 	at org.apache.camel.processor.RedeliveryErrorHandler.process(RedeliveryErrorHandler.java:542)
> 	at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:197)
> 	at org.apache.camel.processor.CamelInternalProcessor.process(CamelInternalProcessor.java:197)
> 	at org.apache.camel.component.timer.TimerConsumer.sendTimerExchange(TimerConsumer.java:192)
> 	at org.apache.camel.component.timer.TimerConsumer$1.run(TimerConsumer.java:76){quote}
> It takes me some time to find out that Camel is in fact finding my bean but can't use it, beside that its hard to work out why a predicate must also implement expression (Choice it self requires an Predicate in fact, so it converts all expresions to Predicates).
> So the following improvements would be nice
> # Let RefLanguage send out some kind of TypeConverterException if it can't use the bean as the desired type
> # Let Ref, if it finds that the referenced bean is a predicate, convert this to an expression e.g with PredicateToExpressionAdapter



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