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Date: Wed, 18 Apr 2012 09:59:59 +0200
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Subject: Re: [HEADS UP] - TypeConverter improved in Camel 2.10
From: Bengt Rodehav <bengt@rodehav.com>
To: dev@camel.apache.org
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+1

I've just spent two days trying to figure out what I did wrong. I  had a
case where all subsequent xml conversions would fail after I tried to
process one xml message in invalid format. Then I found your post. Good job
fixing it.

/Bengt

2012/4/17 Christian M=FCller <christian.mueller@gmail.com>

> +1,
>
> and thanks for your hard work...
>
> Best,
> Christian
>
> On Tue, Apr 17, 2012 at 11:38 AM, Claus Ibsen <claus.ibsen@gmail.com>
> wrote:
>
> > Hi
> >
> > I am inclined to backport these changes to the 2.9 branch as I think
> > the bug from CAMEL-5164 would bite other people as well.
> > I have a workaround patch for 2.9 branch as work in progress. But I
> > dont feel its an optimal solution, as would the backport of the
> > changes from 2.10.
> >
> > There is only a slight API change in TypeConverter. Most people would
> > use the @Converter for their custom converters, and if so, then they
> > are okay (no problem there). Only for people who implement the
> > TypeConverter directly, and then add that directly to the
> > TypeConverterRegistry API. Frankly I dont see this used at all by end
> > users (The @Converter is mich simpler).
> >
> > However there is a slight change in the API from Message.getBody(type)
> > and Message.getHeader(name, Type), as they would now throw a
> > TypeConversionException if failing. Where as beforehand a WARN would
> > be logged and null returned.
> >
> > IMHO the changes from 2.10 is better and also allows end users to be
> > in control of the failure first-hand. And frankly also what I would
> > expect from the call.
> >
> > If nobody scream, then we should get this backported for the next 2.9.3
> > release.
> >
> > Any thoughts?
> >
> >
> > PS: I have attached my ugly workaround patch. We can use that as a
> > backup if someone scream really loud.
> >
> >
> >
> > On Tue, Apr 17, 2012 at 7:46 AM, Claus Ibsen <claus.ibsen@gmail.com>
> > wrote:
> > > Hi
> > >
> > > Recently I have spent some time to improve the type converters in Cam=
el
> > 2.10.
> > >
> > > Most significant is the following changes
> > > a) fix important bug
> > > b) Fail fast
> > > c) tryConvertTo
> > > d) Expose utilization statistics
> > >
> > >
> > > Ad a)
> > > A bug was reported in https://issues.apache.org/jira/browse/CAMEL-516=
4
> > >
> > > In summary if using camel-jaxb that offers a fallback type converter,
> > > and a failure occurs during XML marshalling,
> > > then subsequent new XML messages may fail, despite they were okay.
> > >
> > > Ad b)
> > > Due to a we need to detect this faster and better. So now the type
> > > converter system in Camel will fail fast
> > > by throwing a new TypeConversionException (its runtime). That allows
> > > Camel to detect the (a) failure faster
> > > from a fallback type converter (regular non fallback would fail fast
> > already)
> > >
> > > This means the API is also consistent from caller point of view. You
> > > get a TypeConversionException if there
> > > was a failure during a type conversion attempt.
> > >
> > > Ad c)
> > > There is some places in camel-core where we want to only try to
> > > convert. For example with the binary predicates
> > > where you want to compare if X > Y. Then we try to coerce X and Y to
> > > numeric values.
> > >
> > > Likewise there is a few other spots where we do this, such as the XSL=
T
> > > component, where we try to use StAX, SAX, before DOM etc.
> > > So we have introduced a tryConvertTo API, which would not fail during
> > > type conversion.
> > >
> > > Ad d)
> > > The type converter system is used a lot in Camel during routing
> > > messages. Now we expose utilization statistics,
> > > which allow end users to spot if there is too many missing type
> > > conversion attempts. For example a route may attempt to convert, wher=
e
> > > there is no suitable type converter. This can now more easily be
> > > spotted, allowing the end user to either. Implement such a missing
> > > type converter, or
> > > correct a mistake in his application or the likes.
> > >
> > > The statistics is exposed in JMX and as well when Camel shutdown as a
> > log line.
> > >
> > >
> > >
> > >
> > > On another note I am also hunting down to avoid using the
> > > PropertiesEditorTypeConverter, as it has many flaws
> > > - its not thread safe
> > > - its slow
> > > - and 3rd party projects can add property editors that influence
> > > Camel's type converts (eg ActiveMQ has a String -> List) properties
> > > editor that turns a String into a List of ActiveMQDestination
> > > instances.
> > > - it does not understand generics in List/Collection type, eg the
> > > ActiveMQ example above
> > >
> > > And basically we uses it only in Camel for doing some of the simpler
> > > basic conversions: String <-> Numeric. And so forth. But over the tim=
e
> > > we have added those as type converter directly in Camel, as they are
> > > faster as well.
> > >
> > >
> > >
> > >
> > > --
> > > Claus Ibsen
> > > -----------------
> > > CamelOne 2012 Conference, May 15-16, 2012: http://camelone.com
> > > FuseSource
> > > Email: cibsen@fusesource.com
> > > Web: http://fusesource.com
> > > Twitter: davsclaus, fusenews
> > > Blog: http://davsclaus.blogspot.com/
> > > Author of Camel in Action: http://www.manning.com/ibsen/
> >
> >
> >
> > --
> > Claus Ibsen
> > -----------------
> > CamelOne 2012 Conference, May 15-16, 2012: http://camelone.com
> > FuseSource
> > Email: cibsen@fusesource.com
> > Web: http://fusesource.com
> > Twitter: davsclaus, fusenews
> > Blog: http://davsclaus.blogspot.com/
> > Author of Camel in Action: http://www.manning.com/ibsen/
> >
>

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