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From Paul Duffin <pduf...@volantis.com>
Subject Re: Serializer and SitemapModelComponent
Date Wed, 27 Nov 2002 19:43:19 GMT
Carsten Ziegeler wrote:
>>Paul Duffin wrote:
> 
> 
>>Why is the Serializer not an instance of SitemapModelComponent when both
>>generators and transformations are ?
>>
>><snip/>
>>
>>The following link shows a discussion which took place in April this
>>year which seemed to indicate that this was going to be changed but
>>unfortunately it does not seem to have changed at all.
>>
>>http://www.mail-archive.com/cocoon-dev@xml.apache.org/msg14047.html
>>
> 
> Yes, this discussion was held several times - now, if you can come up
> with a solution which is compatible, which means that this solution does 
> not break already existing serializers.
> 

If all existing Serializers extend AbstractSerializer then you could 
make the Serializer interface implement the SitemapModelComponent and 
simply add an empty setup method to the AbstractSerializer.

If only binary compatability is required then the code which calls the 
setup method could catch NoSuchMethodError.

If source compatability is also required then you could create a 
SerializerSitemapModelComponent interface which extends Serializer and 
implements SitemapModelComponent. The code which initializes the 
Serializer in AbstractStreamPipeline would check before it casted the 
Serializer to a SitemapModelComponent and called the setup method.

If you do not want to create the SerializerSitemapModelComponent 
interface (which thinking about it is probably a bad idea) you could 
just document that if a Serializer implements SitemapModelComponent then 
its setup method will be called. You could also say that in future the 
Serializer interface will be extended to implement the 
SitemapModelComponent and anyone writing their own Serializer which does 
not extend AbstractSerializer would then have the time to implement the 
interface and provide a dummy setup method. They could do this 
immediately without breaking backwards compatability.

The AbstractSerializer class should in any case be modified to implement 
SitemapModelComponent and implement a dummy setup method.

Eventually the Serializer interface could be modified and the extra 
checks removed from the AbstractStreamPipeline.

I have only spent less than a day looking at the code so there may be 
all sorts of implications which I have not considered but based on what 
I know the above seems like a workable solution.


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