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From Supun Kamburugamuva <>
Subject Re: Constant/reproducable order of elements in synapse.xml
Date Mon, 09 Nov 2009 04:45:49 GMT
Hi Eric,

I thought about this a bit further. Synapse runs on an object model. Not on
a XML configuration. As far as I understood this was the original goal. Also
it makes sense. The synapse configuration can be created using XML or may be
spring or may be pure programming. At the synapse object model layer I think
it is logical to use a hash map. If a particular serialization and building
wants to have an order it is the responsibility of the build and serialize
method writer to impose it.

Isn't there a way to impose this at the serialize and builder level?


On Sun, Nov 8, 2009 at 2:22 AM, Hubert, Eric <>wrote:

>  Hi Supun,
> Please see my comments inline!
> Synapse language is treated as a programming language at least for the out
> side world. For example sequences can be attributed to functions. In any
> programming language the order in which these symbols occur does not matter
> as long as the symbols can be found by the caller.
> Agreed.
> So I have doubts in implementing an order for the synapse elements. By
> order I meant something like all the sequences are at the top then the proxy
> services etc.
> I share these doubts, but you describe exactly the current implementation.
> Please have a look at:
> SynapseXMLConfigurationSerializer.serializeConfiguration(SynapseConfiguration
> synCfg). It uses a fixed order of top level elements.
> Specific element serializers are then using an order depending on the way
> the configuration has been stored in memory. Mostly the XML information will
> be transferred to strongly typed data structures. While deserializing those
> values, currently a fixed order will be used. This might be different, from
> the one originally read in. Some list like structures are stored to
> unordered Map-Implementations for faster key-value access. While
> deserializing those values you end up with a random order. I think that this
> part could be fixed rather easily by using LinkedHashMap preserving the key
> order in which entries have been added to the map.
> When a user types in the synapse.xml, we should be able to preserve the
> order in which they have entered the elements in the synapse.xml. If you
> meant this one I'm +1 for implementing it.
> I also agree this would be the most desirable option, although the current
> implementation seems to be very far a way from that. Each factory/serializer
> pair would need to be designed for this purpose (e.g. keep a list or list of
> linked maps or any suitable structure of read elements/attributes, store it
> for deserialization purposes only and use this to retrieve the values in the
> exact order from structured object structures). I guess only something like
> this could warrant a working round-trip serialization/deserialization where
> the user may modify any part of the configuration, insert new stuff at any
> allowed place and this exact order will be preserved during later
> deserializations.
> So my concrete suggestion for a start was just to replace all class member
> implementations of SynapseConfiguration which are currently of type HashMap
> with LinkedHashMap. From my point of view this is at least an improvement.
> No pain, big gain? ;-)
> Regards,
>     Eric

Software Engineer, WSO2 Inc

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