Function-Templates for Synapse Configuration
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Key: SYNAPSE-738
URL: https://issues.apache.org/jira/browse/SYNAPSE-738
Project: Synapse
Issue Type: New Feature
Components: Core
Affects Versions: FUTURE
Reporter: Udayanga Wickramasinghe
Implementing Function templates in Synapse can be used to reduce lot of
complexity as well as eliminate redundancy at synapse configuration. At the
moment a large portion of ESB configuration are at the micro level. Because of
this users have to individually configure each and every mediator to achieve
some high level task. But what we need is a high level abstraction that users
can easily use to model such scenarios .
For example if we consider following scenario ,
<proxy name="SplitAggregateProxy">
<target>
<inSequence>
<iterate expression="//m0:getQuote/m0:
request"
preservePayload="true"
attachPath="//m0:getQuote"
xmlns:m0="http://services.samples";>
<target>
<sequence>
<send>
<endpoint>
<address
uri="http://localhost:9000/services/SimpleStockQuoteService"/>
</endpoint>
</send>
</sequence>
</target>
</iterate>
</inSequence>
<outSequence>
<aggregate>
<onComplete expression="//m0:getQuoteResponse"
xmlns:m0="http://services.samples";>
<send/>
</onComplete>
</aggregate>
</outSequence>
</target>
</proxy>
Here what user really wants to look at is three configuration parameters ,
1. Two XPath expressions
2. An endpoint address
we can hide a lot of this complexity by introducing a 'template' configuration
that parameterize (like a function does) a known pattern such as this
one.Parameterization can be done using xpath expressions..
Function templates will look like following in synapse config,
1)
<template name="[func name]">
/**parameters for this function template**/
<parameter name="p1" />*
/**any sequence**/
<any sequence>+
</template>
-->A Template is an extension of Sequence , hence template body can contain any
sequence in general
--> any mediator/comp inside template body can refer to its parameters just
like a normal function does ,by xpath function scope (ie:-func) variable
ie:- <aggregate>
<onComplete xmlns:m0="http://services.samples";
expression="$func:p2">
<log level="full" />
<send/>
</onComplete>
</aggregate>
OR
<log level="custom">
<property name="p1-value" expression="$func:p1"/>
<property name="p2-value"
expression="get-property('func','p2')"/>
</log>
2)To invoke a template in synapse we can define a Invoke mediator which will be
in the following form. Using a invoke mediator ,from within any sequence of
Synapse we would be able to execute a template with the passed on values for
parameters such as p1,p2,etc.... :
<invoke target="[target func template]">
<parameter name="p2" value="{any xpath} | plain-value"/>*
</invoke>
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