[Springframework-developer] custom XML config files

[<jas...@ma...>]

The Spring XML config file is cool and flexible; but for constrained 
problems it can be a little verbose. For certain scenarios I'd like to 
provide some neater, more concise XML syntax.

e.g. I'm considering configuring the ActiveMQ JMS message broker using 
Spring's configuration mechanism, but I'd prefer to be able to use some 
well defined aliases/macros in the config file - while preserving the 
full power of Spring's XML.

The basic idea is to use the default bean/property/value type syntax 
for Spring and add some context-specific macros (elements) which map 
directly onto specific well known bean factories - always allowing 
folks to drop down to the default Spring XML if they need to, so that 
we...

* reduce typing hugely
* to allow an XSD or DTD to be created to (i) validate the incoming XML 
and (ii) to auto-document the various properties available easily
* preserve the extensible & flexible nature of Spring's XML


This would be especially useful for configuring large services which 
want to have their own configuration mechanisms (like a message broker 
or other custom kinds of container). Having a little schema optimised 
for the problem space would really help


Here's an example of the kind of thing I mean, where we'd add a few new 
elements which the ActiveMQ-specific parser would understand...

<container name="foo">

     <!-- macros of some kind that ActiveMQ knows about -->
     <connector url="tcp://localhost:61616"/>
     <connector url="multicast://228.1.2.3.4:5000"/>

     <messageStore class="Foo">
	<!-- inside here drop down to Spring XML to customize some plugin -->
	<property name="cheese"><value>123</value></property>
     </messageStore>
</container>


Using the example above we could use a simple macro which turns

     <connector url="..." timeout="2000"/>

into

     <bean class="MyConnectorBean">
	<property name="url"><value>...</value></property>
	<property name="timeout"><value>2000</value></property>
     </bean>

This could be a trivial optional transformation step written in a 
little Java code, where the ActiveMQXmlBeanFactory could derive from 
the Spring XmlBeanFactory and install a custom transformer into the 
XmlBeanDefinitionReader so that any XML notation the ActiveMQ factory 
knew about could be transformed into normal Spring XML ready for Spring 
to do its thing.

I'm thinking the easiest way to do it could be to allow custom 
XmlBeanDefinitionReader implementations to be registered with an 
XmlBeanFactory via some constructor or protected method (e.g. either a 
setter method or create the XmlBeanDefinitionReader by lazy 
construction inside the XmlBeanFactory), then I could just provide my 
own custom XmlBeanDefinitionReader derivation which implements the 
macros I need - all used inside my own ActiveMQXmlBeanFactory which 
extends XmlBeanFactory.

I wondered if folks had tried this kinda thing yet? If folks agree - 
could we have the constructor or XmlBeanDefinitionReader setter/lazy 
create method on XmlBeanFactory please?

James
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