Reading an external property file for adapter configurations (How-To)

Question

One thing that has bugged me is having to change an Adapter's property settings in the context file and then build and re-deploy the bundle to effect those changes. This really becomes a problem when you want to test a bundle in different server environments (Development, QA, Staging) and then finally deploy that same bundle to Production. Here at EnerNOC, all those environments have different message servers and database schema names, making it a real challenge to insure you're building the same bundle each time for the different environments.
I played with a number of different ideas, but I wanted the solution to be Spring based. I finally settled on a rather simple solution to use external property files with the <util:properties/> tag of Spring, and then injecting the bean created from this into the adapters requiring different configurations.
First, in the context file, I needed to add a new Spring namespace - http://www.springframework.org/schema/util:
+<beans xmlns="http://www.springframework.org/schema/beans"+
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"*
xmlns:osgi="http://www.springframework.org/schema/osgi"*
xmlns:wlevs="http://www.bea.com/ns/wlevs/spring"*
xmlns:util="http://www.springframework.org/schema/util"*
xsi:schemaLocation="*
http://www.springframework.org/schema/beans*
http://www.springframework.org/schema/beans/spring-beans.xsd*
http://www.springframework.org/schema/osgi*
http://www.springframework.org/schema/osgi/spring-osgi.xsd*
http://www.springframework.org/schema/util*
http://www.springframework.org/schema/util/spring-util-2.5.xsd*
http://www.bea.com/ns/wlevs/spring*
http://www.bea.com/ns/wlevs/spring/spring-wlevs-v11_1_1_3.xsd">*
Next, I defined a bean for my property file:
+*<util:properties id="serverProperties" location="file:./applications/MyApplication/server.properties"/>*+
And then finally, I modified my adapter to inject a Properties object and use that to define the other properties in the Adapter:
+*<wlevs:adapter id="MyMessageAdapter" class="com.enernoc.cep.message.adapter.MyMessageAdapter" >*+
+*<wlevs:instance-property name="properties" ref="serverProperties"/>*+
+*<wlevs:listener ref="HAInputAdapter"/>*+         
+*</wlevs:adapter>*+
With this change, I can now build and deploy a bundle once to whatever servers I choose, and modify the server.properties file in each environment to make the necessary changes for message servers and databases. In a multi-server enviroment this becomes really handy as our deploy script needs to only create and push server.properties files and not new bundles.
As a nice-to-have feature someday, it would be great if Oracle could enable their <wlevs:/> namespace to recognize the Spring PropertyPlaceholderConfigurer feature, so that we could use placeholder variables for property values of <wlevs:/> specific tags.
Edited by: Jim Leary on Feb 28, 2011 4:11 PM
Edited by: Jim Leary on Feb 28, 2011 4:14 PM
Edited by: Jim Leary on Feb 28, 2011 4:15 PM
Edited by: Jim Leary on Feb 28, 2011 4:16 PM
Edited by: Jim Leary on Feb 28, 2011 4:17 PM
Edited by: Jim Leary on Feb 28, 2011 4:18 PM
Edited by: Jim Leary on Feb 28, 2011 4:19 PM

Answer 1

Jim,
You can use com.bea.wlevs.spring.support.ConfigurationPropertyPlaceholderConfigurer, which is based on org.springframework.beans.factory.config.PropertyPlaceholderConfigurer. For example,
<bean class="com.bea.wlevs.spring.support.ConfigurationPropertyPlaceholderConfigurer">
<property name="location" value="file:config/test.properties"/>
</bean>
<wlevs:adapter id="myAdapter" class="oracle.cep.sample.MyTestAdapter" >
<wlevs:instance-property name="serverAddress" value="${serverAddress}"/>
</wlevs:adapter>
Manju.