how to read System environment variable in Spring applicationContext

How to read the system environment variable in the application context?

I want something like :

<util:properties id="dbProperties"
        location="classpath:config_DEV/db.properties" />

or

<util:properties id="dbProperties"
        location="classpath:config_QA/db.properties" />

depending on the environement.

Can I have something like this in my application Context?

<util:properties id="dbProperties"
        location="classpath:config_${systemProperties.env}/db.properties" />

where the actual val is set based on the SYSTEM ENVIRONMENT VARIABLE

I'm using Spring 3.0