How to reference an ${ENV} var in a propertyConfigurer bean?

I'm trying to modify this example for my own purposes.

I want to load the properties from a server-specific file, using something like this:

<beans:bean id="propertyConfigurer"
    class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <beans:property name="locations">
        <beans:list>
            <beans:value>${ENV_JDBC_CONFIG}</beans:value>
        </beans:list>
    </beans:property>
</beans:bean>

Where ENV_JDBC_CONFIG is an enrivonment variable specifying a path to a properties file.

This fails with

`java.io.FileNotFoundException: Could not open ServletContext resource [/${ENV_JDBC_CONFIG}]`

How can I accomplish what I'm trying to do here?