how does ${runtime} work?

[Abdur Muhammed]

One of the applications i'm working on uses spring beans to access the properties file. I would like to know where the application picks up the ${runtime} value from

<bean id="propertyConfigurer"
		class="com.britannica.spring.extensions.properties.ExposablePropertyPaceholderConfigurer">
		<property name="locations">
			<list>
				<value>
					classpath:com/britannica/learningzone/webapp/${runtime}/learning-zone-webapp.properties
				</value>
			</list>
		</property>
		<property name="systemPropertiesModeName"
			value="SYSTEM_PROPERTIES_MODE_OVERRIDE" />
		<property name="order" value="1" />
	</bean>

Thanks