property-placeholder location from another property

Question

Hi

I need to load some properties into a Spring context from a location that I don't know until the program runs.

So I thought that if I had a PropertyPlaceholderConfigurer with no locations it would read in my.location from the system properties and then I could use that location in a context:property-placeholder

Like this

<bean class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer"/>    
<context:property-placeholder location="${my.location}"/>

but this doesn't work and nor does location="classpath:${my.location}"

Paul

Answer 1

The problem here is that you're trying to configure a property place holder using property placeholder syntax :) It's a bit of a chicken-and-egg situation - spring can't resolve your ${my.location} placeholder until it's configured the property-placeholder.

This isn't satisfactory, but you could bodge it by using more explicit syntax:

<bean class="org.springframework.beans.factory.config.PropertyPlaceHolderConfigurer">
   <property name="location">
      <bean class="java.lang.System" factory-method="getenv">
         <constructor-arg value="my.location"/>
      </bean>
   </property>
</bean>

Answer 2

You can do this with a slightly different approach. Here is how we configure it. I load default properties and then overrided them with properties from a configurable location. This works very well for me.

<bean id="propertyPlaceholderConfigurer"
     class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
     <property name="systemPropertiesModeName" value="SYSTEM_PROPERTIES_MODE_OVERRIDE" />
     <property name="locations">
      <list>
       <value>classpath:site/properties/default/placeholder.properties
       </value>
       <value>classpath:site/properties/${env.name}/placeholder.properties
       </value>
      </list>
     </property>
    </bean>