We are using a PropertyPlaceholderConfigurer to use java properties in our Spring configuration (details here)
eg:
Are you looking for the PropertyOverrideConfigurer documented here
http://static.springsource.org/spring/docs/2.5.x/reference/beans.html#beans-factory-overrideconfigurer
The PropertyOverrideConfigurer, another bean factory post-processor, is similar to the PropertyPlaceholderConfigurer, but in contrast to the latter, the original definitions can have default values or no values at all for bean properties. If an overriding Properties file does not have an entry for a certain bean property, the default context definition is used.