Is there a way to specify a default property value in Spring XML?

Question

We are using a PropertyPlaceholderConfigurer to use java properties in our Spring configuration (details here)

eg:

<foo name="port">   <value>${my.server.port}</value> </foo> 

We would like to add an additional property, but have a distributed system where existing instances could all use a default value. Is there a way to avoid updating all of our properties files, by indicating a default value in the Spring config for when there isn't an overriding property value defined?

Answer 1

Spring 3 supports ${my.server.port:defaultValue} syntax.

Answer 2

There is a little known feature, which makes this even better. You can use a configurable default value instead of a hard-coded one, here is an example:

config.properties:

timeout.default=30 timeout.myBean=60 

context.xml:

<bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">     <property name="location">         <value>config.properties</value>     </property> </bean>  <bean id="myBean" class="Test">     <property name="timeout" value="${timeout.myBean:${timeout.default}}" /> </bean> 

To use the default while still being able to easily override later, do this in config.properties:

timeout.myBean = ${timeout.default}