java - Using multiple property files (via PropertyPlaceholderConfigurer) in multiple projects/modules

Question

We are currently writing an application which is split into multiple projects/modules. For example, let's take the following modules:

• myApp-DAO
• myApp-jabber

Each module has its own Spring context xml file. For the DAO module I have a PropertyPlaceholderConfigurer which reads a property file with the necessary db connection parameters. In the jabber module I also have a PropertyPlaceHolderConfigurer for the jabber connection properties.

Now comes the main application which includes myApp-DAO and myApp-jabber. It reads all the context files and starts one big Spring context. Unfortunately it seems like there can only be one PropertyPlaceholderConfigurer per context, so whichever module gets loaded first is able to read it's connection parameters. The other one throws an exception with an error like "Could not resolve placeholder 'jabber.host'"

I kind of understand what the problem is, but I don't really know a solution - or the best practice for my usecase.

How would I configure each module so that each one is able to load its own property file? Right now I've moved the PropertyPlaceHolderConfigurer out of the seperate context files and merged them into the main application's context (loading all property files with a single PropertyPlaceHolderConfigurer). This sucks though, because now everyone who uses the dao module has to know, that they need a PropertyPlaceHolderConfigurer in their context .. also the integration tests in the dao module fail etc.

I'm curious to hear about solutions/ideas from the stackoverflow community..

Answer 1

If you ensure that every place holder, in each of the contexts involved, is ignoring unresolvable keys then both of these approaches work. For example:

<context:property-placeholder
location="classpath:dao.properties,
          classpath:services.properties,
          classpath:user.properties"
ignore-unresolvable="true"/>

or

    <bean id="propertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
        <property name="locations">
            <list>
                <value>classpath:dao.properties</value>
                <value>classpath:services.properties</value>
                <value>classpath:user.properties</value>
            </list>
        </property> 
        <property name="ignoreUnresolvablePlaceholders" value="true"/>
    </bean>