How to collect spring properties from multiple files for use on a single bean

Question

I haven't gotten my head wrapped around Spring yet, so correct me if this question doesn't make sense...

I have a PropertyPlaceholderConfigurer

<bean id="rdbmPropertiesPlacholder" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer" lazy-init="false">
    <property name="location" value="classpath:/properties/rdbm.properties" />
</bean>

And I have a bean being injected I guess?

<bean id="PortalDb" class="org.apache.commons.dbcp.BasicDataSource">
    <property name="driverClassName" value="${hibernate.connection.driver_class}" />
    <property name="url" value="${hibernate.connection.url}" />
    <property name="username" value="${hibernate.connection.username}" />
    <property name="password" value="${hibernate.connection.password}" />
    ...

What I want is a second placeholder pointing to a different properties file with the username/password so that I can split up the properties into two different files. Then the database connection information can be separate from the db username/password, and I can source control one and not the other.

I've tried basically copying the rdbmPropertiesPlaceholder with a different id and file and trying to access the properties, but it doesn't work.

This code is from the uPortal open source web portal project.

Answer 1

Using this notation lets you specify multiple files:

 <bean id="rdbmPropertiesPlacholder" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer" lazy-init="false">
     <property name="locations">
       <list>
           <value>classpath:/properties/rdbm.properties</value>
           <value>classpath:/properties/passwords.properties</value>
       </list>
    </property>
 </bean>

The propertyplaceholderconfigurerer just merges all of these to look like there's only one, so your bean definitions do not know where the properties come from.

Answer 2

The org.springframework.beans.factory.config.PropertyPlaceholderConfigurer can do this (as already answered. What you may want to do is make use of the name spacing so that you can refer to same-named properties from both files without ambiquity. For your example, you can do this:

<bean id="generalPropertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="location" value="classpath:/properties/general.properties"/>
</bean>

<bean id="db.PropertyConfigurer" class="org.springframework.beans.factory.config.PropertyPlaceholderConfigurer">
    <property name="location" value="classpath:/properties/rdbm.properties" />
    <property name="placeholderPrefix" value="$db{" />
    <property name="placeholderSuffix" value="}" />  
</bean>

In your context files, you can now refer to general properties with ${someproperty}, and refer to rdbm properties with $db{someproperty}.

This will make your context files much cleaner and clearer to the developer.