Spring Environment Property Source Configuration

Question

I'm working on an application library with a utility class called "Config" which is backed by the Spring Environment object and provides strongly typed getters for all the applications configuration values.

The property sources for the configuration can vary depending on environment (DEV/PROD) and usage (standalone/test/webapp), and can range from the default ones (system & env props) to custom database and JNDI sources.

What I'm struggling with is how to let the apps consuming this library easily configure the property source(s) used by Environment, such that the properties are available for use in our Config class and via the PropertySourcesPlaceholderConfigurer.

We're still using XML configuration, so ideally this could be configured in XML something like.

<bean id="propertySources" class="...">
    <property name="sources">
        <list>
            <ref local="jndiPropertySource"/>
            <ref local="databasePropertySource"/>
        </list>
    </property>
</bean>

...and then injected somehow into the Environment's property sources collection.

I've read that something like this may not be possible due to the timing of the app context lifecycle, and that this may need to be done using an application initializer class.

Any ideas?

Answer 1

It depends on how you want to use the properties, if it is to inject the properties using ${propertyname} syntax, then yes just having PropertySourcesPlaceHolderConfigurer will work, which internally has access to the PropertySources registered in the environment.

If you plan to use Environment directly, using say env.getProperty(), then you are right - the properties using PropertySourcesPlaceHolderConfigurer are not visible here. The only way then is to inject it using Java code, there are two ways that I know of:

a. Using Java Config:

@Configuration
@PropertySource("classpath:/app.properties")
public class SpringConfig{

}

b. Using a custom ApplicationContextInitializer, the way it is described here