Optional @PropertySource location

Question

I'm using Spring 3.2 in a web application and I'd like to have a .properties file within the classpath which contains default values. The user should be able to use JNDI to define a location where another .properties is stored which overrides the default values.

The following works as long as the user has set the configLocation as JNDI property.

@Configuration
@PropertySource({ "classpath:default.properties", "file:${java:comp/env/configLocation}/override.properties" })
public class AppConfig
{
}

However, the external overrides should be optional and so should the JNDI property.

Currently I get an exception (java.io.FileNotFoundException: comp\env\configLocation\app.properties (The system cannot find the path specified) when the JNDI property is missing.

How can I define optional .properties that are used only when the JNDI property (configLocation) is set? Is this even possible with @PropertySource or is there another solution?

Answer 1

As of Spring 4, issue SPR-8371 has been solved. Consequently, the @PropertySource annotation has a new attribute called ignoreResourceNotFound that has been added for exactly this purpose. Additionally, there is also the new @PropertySources annotation which allows implementations like:

@PropertySources({
    @PropertySource("classpath:default.properties"),
    @PropertySource(value = "file:/path_to_file/optional_override.properties", ignoreResourceNotFound = true)
})

Answer 2

If you're not yet on Spring 4 (see matsev's solution), here's a more verbose, but roughly equivalent solution:

@Configuration
@PropertySource("classpath:default.properties")
public class AppConfig {

    @Autowired
    public void addOptionalProperties(StandardEnvironment environment) {
        try {
            String localPropertiesPath = environment.resolvePlaceholders("file:${java:comp/env/configLocation}/override.properties");
            ResourcePropertySource localPropertySource = new ResourcePropertySource(localPropertiesPath);
            environment.getPropertySources().addLast(localPropertySource);
        } catch (IOException ignored) {}
    }

}