title: Make IntelliJ aware of a properties file
body: <p>Is there some way to tell IntelliJ that a particular <code>.properties</code> file will be loaded into a project's environment?  We use <code>@PropertySource</code> annotations to load properties files, and in several places load override values from a file determined by an already-configured property, like so:</p>
  
  <pre><code>@Configuration
  @PropertySource("classpath:com/example/package/db.properties")
  @PropertySource("classpath:com/example/package/db.${db.instance}.properties")
  public class DatabaseConfig {
      private @Value("${db.someProperty}") String someDBProperty;
      // ...
  }
  </code></pre>
  
  <p>The problem is that within one of these indirectly referenced files, e.g. <code>db.test.properties</code>, IntelliJ doesn't know if/how the properties file is referenced, so it can't tie any of the entries to their usages.  (Bizarrely, <em>some</em> of the properties listed in these files are not greyed out to indicate 'Unused property', though even these give no results for a 'Find usages' search).  There is no issue with directly named files, e.g. <code>db.properties</code> above.</p>
  
  <p>Is there some way to tell IntelliJ about these files short of creating additional dummy <code>@Configuration</code> files that reference them?</p>