wro4j-core/src/main/java/ro/isdc/wro/manager/factory/ConfigurableWroManagerFactory.java
private void updatePropertiesWithConfiguration(final Properties props, final String key) {
    final FilterConfig filterConfig = Context.get().getFilterConfig();
    // first, retrieve value from init-param for backward compatibility
    final String valuesAsString = filterConfig.getInitParameter(key);
    if (valuesAsString != null) {
      props.setProperty(key, valuesAsString);
    } else {
      // retrieve value from configProperties file
      final String value = getConfigProperties().getProperty(key);
      if (value != null) {
        props.setProperty(key, value);
      }
    }
  }
private void updatePropertiesWithConfiguration(final Properties props, final String key) {
    final FilterConfig filterConfig = Context.get().getFilterConfig();
    // first, retrieve value from init-param for backward compatibility
    final String valuesAsString = filterConfig.getInitParameter(key);
    if (valuesAsString != null) {
      props.setProperty(key, valuesAsString);
    } else {
      // retrieve value from configProperties file
      final String value = getConfigProperties().getProperty(key);
      if (value != null) {
        props.setProperty(key, value);
      }
    }
  }
Add to properties a new key with value extracted either from filterConfig or from configurable properties file.
This method helps to ensure backward compatibility of the filterConfig vs configProperties configuration.

@param props
the {@link Properties} which will be populated with the value extracted from filterConfig or
configProperties for the provided key.
@param key
to read from filterConfig or configProperties and put into props.