StringSearchInterpolator interpolator = new StringSearchInterpolator( "${", "}" );
// interpolation as plexus did it before
interpolator.addValueSource( new PropertiesBasedValueSource( System.getProperties() ) );
String interpolatedProps = interpolator.interpolate( properties );
logger.debug( "Loading configuration into commons-configuration, xml {}", interpolatedProps );
builder.load( new StringReader( interpolatedProps ) );
configuration = builder.getConfiguration( false );
configuration.setExpressionEngine( expressionEngine );