public List<String> evaluate( String function, List<String> parameters ) {
List<String> results = null;
UrlRewriteFunctionProcessor processor = functions.get( function );
if( processor != null ) {
try {
results = processor.resolve( UrlRewriteContextImpl.this, parameters );
} catch( Exception e ) {
LOG.failedToInvokeRewriteFunction( function, e );
results = null;
}
}