ModelInterpolationException error = AccessController.doPrivileged(action);

            if (error != null) {
                throw error;
            }
        } finally {
            getInterpolator().clearAnswers();
        }
    }

    protected Interpolator createInterpolator() {
        StringSearchInterpolator interpolator = new StringSearchInterpolator();
        interpolator.setCacheAnswers(true);

            return interpolateInternal(src, valueSources, postProcessors, debug);
        } finally {
            interpolator.clearAnswers();
        }
    }

    protected List<ValueSource> createValueSources(
            final Model model, final File projectDir, final ProjectBuilderConfiguration config) {