private String sourceLevel = USER_LEVEL;
    private boolean sourceLevelSet = false;

    public void setSourceLevel(String sourceLevel) {
        if (sourceLevelSet) {
            throw new IllegalStateException("Cannot reset sourceLevel attribute; it is already set to: " + sourceLevel);
        } else if (!(USER_LEVEL.equals(sourceLevel) || PROJECT_LEVEL.equals(sourceLevel)  || GLOBAL_LEVEL.equals(sourceLevel))) {