add util class which maintains the layer of model.

Change-Id: I67d85a5dfcbd546497b3c53e50c0afe38242347e
Signed-off-by: Sharl <amoiz.shine@gmail.com>
remove trash code.

Change-Id: I6cf80adff944dee66b96fc016c30148698656c92
Signed-off-by: Sharl <amoiz.shine@gmail.com>