In the Internet of Things, billions of networked and software- driven devices will be connected to the Internet. They can communicate and cooperate with each other to function as a composite system. This paper proposes the AMG (abstract, model and generate) method for the development of such composite systems. With AMG, the development of software application can be done in an automatic manner, and therefore reducing the cost and develpment time. The method has been prototyped and tested with use cases.