In component-based software systems, sometimes it is difficult to find a single component implementation that satisfies requirements concerning multiple qualities. However, it is possible to compose multiple implementations with identical functions but different qualities to satisfy the requirement. The keys to the composition include (a) finding out the requirement which requires the composition and (b) the design of composition policy to ensure the desired qualities. In this paper, we present an approach consisting of three steps to the composition of component implementations. The identification step leverages some analysis method to find out the necessity of composition as well as the according candidate implementations. The policy design step is responsible for the design and description of composition policies, which are proved to provide the desired qualities. The implementation step carries out the designed policies. The last two steps can be automated to a certain degree. The example of Java Pet Store demonstrates the approach.