In this paper, we introduce a framework for the automatic configuration of applications running in dynamic environments where changes are frequent. We propose a way to describe, for each application, its configuration policy, and the execution environments factors that affect its behavior. On this basis, we can generate application-specific configuration tools, called conflets. The applications source code is not required. The conflet combines the information drawn from the execution environment with the knowledge of the configuration policy. It is therefore able to detect when and how the execution environment modifies its characteristics, and can automatically react by reconfiguring the application and thus adapting it to the dynamic environment.