This paper reports the development of D-Raje (Distributed Resource-Aware Java Environment), a Java-based middleware platform that makes it possible to model and to monitor resources in a distributed environment. With this middleware, any kind of hardware or software resource can be modelled using standard Java objects, and services allow to discover local as well as remote resources, and to observe the state of these resources either locally or remotely. D-Raje is meant to ease the development of adaptive, security-oriented, or QoS-oriented Java applications, as well as the development of platforms capable of supporting such demanding applications.