Methods and apparatus, including computer program products, implement a hierarchical arrangement of class loaders. Each class loader has a naming token, and each token driven class loader has one or more delegation tokens. A class definition request is received in a first, token driven class loader. If the first class loader has a parent class loader, the class definition is requested from the parent. If the parent is a token driven class loader, delegation tokens are used to delegate the class definition request to the parent. If the class definition is not obtained from a parent class loader, an attempt is made to obtain the class definition from the resources of the first class loader. If that also fails, the delegation tokens of the first class loader are used to find a matching child class loader and the class definition is requested from the matching child class loader.