1. An apparatus comprising: one or more computer readable storage media; and program instructions stored on the one or more computer readable storage media and comprising a code service that, when executed by a processing system implemented within a single processing device, directs the processing system to at least: receive a request message communicated by an application component via a message interface in an application environment hosted by the processing system at a layer above a target environment hosted by the processing system, wherein the request message comprises a request to invoke a target component available in the target environment and programmed in a language different from that of the application component; in response to the request, identify at least a service component associated with invoking the target component in the target environment; and run the service component to invoke the target component via a component interface.