Dr. Dobb's Journal - December 2008 - (Page 36)

d11haas_p5db 10/13/08 7:25 AM Page 36 Core Technology A REMOTE JAVA RMI REGISTRY Figure 1: Standard Java RMI system architecture with local RMI registries in FMC notation (www.fmc-modeling.org). (1) RMI server object (re)binds itself to the local RMI registry running on the same machine—(re)binding to a remote RMI registry is prohibited (AccessException). (2) RMI clients lookup the specific RMI registry to get a remote reference (a client stub), to the server object. (3) RMI client invokes methods on the remote server object via the client stub. Figure 2: Extended Java RMI system architecture with a remote RMI registry in FMC notation (www.fmcmodeling.org). (1) An RMI server object (re)binds to the remote RMI registry. The bindings in the remote RMI registry are stored persistently—to garbage collect invalid bindings, the remote RMI registry periodically pings the server objects. (2) RMI clients lookup the remote RMI registry to get the remote reference to the server object. (3) Remote method invocation is done as usual. communication protocol, RMI registries must be publicly accessible, whereas the RMI server objects (the peers) can reside behind NAT borders. Independent of that project, a remote RMI registry provides added value to Java RMI because it enables new distribution models. For example, instead of several RMI registries collocated with the distributed server objects, a single central RMI registry can be run. This simplifies the operation and maintenance of a Java RMI-based distributed system, and provides transparency of the server object locations, which in turn allows for transparent object migration. Our remote Java RMI registry was designed to meet the following goals: • Complete transparency to RMI servers and clients. Our primary goal was to provide complete transparency in the sense that RMI servers and RMI clients can use our custom remote registry instead of the standard registry without any change to their code. To meet this objective, the custom registry must not only provide the standard Registry interface, but RMI clients and servers must be able to use the getRegistry method of the JRE built-in class LocateRegistry to obtain a reference to our custom registry. While other remote registries have been described, we are not aware of one that can be accessed through the LocateRegistry.getRegistry method. • Simple trust model without need for authentication and authorization. Authentication and authorization is not only a complex issue, but its use would also require extensions of the registry interface and thus negate the transparency mentioned earlier. We thus opted for the following simple, straightforward extension of the trust model of the reference implementation: When a name is bound, we store the sender IP address together with the mapping. Only this sender may rebind or unbind the same name. 36 Dr. Dobb’s Journal l www.ddj.com l December 2008 http://www.fmc-modeling.org http://www.fmc-modeling.org http://www.imagix.com http://www.ddj.com

Table of Contents Feed for the Digital Edition of Dr. Dobb's Journal - December 2008

Dr. Dobb's Journal - December 2008 Contents Friday Night Fish Fry Alia Vox Developer Diaries Conversations The Man Who Sold the Sky Performance on Rails LINQ-to-SQL and T-SQL A Remote Java RMI Registry Beyond B-Trees File Descriptors and Multithreaded Programs Effective Concurrency The Agile Edge Swaine's Flames

Dr. Dobb's Journal - December 2008

For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.