Java™ Application Development on Linux - Dator

5.8 Introducing RMI137Here you see the class being run, and, sure enough, it displays our username.We then run su to become root and (after setting that library path) runit again—and, sure enough, it tells us we are “root.”We’ll talk more about JNI later in the book, but now you know enoughto be dangerous.5.8INTRODUCING RMIRemote Method Invocation (RMI) is a system for distributing application codeover multiple hosts. It is a small part of multitier computing. Much of this bookwill be devoted to the how’s and why’s of multitier client/server computing.Here we are concerned only with the SDK tool rmic, the RMI compiler.5.8.1 A Brief Introduction to RMIRemote Method Invocation is a basic client-server model for invoking Javamethods over a network.5.8.1.1 History and BackgroundOne of the most common problems in computing is how best to make an applicationavailable to the largest number of users at the least cost. To this endwe have seen the development of “timeshare” systems with dumb terminals allover the place. We have seen the evolution of distributed GUI systems with XWindows and its network display system, and with tools like VNC (VirtualNetwork Console). 16 We have seen the emergence of the PC, providingautonomous computing at each worker’s desktop. And finally we have seen thedesktop turning slowly back into a terminal (albeit a prettier one) with theemergence of client-server computing.What seems to have emerged from this progression is two major kinds ofsoftware systems. One is the PC and associated hardware and software. <strong>Development</strong>shere have dramatically increased the power and productivity of individualwork. The PC revolution was indeed a real change throughout the worldof business and technology. But even with this, there are a host of applicationsand business functions that require a collection of data and resources to beavailable to multiple workers at the same time. This is the second major kind16. http://www.realvnc.com/