Corporate.Net Web Middleware Glue Binds Web Apps Visigenic VisiBroker If you've embraced object-oriented programming and want to create complex, Web-based applications for large networks, VisiBroker could be just the ticket. Working with VisiBroker for Java is easy and painless, both from the programmer's and network administrator's point of view. The Interface Definition Language (IDL)-to-Java code generator quickly built skeleton Java code for us, which we used as the framework for a serious application development effort. Visigenic's paradigm for distributed computing is ORB-based and well-suited for applications whose development follows object-oriented programming (OOP) standards. VisiBroker for Java and VisiBroker for C++ are CORBA 2.0 request brokers that use the Internet Inter-ORB Protocol (IIOP) for interprocess co mmunication between network nodes. The IIOP within the C++ product is a compiled, native-code (C++) implementation, while the IIOP of VisiBroker for Java is written entirely in Java. VisiBroker for Java helped our development efforts with its IDL-to-Java code generator, multith readed architecture and support for both client-side and server-side Java. We used the product's design-time portion to convert object interfaces (rendered in IDL) into skeleton Java programs. These were immediately ready for the inclusion of business logic. The run-time portion managed our communications between distributed applets and other objects. We also employed the IIOP GateKeeper, which Visigenic wrote in pure Java, to play the role of communications switchboard for applet-to-object-server linkages. We noted the GateKeeper can act as an HTTP server for testing purposes. But because it's written in Java and interpreted at run-time, it isn't fast enough to handle a production environment. We also noted that both the Java and C++ versions of VisiBroker used an agent-based architecture, performed automatic configuration--and reconfiguration as the network changes--balanced workloads among active server objects across the network, and offered what Visigenic terms "smart binding." In tests of these products' agent-based environment, multiple instances of VisiBroker smart agents tracked which network server objects were running and which were down. When we deliberately made a server object fall off the network, or go down, the agents reconfigured by telling the clients, via an IIOP dynamic reregistration process, to use other available server objects. These same agents performed load-balancing rather intelligently by keeping track of transaction activity and response times. The smart agent technology stood up against our deliberate disruption of the server and network infrastructure. VisiBroker isn't a true TP monitor middleware product and doesn't include transaction integrity and database access features. But since Visigeni c has a great deal of experience with database connectivity, we'd like to see the company offer additional CORBA services with the next version of its ORB to help programmers manage transactions and server objects. The smart binding feature did a good job of hiding the details of n etwork communications from us. In every case, VisiBroker chose the most appropriate communications mechanism (transport layer protocol) when we shared data across the network among various application components. VisiBroker for C++ gave us an IDL-to-C++ compiler, static and dynamic invocation interfaces, an object-activation daemon, and object administration and ORB monitoring tools. We discovered the IDL compiler is a full CORBA implementation of IDL and complies with CORBA's C++ Mapping specification. The object-activation daemon conserved server resources by making sure only the objects currently in use (or frequently needed) were running and available. VisiBroker for C++ runs on Sun Microsystems' SunOS 4.x, SunSoft 's Solaris 2.3, Digital Equipment Corp.'s Unix, HP-UX, AIX, Windows95 and Windows NT. The NT version requires NT Server 3.51 or later, a 486 or faster processor, 16 MB of RAM and 15 MB of free disk space.

For a look at the Transparency of Middleware Internet Rx by Chris Lewis The Dawining of the Age of Java Management by Bruce Boardman Updated May 12, 1997