Deborah Hess
Vendors of object development products are using the Web as a transport and communications mechanism for distributed objects and as a front end (via Java-based applets and browsers) for object applications. This comes as an outgrowth of the Object Management Group's (OMG) Common Object Request Broker Architecture (CORBA) version 2.0, which provides a vehicle for communications between object request brokers (ORBs) developed by different vendors and between objects whose transactions the ORBs manage.
The new vehicle, the General Inter-ORB Protocol (GIOP), specifies message formats and data representation across any transport protocol. A second specification, the Inter-ORB Implementation Protocol (IIOP), provides preconfigured interoperability for ORBs running over TCP/IP, thus allowing the Inter
net to act as a backbone ORB that's accessible to other ORBs. The produc
ts below are part of the first round of object applications to use Internet technology. Expect additional implementations as improved object and Web standards appear over the next year.
BlackWidow, from Visigenic ((415) 967-6169;
http://www.visigenic.com
).
The BlackWidow ORB creates client- and server-based object applications that Java-enabled browsers can access. It's well suited for distributed applications because it provides two-way access between Java applets and objects on remote systems.
With BlackWidow, developers can convert interface definition language (IDL) interfaces to Java on clients and servers, create Java applets, and provide bidirectional access between Java
applets and objects arranged by other ORBs. Since BlackWidow clients can directly invoke these objects, developers avoid the tedium of creating Common Gateway Interface (CGI) scripts for every invocation on a server.
BlackWidow's development component, an automatic IDL-to-Java code generator, converts object interfaces into both client- and server-side Java code; developers create distributed Java applets by adding application logic. The run-time component manages object location, connection, and communication, and it can access any Java-compliant Web browser.
OrbixWeb, from Iona ((617) 679-0900;
http://www.iona.com
).
OrbixWeb is part of the Orbix family of CORBA-compliant ORBs. OrbixWeb lets Java applets on a host use distributed objects managed by any CORBA 2.0 ORB. Unlike BlackWidow,
OrbixWeb provides client-side development only, and it requires a separate Orbix server.
OrbixWeb includes a mapping between Java and the IDL, which associates IDL basic, template, and constructed data types with the appropriate Java constructs. Each IDL interface provides two Java mappings: one to Java interfaces for inheritance purposes, and the other to Java classes for implementation. Although limited to the client, OrbixWeb can access a variety of technologies and platforms through other Orbix products.
Visual Wave/GemStone Internet Application Server, from GemStone and ParcPlace-Digitalk (GemStone, (503) 629-8383;
http://www.gemstone.com
).
Applications-server (and former object-database) vendor GemStone and Smalltalk provider PPD together offer a large-scale Internet applicatio
ns server. The Visual Wave/GemStone Internet Application Server (IAS) can deploy transaction-based Smalltalk applications supporting thousands of concurrent users via TCP/IP. IAS provides a three-tiered architecture for Internet applications. PPD's VisualWave Server functions as the back-end Internet server; its Visual Wave development environment creates client front ends with hooks to popular browsers. The GemStone 4.1 object application forms the middle tier.
Visual Wave servers can be clustered, and the Visual Wave development environment automatically generates client-side HTML and CGI scripts directly from Smalltalk. It also lets developers update Web applications on the fly. GemStone IAS provides scalability, transaction integrity, and gateways to relational databases. It also lets developers use object technology instead of stored procedures for working with distributed databases.
Deborah Hess is a senior analyst at DataPro Information Services (Delran, NJ). For more information
, call (800) 328-2776 or (609) 764-0100.
CORBA, Java and the Web
