An Example of Application Servers and Web Services
In this example, the retail clients and in-house clients of a financial company use the portfolio management portal to monitor their investments. The front-end of the portal is built using Microsoft technology (Active Server Pages (ASPs), Internet Information Services (IIS) Web Server, and VB Script; note that although these are not .NET products, the approach is essentially the same). One of the features provided within the portal application is quote information. Using this feature, the clients can retrieve real-time quotation for any stock. When the client requests a quote for any stock, the request is sent from the browser to the Web Server. The quote service is provided as a Web Service by a middleware application within the company to multiple clients, with our portfolio management portal being just one of those clients. Another client, as shown in the figure, is a VB application. The information about Web Services offered by this middleware application is obtained from the private internal UDDI registry and invoked over the intranet. The implementation of the business methods exposed by the Web Service is provided by EJBs contained in another Application server. This is a typical example of cross-platform application server integration using Web Services. The binding information for frequently used Web Services, such as those for requesting quotes, can be cached by the client application, to avoid the resource intensive and time consuming dynamic binding. In this example, Web Services loosely integrates the portfolio management (Microsoft technology-based) application with the (J2EE-based) middleware application that interfaces with the Mainframe to receive the quote.
The sequence of steps is as follows:
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© Lynne Grewe |