7.7. Application Architecture
Because the application is still in its early phases, traffic can be accommodated on a single dual-Pentium-based, Windows NT server platform. However, modular design of the application will enable eTapestry to distribute functionality when patronage levels warrant. Although eTapestry does not yet use a fully distributed deployment, it uses key J2EE technologies.
7.7.1. Client Layer
Recognizing that many charitable organizations operate with older, donated machines, the front end was kept as simple—and thin—as possible. Accordingly, the user interface is entirely based on HTML and JavaScript, making the application extremely portable and resource-efficient. The application runs in any standard Web browser.
7.7.2. Web-Server Layer
eTapestry uses Microsoft Internet Information Server (IIS), which is bundled as part of Windows NT 4.0. The web server handles the incoming HTTP requests, which are handled through a standard Common Gateway Interface (CGI). SSL decryption is also handled at this tier to optimize internal communications between the Web server and application server.
7.7.3. Application-Server Layer
As mentioned earlier, all tiers of the application reside on a single server. For now, this means that application-server processes, such as load balancing and failover are not necessary.
Figure 7.1. The eTapestry Application's Current Architecture
The application layer contains numerous services, including the core application logic that provides the fundraising management functionality, plus supporting services, including directory and authentication, mail, SSL encryption/decryption, and XML processing. The processes are largely handled by servlets that are generated using the NewAtlanta ServletExec Servlet engine.
It also handles the all-important user authentication process. Users access the application through a standard login and password authentication procedure. This is preferable to alternatives, such as requiring users to obtain certificates from third parties, such as Verisign or Thawte. Although certificates in the long run might be more foolproof, requiring eTapestry users to install the necessary certificate management engines on their systems is not yet practical.