Special Edition Using Enterprise JavaBeans™ 2.0

N-Tiered Architectures

Another classification that architectures fall into is the number of different layers, or tiers, the architecture has. A tier is a grouping of software and possibly hardware, components, and services. This grouping can be both logical and physical. The purpose of using tiers is to enable the software components and services to be distributed across multiple computers for scalability and security. For example, as you’ll see in Chapter 19, “Building a Presentation Tier for EJB,” the Web server components and services are sometimes distributed in a different tier than the application services. This adds security to the application because more of the application can be located deeper in a protected network. The three most ...