Sun Java Enterprise System 2005Q4 Technical Overview

Infrastructure Service Levels

In designing a distributed software system, whether it consists mostly of custom-developed components or of out-of-the-box Java ES components, you need to incorporate a number of infrastructure services. These services operate at many levels.

The infrastructure service dependency dimension of solution architecture is illustrated in Figure 2–2. The levels shown in this figure are an expanded view of the infrastructure service layer of Figure 1–1.

The hierarchy of services in Figure 2–2 and the dependencies between them constitute an important dimension of a solution’s logical architecture. These infrastructure services provide the conceptual basis for understanding the role of Java ES system service components (see System Service Components).

In general, the services shown in Figure 2–2 divide into three broad groupings: low-level platform services, high-level application services, and a group of middleware services, named for their location between the other two groupings.

Figure 2–2 Dimension 1: Infrastructure Service Levels

Diagram showing distributed service infrastructure levels from
lowest level operating system platform services to highest level integration services.

The following paragraphs describe the different infrastructure service levels and refer to Java programming language artifacts, where relevant. The service levels are described from lowest to highest, as shown in Figure 2–2:

The service levels shown in Figure 2–2 reflect a general dependence of the various infrastructure services on one another, from the lowest-level operating system services to the highest-level application and integration services. Each service generally depends on services below it and supports services above it.

Figure 2–2, however, does not represent a strict layering of infrastructure services. Higher-level services can directly interact with lower-level services without depending on intermediate levels. For example, some runtime services might depend directly on platform services without requiring any of the service levels in between. In addition, other service levels, such as a monitoring or management service, might also be included in this conceptual illustration.