WebLogic Server Overview
Figure 1-1 shows a typical multi-tier WebLogic Server configuration. Clients include Web browsers and application clients. The WebLogic Server tier is usually a cluster of cooperating WebLogic Servers.
Figure 1-1. Typical BEA WebLogic Server Configuration
The pentagon is the WebLogic Server container, a complex concept encompassing a wide variety of services and facilities.
The Container-Component Model
The WebLogic Server platform (in Java parlance) can be thought of as a container that provides services to components of user applications. Components such as EJBs, JavaServer Pages (JSPs), and servlets reside in the WebLogic Server container and take advantage of the services provided by it.
In Figure 1-2, the WebLogic Server container (the large pentagon) encloses various J2EE services. Interconnections of services are depicted with lines and arrows. WebLogic Server management (via the WebLogic Server console) and security are shown as layers external to the container.
Figure 1-2. A Snapshot of the WebLogic Server Container
WebLogic Server Strengths: Component Support and Scalability
WebLogic Server's implementation of the J2EE server-based programming strategy centers on EJBs, which are at the heart of most enterprise-level Web applications. EJBs integrate data management, session management, and business logic, and coordinate among all the tiers of the application. For example, you use entity beans to represent data from the database. You use session beans to implement business logic that is either too complex or too sensitive to be managed with presentation logic, and you use message-driven beans to set up asynchronous data processing.
Within the WebLogic Server container, components are given connection and communications services, transactional support for multi-user operations, and the capability to replicate, or cluster, to provide better performance and scalability.
To the container and component framework, WebLogic Server added several important mechanisms for clustering to ensure high availability and scalability of distributed applications. A BEA WebLogic Server cluster is a group of WebLogic Servers that coordinate their actions to provide scalable, highly available services in a transparent manner. WebLogic Servers in a cluster can run on a heterogeneous mix of hardware and operating platforms: They interoperate through their Java-based, platform-independent APIs.
WebLogic Server clustering technologies transparently support replication, load balancing, and failover for both Web page generation (presentation logic) and EJB components (business logic).
Figure 1-3. Clustering
