NonStop Systems Introduction

The Application Server Environment
NonStop Systems Introduction— 527825-001
3-26
WebLogic Server and the J2EE Platform
J2EE Applications Are Composed of Enterprise Beans
A key component in the J2EE architecture is the enterprise bean.
An enterprise bean is a module of Java code that contains business logic and is written
according to the Sun Microsystems Enterprise JavaBean (EJB) specification. You can
think of enterprise beans as “building blocks” that are assembled into applications that
meet the needs of a particular business domain such as banking, retail, or finance.
Programmers that write bean code are known as “bean providers”. enterprise beans
constitute the middle tier (the business logic) of the distributed three-tiered
architecture.
Enterprise beans are highly portable; individual beans can be easily moved from one
platform to another. And because EJB is in such widespread use throughout the
industry, third-party vendors offer precoded beans that can be quickly and easily
assembled into complete applications. Another benefit is that EJB integrates easily
with other application server platforms (for example, CORBA clients can invoke
enterprise beans).
Figure 3-17 on page 3-26 illustrates the basic EJB architecture.
As Figure 3-17 on page 3-26 shows, the basic EJB architecture consists of the
enterprise beans themselves, clients that invoke the Beans, a bean container, and the
EJB server in which the beans run. The EJB server in this case is WebLogic Server.
Figure 3-17. EJB Architecture
NonStop server
WebLogic server
Servlets
or JSP
Web container EJB container
Clients
Web browser
Java program
Enterprise
beans
Servlets or
JSP
Enterprise
beans
Database
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