NonStop Systems Introduction

The Application Server Environment
NonStop Systems Introduction— 527825-001
3-24
WebLogic Server and the J2EE Platform
WebLogic Server is Built Around Java Technology
WebLogic Server implements the Java 2 Platform, Enterprise Edition (J2EE) 1.3
platform specification. J2EE is a component-based, platform-independent architecture
that makes applications easy to write because business logic is organized into
reusable components. In addition, the J2EE server provides underlying services
essential for server applications. Because developers do not have to develop these
services on their own, they are free to concentrate on creating the business logic.
J2EE is based on Java technology. Java technology allows enterprise organizations to
easily create portable applications that can run on any platform that supports Java.
J2EE components are written in the widely-used and easily-learned Java programming
language. Java application developers who want to run their applications on NonStop
servers do not need to write code specific to the NonStop platform.
Developers can write J2EE applications that include the many services provided by the
J2EE specification. Among these services are:
•
Servlets and JavaServer Pages. These tools are used in the development of Web-
based applications. They extend the functionality of the WebLogic Server’s Web
server. NonStop Servlets for JavaServer Pages is the HP implementation of these
tools.
•
Enterprise JavaBeans (EJB). As described later in this section, EJB provides the
basic building blocks for J2EE server applications. NonStop EJB is the HP
implementation of Enterprise JavaBeans.
•
Java Message Service (JMS). This tool allows for asynchronous communications
between clients and servers and between distributed application components. In
asynchronous communication, a component can send a request, then continue
processing without waiting for a response.
Reliability and scalability are provided by the NonStop platform on which the Java
program runs, and taking advantage of these attributes does not require any code
changes or specialized programming skills. The inner workings of the NonStop
platform are invisible to Java developers. Existing Java language-based programs can
be easily adapted to the NonStop platform for a ZLE solution.
J2EE is Based on the Multi-Tiered Client-Server Architecture
The J2EE platform uses a multi-tiered distributed application model for enterprise
applications. Application logic is divided into components according to function. As
mentioned earlier in the section, J2EE applications fit well into the three-tiered
arrangement used by WebLogic Server. Figure 3-16 on page 3-25 shows the parts of a
J2EE application.