NonStop Servlets for JSP System Administrator's Guide

Overview and Architecture

NonStop Servlets for JavaServer Pages (NSJSP) System Administrator’s Guide—525644-001

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Java 2 Enterprise Edition (J2EE) Overview

J2EE enables the use of dynamic applications to communicate over HTTP with client

browsers, specifically web containers, servlets, JSP, Java classes, and deployment

descriptors.

The iTP WebServer implementation of Servlets and JSP is a key component for J2EE

compliance. The iTP WebServer implementation enables support for Java-based

NonStop products.

For an overview of all the other components of a complete J2EE environment, consult

the Sun Microsystems J2EE website.

The J2EE architecture has two types of client; web clients and application clients.

Application clients belong to the client-server model where the “fat” client provides not

only the GUI, but also most of the application logic. Web clients, on the other hand,

belong to a newer three-tier model where the “thin” client (typically a browser) supplies

the GUI, and a middleware layer, on a Webserver, provides the application logic

between the GUI and the database. The middleware layer itself is now typically based

on reusable components designed in a Model-View-Controller architecture. For an

introduction to this concept, see Model-View-Controller Designs on page 1-7.

The web client model typically uses Hypertext Transfer Protocol (HTTP) to provide a

request-response relationship between the browser and the application logic. The

client Resource Locator (URL) — for example www.company.com/index.html —

consists of the domain name — www.company.com — and the Universal Resource

Identifier (URI), the name of the resource, in this case index.html. The URI provides

the context path that is used to locate servlets (see Map Requests to Applications and

Servlets on page 3-15).

Initially, HTTP resources were static pages of text or graphics, the same resource

being served to each client request, but now the emphasis is on building and using

dynamic resources where the same resource can be dynamically modified for each

different client request. An example could be a mailbox, where the structure and

function is the same, but the content is clearly different for each user.

Dynamic content was initially supplied by CGI, but now the more powerful and flexible

Servlet API and JSP programs are used to provide logic for the new web applications.

This subsection summarizes the following topics:

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The Web Container on page 1-3

•

JavaServer Pages (JSP) on page 1-4

•

The Web Application on page 1-5

•

The WEB-INF Subdirectory on page 1-5

•

The Deployment Descriptor on page 1-5

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Web Archive (WAR) Files on page 1-6