Metropolitan State University

ICS 325

Internet Application Development

Chapter 9 Approaches to Web Application Development (Shklar)

Common Application Functionality

· Accept user requests

· Interpret user requests

· Authenticate requestors

· Authorize requestors

· Access data

· Transform data

· Construct responses

· Transmit responses

Categories of Web Application Approaches

· Scripting or programmatic approaches (CGI, Java Servlets – code centric)

· Template approaches – uses a source object (template) with formatting structures and limited embedded constructs for programming (SSI – server side includes, Cold Fusion, WebMacro/Velocity)

· Hybrid approaches – combine scripting elements with template structures (PHP, ASP=>.NET, JSP)

· Frameworks

Web Application Frameworks

· Provide a consistent architecture for building and accessing request context elements that can be embedded within the web page (p. 246)

· Support state and session management and authentication

· Support for data access and transformation

· Separates content from presentation

· Patterns support frameworks

Buzzwords

· JSP – Java server pages (Sun)

· ASP – Active server pages (Microsoft)

· OLE - Object linking and embedding

· ODBC – Open database connectivity

· COM – Component Object Model

· IIS – Internet Information Server (Microsoft)

· LDAP – Lightweight Directory Access Protocol

Developers vs. Designers

· Separate content from presentation

· Different skill sets

· Some tools favor the developer; some favor the designer

Model-View-Controller (MVC) Pattern (see fig. 9.9)

· Data model should be usable by a variety of views

· Some controlling mechanism should be the glue that hooks up retrieved content with the presentation format

· Controller receives a user request

· Controller constructs the Model that fulfills this request

· Controller selects a view to present the results

· The View communicates with the model to determine its contents

· The View presents the contents to the user in the desired format

· The View acts as the interface for transmitting further requests from the user to the Controller

· Facilitates separation of content from presentation

· Allows applications to dynamically tailor the view based on user preference, device capabilities and business rules

· Controller – developer

· View – designer

Other Important Patterns (see pg. 263)

· Front Controller – a module acting as a centralized entry point into a Web application, managing request processing, performing authentication and authorization services, selecting the view

· Service-to-Worker and Dispatcher View – strategies for MVC applications where the front controller module defers processing to a dispatcher that is selected based on the request context

· Dispatcher View – dispatcher performs static processing to select the ultimate presentation view

· Service-to-Worker – dispatcher’s processing is more dynamic; logical task names are translated into concrete task modules; complex processing determines presentation view

· Intercepting Filter – allows for pluggable filters to be inserted into the request pipeline; performs pre and post processing

· Value List Handler – a mechanism for caching results from database queries, presenting discrete subsets of the results and providing iterative traversal through the sequence of subsets

· Data Access Object (DAO) – a centralized mechanism for abstracting and encapsulating access to complex data sources; DAO acts as an adapter allowing the external interface to remain the same even when the structure of the underlying data source remains the same

· Struts – uses MVC, Front Controller and Service-to-Worker patterns; allows the use of configurable application components

XML

· Meta data – data used to describe data

· Self-defining data structures

Web Application Development Approaches Compared

· See Table 91. on page 267