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ADVANCED WEB DEVELOPMENT CHAPTER 1 - INTRODUCTION TO JAVA WEB TECHNOLOGY…
ADVANCED WEB DEVELOPMENT CHAPTER 1 - INTRODUCTION TO JAVA WEB TECHNOLOGY
Component Web Application
Three Tier (Web Server
Browser handles presentation logic
Browser talks Web server via HTTP protocol
Multi-Tier
Separation between presentation logic, business logic and database access logic
More flexible when making changes, i.e. Presentation logic can change without affecting the other tiers
Three Tier (Remote Object based)
Business logic and data model captured in objects
Object Models used: CORBA, RMI, DCOM
Presentation logic
In software development, presentation logic is concerned with how business objects are displayed to users of the software, e.g. the choice between a pop-up screen and a drop-down menu
One major rationale behind "effective separation" is the need for maximum flexibility in the code and resources dedicated to the presentation logic
Three Tier (RCP- Based)
Thinner Client: Business & data model separated from presentation
Middle tier server is now required to handle system services
Data Access Logic
Provides an abstract interface to some type of database or other persistence mechanism
Two Tier
Fat clients talking to back end database
Presentation, Business logic and Data Model processing logic in client application.
Business logic
Programming that manages communication between an end user interface and a database. The main components of business logic are business rules and workflows
A business rule describes a specific procedure; a workflow consists of the tasks, procedural steps, required input and output information, and tools needed for each step of that procedure
Single Tier (Mainframe-based)
Centralized model
Presentation, business logic, and data access are intertwibed in one monolithic mainframe application
Dumb terminals are directly connected to mainframe
Java EE Architecture
Business logic is organized into reusable component
Provides configurable services
Application components within the same Java EE application can behave differently based on where they are deployed
Easy to write
Platform-independent
Java EE server provides underlying services in the form of a container for every component type
Component-based
Technologies in Java EE
HTML for Client Side
Client-end scripts embedded in website's HTML markup code, housed on server in a language that is compatible with, or compiled to communicate with, the browser
All websites run on three components
Database
Client
Server
Browser downloads the code, then apart from the server, processes it
Servlets / JSP for Server Side
Receive and respond to requests from Web clients, usually across HTTP
Extend functionality of a HTTP server
Can be generated automatically from JSP
Difference
Servlets
Embed HTML inside Java code
JSP (Java Server Page)
Embed Java code in HTML
Small Java program that runs within a Web server
Java Applet
Do not have access to all the resources in user's computer
They are "Sandboxed" - To mitigate system failures or software vulnerablilities from spreading
Java program that is called from a Web page and downloaded from a server
Enterprise Java Beans (EJB)
Architecture for setting up program components, written in Java programming language, that run in a server parts of a computer network
Has the advantage of being able to control change at server rather than having to update each individual computer
For server side business presentation
Java Application
Java Virtual Machine interprets instructions, and running in its native environment
Have full access to all the resources in the computer
Java program that runs stand-alone in a client or server
Servelet API
Receives client request
Extract some information the request
An extension to Java that provides a programming interface(API) for implementing server-side programs written in Java(Java servlets)