2.J2EE_Overview.ppt

Sapana Mehta (CS-6V81)
Overview Of J2EE & JBoss
Sapana Mehta

Past History
 Initially two tier architecture (client
server applications)
 Client is responsible for data access
applying business logic and
presentation of data
 Only service provided by Server was
that of database server.

Two Tier Application
Architecture
Client Server

Two Tier Application
Architecture
 Drawbacks
- Easy to deploy but difficult to enchance
or upgrade.
- It makes reuse of business and
presentation logic difficult
- Not scalable and not suited for internet

Java 2 Platform Enterprise
Edition(J2EE)
J2EE is an architecture for implementing
enterprise class applications using Java
and Internet Technology
- Solves problems of two tier architecture

J2EE
 To develop n tier application
 It supports the development of a
variety of application types
 small client server systems
 Systems running on Intranets
 Systems on large scale internet e-
commerce site

J2EE Features
 Component based model
 Container provided services
 Highly Scaleable
 Simplified Architecture
 Flexible security model

Java: Foundation for J2EE
 J2EE is an application of java
 Write once and deploy the code into
any platform

J2EE Components & Services
 Primary technologies
- Servlets
- JavaServer Pages (JSP)
- Enterprise JavaBeans (EJB)
 Standard services & supporting technologies
- Java database connectivity(JDBC) data access API
- Remote Method Invocations (RMI)
- Extensible Markup Languages(XML)
- JavaIDL
- JavaMail

J2EE Tiers
 Client Presentation
 HTML or Java applets deployed in Browser
 XML documentations transmitted through
HTTP
 Java clients running in Client Java Virtual
Machine (JVM)
• Presentation Logic
 Servlets or JavaServer Pages running in
web server
• Application Logic
 Enterprise JavaBeans running in Server

J2EE Application Model
 Browser is able to process HTML and
applets pages.
 It forwards requests to the web server,
which has JSPs and Servlets
 Servlets and JSPs may access EJB
server.
 Java Standalone runs on java client,
which access EJB server using RMI.

J2EE Application Model

Enterprise Java Beans (EJBs)
 Enterprise Java beans architecture is a component
model for development and deployment of
distributed business application.
 Entity Beans
 Represent persistent business Entity
 Persisted in storage system ( usually Database)
 Might contain Application logic intrinsic to entity
• Session Beans
 Perform work for individual clients on the server
 Encapsulate complex business logic
 Can coordinate transactional work on multiple entity
beans

States and Persistence
 Session beans can be
 Stateless- belong to client for duration of a
method call
 Stateful- belong to client for duration of client
conversation
 Entity beans can have
 Bean-managed persistence- The developer writes
SQL code to retrieve,store and update database
 Container managed persistence- The developer
provide database mapping information that allows
the container to manage persistence

Example of EJB Application
 It consists of number of clients accessing
session beans and entity beans
 Each Session bean provides specialized
processing on behalf of client
e.g. Travel Agent session bean makes travel
reservations while Flight Scheduler bean
schedules planes to fly on various routes.
 Each Entity Bean represent different type of
business entity.
e.g.Passengers, seats, planes, flights are entity
beans

Example EJB Application

Overview of Servlets
 Are container managed web components
 Replace Common Gateway Interface(CGI) or
Active Server Pages (ASP)
 Generate dynamic response to requests from
web based clients
 Synchronize multiple concurrent client
request
 Serve as client proxies

Servlet Operation
 Server is Java program that runs as
separate thread inside servlet container.
 Servlet container is part of web server
 It interact with web client using
response request paradigm

JavaServer Pages (JSP)
 Text based documents describe how to
process a request and create a
response
 Contains HTML or XML and other JSP
elements defined by JSP specification.
 Are Installed on web server
 are web components that sits on top of
java servlet mode.

JSP Advantages
 Performance
 Runtime characteristics of servlets
 Automatic recompilation of modified pages
 Server side processing
 Programming
 Emphasize use of reusable components
 Write Once , Run Anywhere properties
 Extensible through custom tag libraries
 Provides front end access mechanism to
EJBs

Parts of JSP Pages
Directive
<%@ pageimport=“java.util.”, MVCApp.Cart, MVCApp.CartItem” %>
Declaration
<%! Iterator it = null; CartItem ci = null; Vector cpi = null;%>
Raw HTML
<html><head><title>Shopping Cart</title></head></html>
Action
<jsp:usebean id =“Cart” scope = “session” class = “MVCApp.Cart”/>
Scriplets
%
Cpi = cart.getCartItems ( );
it = cpi.iterator();
While (it.hasNext()){ci= (Cart Item)it.next();
%>

Parts of JSP Pages
 Expression
<td<% = ci.getTitle() %></td>
<td align =“right”><%=ci.getQuantity()%></td>
 Implicit Objects
<% string action = request.getParameter(“action”) ; %>

JBoss- J2EE Product
FIND OUT MORE ABOUT
TODAY’S MOST SUCCESSFUL OPEN
SOURCE- DEVELOPED APPLICATION
SERVER

What is JBoss
 Created in 1999, JBoss is the product of an
OpenSource developer community dedicated
to developing the best J2EE-compliant
application server in the market
 With 1000 developers worldwide and a
steadily growing number of downloads per
month, reaching 72,000 for October ’01 (per
independent www.sourceforge.net), JBoss is
arguably the most downloaded application
server in the world today
 Distributed under an LGPL license, JBoss is
absolutely FREE for use. No cost. Period.

What is Application Server
 Application servers enable the development
of multi-tiered distributed applications.
They are also called “middleware”
 An application server acts as the interface
between the database(s), the web servers
and the client browsers

JBoss- Application Server

Conclusion
“First they ignore you
Then they laugh at you
Then they fight you
Then you win”
-- Mahatma Gandhi

2.J2EE_Overview.ppt

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