Presented by:
Anshu Veda
Prajakta Kalekar
Shruti Mahambre

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Virtual Classroom
Integrated Learning environment over internet
Problem Definition
This project aims at putting together an integrated e-Learning environment for a university student.
This will also be used by distance education programs offered by institutes, in order to enable students to avail of the academic facilities from any computer connected to the internet.
Basic terminology
RMI (Remote Method Invocation)
Server application creates remote objects, makes references to them available and allows clients to invoke methods on these remote objects.
 RMI tunneling over HTTP
Combines the benefits of HTTP tunneling and RMI over internet
 EJB
 Session Beans (verb)
Model business processes. They represent actions
 Entity Beans (noun)
Model Business data – They are data object, java objects that cache database information
 EJB Container
 House enterprise beans and make them available for clients to invoke remotely
 Provide an environment in which enterprise beans can run
 “Invisible middlemen”
EJB Architecture
Basic Terminology
 CMP – Container Managed Persistence
 EJB container takes care of making sure the entity bean object stays around.
 BMP – Bean Managed Persistence
 You as the bean programmer can take over the responsibility of managing the "persistence" of the data -- of where the data stays when the server is not running or when the bean is not in memory.
Requirement Specs
 The system will be having 3 roles:
 Instructor
 Student
 Admin
 Admin
 Managing user accounts, course registration approval
 Instructor
 Login,Create / Modify course details, set Quizzes, assign grades
 Student
 Login, Register / Unregister for courses, take quizzes, view lectures in offline mode
 Non-Functional Requirements
 Open-Source and Freeware
 Support over Internet and Intranet
Technology Decisions
Thin v/s Thick Client
 Initial Architecture Diagram
Specs
 Client- Swing
 Servlet Container-Tomcat3.2
 DB Server-Postgres8.0
 Pros and Cons
Pros
 Simple
 Simple and Intuitive. Uses HTTP over the internet and simple JDBC to communicate with the database server.
 Light
 As compared with J2EE server
Cons
 Plain Http protocol – No type safety
 No caching Support
 No Transaction Management Support.
 Absence of Distributed Objects.
 WebServices ???
RMI offers an order of magnitude better performance than other alternatives, being at least 8.5 times faster than Web Services
 HTTP-to-servlet is more than 4 times slower than web services.
 Reference: “Java RMI, RMI Tunneling and Web Services Comparison and Performance Analysis” - Matjaz B. Juric, Bostjan Kezmah, Marjan Hericko, Ivan Rozman, Ivan Vezocnik
Why EJBs?
 Container inherently provides features such as
 Security
 Transaction Management
 Persistence
 Distributed Object Support that goes well with RMI.
CMP vs BMP
 Architecture Diagram
(The chosen approach)
Session Facade
 Performance
 An Entity bean is equivalent to a row in the database. If the Entity beans were to be accessed directly, a network call would result for each row access.
 On the other hand, a Session bean is equivalent to a stored procedure. Accessing a session bean that is co-located with an entity bean emulates accessing a row through a stored procedure.
Session Facade
 Reusability
 The session bean layer is powerful because it externalizes all business logic from the entity beans. This means the entity beans contain data and data-related logic only.
 This promotes high re-use of entity beans.
 Data abstraction layer
 The session bean layer is a facade. The particular way the session bean persists (via JDBC directly or via entity beans) is an implementation detail of the session bean. The decision about whether to use JDBC or entity beans can be deferred until a later date.
E-R Diagram
 Object Model
 Collaboration Diagram - Login
 Collaboration Diagram - Registration
 Sequence Diagram - Registration
 Collaboration Diagram – Set Quiz
 Class Diagram
 Class Diagram (old & new)
 Lessons learnt / Challenges faced
 1. Familiarity with J2EE
 Studying EJB Architecture (session bean, entity bean concepts)
 BMP vs CMP
 Concept of CMR
 Configuring JBoss 4.0
 Configuring Postgres 8.0 on JBoss
 Serial – Primary Key
 Writing Deployment Descriptors
 Challenge
 Trying to synchronize the Intel deadlines with the syslab deadlines throughout this course J
Deployment Descriptor
<entity>
<ejb-name>course</ejb-name>
<local-home>vclassroom.course.ejb.CourseLocalHome</local-home>
<local>vclassroom.course.ejb.CourseLocal</local>
<ejb-class>vclassroom.course.ejb.CourseBean</ejb-class>
<persistence-type>Container</persistence-type>
<reentrant>False</reentrant>
<cmp-version>2.x</cmp-version>
<abstract-schema-name>course</abstract-schema-name>
<prim-key-class>java.lang.Integer</prim-key-class>
<primkey-field>courseId</primkey-field>
<cmp-field>
<field-name>courseId</field-name>
</cmp-field>
Deployment Descriptor
<query>
<query-method>
<method-name>ejbSelectprerequisites</method-name>
<method-params>
<method-param>java.lang.Integer</method-param>
</method-params>
</query-method>
<ejb-ql><![CDATA[SELECT OBJECT(p) FROM course as c, IN(c.prereqCourses) p
WHERE c.courseId = ?1]]>
</ejb-ql>
</query>
</entity>
Technologies / Tools / Methodologies Learnt
J2EE Architecture
 Enterprise Java Beans
 JBoss 4.0
 Postgres 8.0
 EJB-QL
 Swing (work in progress)
 Patterns – Session Façade, Recursive Meta pattern, Chain of responsibility
 The Timeline
Before MidSem
 Overview of the system requirements from Intel
 Requirement Specification Document – prepared and presented to Intel
 Architecture + Design Documentation
 Prototype : Demo – with the old architecture – Login, Registration, Quiz
 Deliverable – Client + Server implementation of modules
After Midsem
 Change in architecture – Protocol + Server Side
 Learning Curve for new technology – EJBs, J2EE architecture
 Technology survey - Exploring options like JDO, Web Services
 Configurations – JBoss 4.0, Postgres 8.0
 Design of new architecture – Presentation to Intel
 Detailed Design specification documentation
 Deliverable – Server Side coding + documentation – Login, Registration, Quiz