Virtual Classroom

Virtual Classroom Integrated Learning environment over internet Anshu Veda Prajakta Kalekar Shruti Mahambre The Client  This project has been sponsored by Intel IIT B point of contact Prof. Umesh Bellur  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.  Combines the benefits of HTTP tunneling and RMI over internet  RMI tunneling over HTTP 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:      Admin  Instructor Student Admin Instructor  Managing user accounts, course registration approval Login,Create / Modify course details, set Quizzes, assign grades Login, Register / Unregister for courses, take quizzes, view lectures in offline mode Open-Source and Freeware Support over Internet and Intranet  Student   Non-Functional Requirements   Technology Decisions Client Client •Integrated Environment Communication Protocol Internet •Cross firewall •Intranet and Internet support Server Server •Transaction •Persistence •Security •Caching Thin v/s Thick Client Feature Web Browser Vs Java Client Thin Client Different Browsers may require different plug-ins to support features such as Video streaming.  Look and feel varies from browser to browser.  Thick Client Gives integrated look and feel. The client executable, installable from web, can bundle all prerequisites.  Java Swing client gives same look and feel across all the platforms (as compared to web browser).  Speed Slow. Everything must wait for the server to process and transmit the next screen of information. Fast. Can instantly scroll since the client can cache and process data locally. Initial Architecture Diagram Swing Client Specs   Client- Swing Servlet ContainerTomcat3.2 DB ServerPostgres8.0 Servlet  Request Processor DB Manager Database Pros and Cons Pros  Simple  Simple and Intuitive. Uses HTTP over the internet and simple JDBC to communicate with the database server. As compared with J2EE server  Light  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 BMP Avoid unnecessary stores Done using dirty flags, but it requires more coding and is error-prone JDBC sql queries have to be code. CMP CMP engine handles this Coding Lesser Coding Architecture Diagram (The chosen approach) Session bean SessionBean EntityBean SessionBean SessionBean client SessionBean EntityBean Database EntityBean EntityBean 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 colocated 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 datarelated 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  Deployment Descriptor course vclassroom.course.ejb.CourseLocalHome vclassroom.course.ejb.CourseLocal vclassroom.course.ejb.CourseBean Container False 2.x course java.lang.Integer courseId courseId Deployment Descriptor ejbSelectprerequisites java.lang.Integer 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       After 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 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       Thank you !!!!