Session 2 Tp2

ACCP2005/EJB 2.0/Session 2/1 of 25

Architectural Overview of EJB

Session 2

ACCP 2005/EJB 2.0/Session 2/2 of 25

Session Objectives

Explain the stages in Business Development Recognize the parties involved in the deployment

of Enterprise JavaBeans Define Enterprise JavaBeans Explain the classification of Enterprise JavaBeans Discuss the two types of session beans and entity

beans Explain the responsibility of the EJB Server and

Container


Review of Session 1

In session 1, we did the following: Discussed Component Architecture Described Distributed Object Architecture Discussed RMI Explained RMI-IIOP Discussed the Java Naming and Directory

Interface


Stages in Developing Business Solutions

Grouping of resuable modulesby vendors

Running of these EJB components on multi-tier applications

Combining the components into a workflow

Deploying the whole system over multiple systems across the network

Application Servers are provided by middleware vendors. These servers are needed to run the components


Parties Involved in EJB Deployment

Bean Provider

Parties in EJBDeployment

Container Provider The Deployer

Server ProviderApplication Assembler

System Administrator

Provides reusable components

Provides low-level execution environment

Supplies Application server logic

Puts together components and applications

Deploys prewritten components

Monitors functioning

EJBCont/

Server


Logical EJB Architecture

Client

HomeInterface

Remote Interface

EJB

ServerHome Object

EJB Object

JDBCDatabase


The EJB Container

THE SERVER

THE EJB CONTAINER

THE CLIENTOutside World

The container which resides insides the server acts as a BUFFER between the the beans and the outside world.

Connects clients to the Beans

Managing Life-cycle of a Bean


The EJB Server

Server

Container 1 Container 2

Client

Process and Thread Management

Responsibilities

System Resource Management

Database Connection


The Application Assembler and EJB Deployer

Assembled application

EJB Deployer

Operational Environments

Application

Assembler

Server Side

Client Side


Services provided by the Container and Server

Container/Server

Transaction supportSupport for management

of multiple instances

Persistence supportSecurity Support


Security Support

EJB The Access Control List

Functionality 1

Functionality 2

Functionality 3The ACL comprises the list of persons who are allowed to access particular sections of functionality.


Persistent Support

Persistence can be defined as saving the state of an object to a constant storage.

The state of the object is maintained

in this constant storage


Support for Management of Multiple Instances

InstancePassivation

Instance pooling

In order to perform timely servicing to the client the container performs a variety of tasks.

Server Tasks

Database connection pooling


Enterprise Beans

The Enterprise Java Bean is a server-side component that is employed on a distributed multi-tier environment.

Enterprise Bean

Session Bean Entity Bean

Stateful Bean

Stateless Bean BMP CMP

Message Driven Beans


Features of an EJB Container

Resource Managementand Life Cycle

Management of a Bean

Features

State Management

Transactions Security

Persistence

Remote Accessibility and location transparency


Resource Management and Life Cycle of a bean Management of resources enhances the

scalability of a multi-tier architecture. The container provides resource-

management services for resources such as: Threads Socket Connections Database Connections


State Management

Fills up

Applicationin a sitePage 1

Submits the form Applicationin a sitePage 2

User takes timeas he reads the contents in the page

Client

Container is used for another process while user takes time

to read


Transactions

Operation2

Operation1

Operation3

Executed as one unit of work

Multiple usersuse the same data


Transactions-Two phase commit protocol

Transaction Coordinator

Database 1

Database 3

Database 2

Prepare Phase

Prepare message

Commit Phase

Commit/Rollback Transaction Request

All databases issue commit request

Commit/Rollback Transaction Request

Records results of transaction


Remote Accessibility

Bean Bean Bean

Deployed across multiple tiers

Bean Bean Bean

Networked after deployment

Not-Networked


Location Transparency

Component

Component

Clients do not know where the components are, and whether these components are local or remote


Specialized Containers

Integration to mainframe systems Stateful recovery Distributed transactions Database persistence services that are complex Integrated XML services Dynamic redeployment of components in a

system that is running


Summary - 1

Four stages are followed while developing business solutions:

* Vendor grouping of product into modules * Running of the EJB component on multi-tier applications * Combining the component into a workflow, and integrating

the business logic * Deploying and distributing the system over multiple systems

across the network. Six parties involved while deploying Enterprise

JavaBeans: * The Bean provider * The Container provider * The Server provider * The Application Assembler * The Deployer * The System Administrator


Summary - 2 Logical three-tier architecture of EJB:

The Client The EJB Server The Database

The EJB Container resides inside the EJB server. The container acts as a buffer between the bean and the outside world.

The main responsibilities of the container are: * Connecting clients to the beans

* Managing the life cycle of the bean The server provides the container with

network connectivity.


Summary - 3

The server and the container provide following

services to the developer * Transaction support

* Security support

* Persistence support

* Support for management of multiple instances .

An Enterprise Java Bean can be classified into:

* Session Beans

* Entity Beans

* Message-Driven Beans

Technology

Session 2 Tp2