Introduction

to

J2EE

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Enterprise Architecture types

Enterprise Architecture can be broken into 3 fundamental layers

• User Interface• Processing• Data Storage and access

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Types of enterprise architecture

1. Single Tier

All 3 layers of enterprise architecture exist on the same system

2.Two Tier Architecture

- All 3 layers distributed between 2 tiers

- Generally UI and business logic reside on FE and Data Access on Back end

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3. Three tier architecture

- All 3 layers separated logically

- Physical separation depends on the application

- User Interface- client end

Processing – Middle / Business Tier(Apps server)

Database - Back end

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4. n.Tier Architecture

- 2nd layer can be broken into multiple layers

User Interface

Business model

Business rules

Business object to data source mapping

Data Access

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Advantages of n tier1. Improved maintainablity : Applications can

be easily maintained

2. Consistency: In terms of component design

3. Interoperability: Supports component design in any layer and by any technology

4. Flexibility : Freedom to design any type of component

5. Scalability: Addition of new components…

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Goals of an Enterprise Architecture• Robust• Performance & Scalability• Capitalize adv of OO Design Priniciple• Avoid complexity• Maintainable and Extensible• Ease of testing• Reuse of application• Support multiple client types• Product delivery on time

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What is J2EE??

• Platform used for n tier application development

• Compliant with goals of enterprise architecture

• Based on Java 2 Platform , standard edition

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Benefits of J2EE1. Simple Architecture

- Provision of a variety of ways to configure architecture of an application

- supports component based design

( updation, replacement and addition of new functionality can be wired into existing app easily)

( Member with specific skill set develops components under his/her skill area leading to developmental modularization)

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2. Easy association with existing Information system

- includes industry accepted APIs thereby enabling to access existing Information systems(J2SE based systems)

- Wiring to existing system through

a) J2EE connector architecture

b) JDBC API

c) JNDI

d) Java Mail

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3. Freedom of server ,tool and component choice

- Organisations have plethora of choices in terms of vendors, hardware, OS,server configuration.( This has created market for servers for J2EE platform)

- Component support ensures standardized, packged and reused components.Vendors will be able to provide solutions which will be easily compatible to the current system.

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4. Scalabilty

- component design support has improved the scalabilty factor in these application

5. Security model

- EJB and Servlet provide programmatic security mechanisms

- user based security offered by application at deployment time

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Features of JEE• Platform Independence

• Managed Objects through containers

• Reusability

• Modularity

• Easy development

• Simplified EJB technology

• Enhanced Web services

• Support for web2.0

• Ease of Application packaging

• Light weight JPA(POJO based)

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JEE Runtime Infrastructure

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• Run time infrastructure is used for managing and hosting applications

• Services to manage applications are provided by runtime infrastructure.(platform level)

• Services- messaging,security and distributed transactions

• JEE accesses the APIs that provide services through containers

• J2SE provides core APIs for devloping a JEE application

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APIs in JEE1. Enterprise Java Beans (EJB3.0)

- Server side code for business logic

- types – session beans & message driven beans

- Session bean – conversation with client

- message driven bean – session bean + message

listener(asynchronous)

- Entity beans have been replaced by JPA.

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2. Java Servlet Technology 2.5

- Extends the capability of servers

- Commonly used to extend applications hosted by Web servers

3. Java Server Pages Technology 2.1

- Text document – HTML+WML+JSP elements

- Construction of Dynamic content

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4. Java Server Pages Standard Tag Library 1.1

- JSTL

- Provides standard set of JSP tags instead of mixing multiple tags by multiple vendors

- iterator and Conditional tags – control flow in XML documents

- Database access tags using SQL

- Uses JSP container

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5. Java Server Faces 1.2

- Simplifies UI build process

- server side UI building framework

- Provides a set of reusable UIs from which new UIs cn be constructed.

6. Java Message Servics 1.1

- JMS

- Componnts to send , receive and read Messages

- Lossely coupled and Asynchronous.

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7.Java Transaction API1.1

- JTA – interface for transactions

- default auto commit and rollbacks

8. Java mail 1.4

- email notifications

- 2 types – application level interface & Service provider level interface

- Java mail + service provider= Internet email

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9. JavaBeans Activation Framework1.1

- JAF

- provides service for

data identification

access encapsulation

operation identification

JavaBean creation for identification

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10. Java API for XML processing1.4(JAXP)

- Supports XML document processing using DOM,Simple API for XML,

and Extensible style sheet Language Transformation(XSLT).

11. Java API for XML web services(JAX-WS)

-provides web services

12. Java Architecture for XML binding(JAXB)

- convienient bind between XML schema and Java language programs

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13. SOAP with attachments API (SAAJ)

- Standard way to send XML documents over internet.

14. Streaming API for XML(StAX)

- Alternative to DOM,Simple API for XML, TrAX .

15. Java API for XML registeries(JAXR)

- provides access to business and general purpose regiters over web

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16. J2EE Connector Architecture

- Provides solutions for connectivity between Application servers and EIS.

17. JDBC API

- Supports SQL commands in Java programing language

18. Java Persistence API (JPA)

- Uses ORM approach to bridge gap between Object oriented model and

Relational database

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19. Java Naming and Directory Interface(JNDI)

- provides naming and directory functionality

- enables access to multiple naming and directory services

20. Java Authentication and Authorization(JAAS)

- Authenticates and Authorizes users for JEE application.

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Architecture of JEE 5

Client M/c

JEE Server

Data BaSe Server Server

Client Tier App

Client

HTML

Pages

Web Tier

Business Tier

JSP

EJB EJB

EIS Tier

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Java EE Containers

• JEE provides services in the form of a container for every component

• Containers are interfaces between components and Low level platform specific functionality

• Components should be deployed in the container before use.

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Container Types

1.EJB Container

- provides an environment in which one or more Enterprise bean will run

- Combination of classes and interfaces

- Provides EJB component with

lifecycle , state management , naming services, security mechanisms and persistence management.

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2. Web Container

- Manages JSP and Servlet

- Runtime environment for web application

- Web container is always in a web server

- provides context and lifecycle management

3. Application client Container

- Manages execution of application client components.

4. Applet Conatainer

- Manages the lifecycle of applets

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Developing Java EE 5 ApplicationSteps to develop a JEE application are

1. Develop application component

2. Compose application components into modules

3. Compose modules into application

4. Deploy application

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Developing Application component

- All the functional units (components) are designed in this phase

- component – a class / collection of classes and interfaces

- 5 types of components

EJB,servlets, JSP , applets, application client, connectors.

-

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Compose application components into modules

- process of bundling/wiring of components

-3 types of modules can be designed

1. EJB module-

-packaged and deployed as ejb-jar.xml

- contains class files for ejbs,deployment descriptor

- may contain classes and interfaces for ejbs not included in J2EE platform

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2. Web module-

- Packaged and deployed in web.xml file

- Contains class for servlets,JSP,Static documents , class for applet, web

deployment descriptor.

3. Application client module

- Packaged into jar files

- Contains class for client, application client deployment descriptor

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3. Composition of modules into application

- Java EE application is delivered as enterprise archive(ear) file.

- JEE application packages the modules and their corresponding deployment descriptors.

- application.xml is required as deployment descriptor of the entire application

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JEE application (ear file)

application.xml

Ejb module Web module Java module

Ejb module (jar)

Ejb-jar.xml

ejb

ejb

Web module (jar)

web.xml

jsp

servlet

Java module (jar)

Application client.xml

Java

Java

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4. Application Deployment

- Involves 2 steps

1. Installation of the application – the deployer copies the ear to the application server , generates additional container specific classes and interfaces

2. Configuration of the application- resolves all external dependencies and follow the application assembly instruction

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Probable Architectures

• Applet Client with JSP and Database

presentation – Applet

Business - JSP

Database - JDBC• Application Client with EJB

presentation – JFC/Console application

Business - EJB

Database - JDBC

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• JSP Client with EJB

presentation – Web Browser

Web tier - JSP

Business - EJB

Database - JDBC• Web Services for application integration

presentation – C# application

Web tier - Web Services

Business - EJB

Database - JDBC