J2EE Architecture Overview

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J2EE Architecture OverviewJ2EE Architecture Overview


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Unit ObjectivesUnit Objectives

Why is this topic important?

Servlets and JSP technology are important parts of J2EE

In this unit you see how Servlets and JSP fit into the wider picture

After completing this unit, you should be able to:

Understand the stages in the development of Web applicationsDescribe the model-view-controller (MVC) design pattern

Understand the importance of MVC in J2EE applications

Describe the components, containers, and services provided by a

J2EE platformDescribe the architecture of J2EE

Understand the application model for J2EE applications


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Web Browser

Web Server

File System

HTTP Request

HTTP Response

Client Network Server

Web Application EvolutionWeb Application Evolution StaticStatic

Organizations want to make their information available to as

many people in the world as possible

This can be achieved by using the Web, delivering the

information as static HTML pages


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Web Browser

with JVM

Web Server

File System

HTTP Request

HTTP Response

Client Network Server

Web Application EvolutionWeb Application EvolutionAppletsApplets

With static HTML, users see passive page presentationswhich are always the same

Presentation can be improved with Java applets or other

client-side programs


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Network

Web Browser

Web Server

File System

HTTP RequestClient Server

Web Server Plug-in

Web Container

Web Application EvolutionWeb Application Evolution ServletsServlets

Applets cannot access data on back-end systems

A Web container can provide server-side components (suchas servlets) to generate dynamic content

Requests for

dynamic

resources

Requests for

staticresources

HTTP

Response

Dynamic

response


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Request

Response

Web Container

Servlet

JavaServer Page

JavaBean

service(req,res)

methods()

methods()

forward(req,res)

RequestDispatcher

service(req,res)

Web Application EvolutionWeb Application Evolution JSP PagesJSP Pages

Servlets give poor separation between business logic andpresentation logicUse JavaServer Pages and JavaBeans to improve separation


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Web Application EvolutionWeb Application Evolution EJBsEJBs

EJBs:

Are available remotely over the network

Encapsulate business rules, application-specific logic, andaccess to data

Can be used by many different types of application

concurrentlyRepresent a central repository of business logic

WebBrowser

Java

Application

HTTPServer

EJBContainer

WebContainer


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Web Application EvolutionWeb Application Evolution ScalabilityScalability

Business requirements often involve high availability

Improved performance may be required as business grows

Both these requirements can be achieved through scalingServers can provide redundancy in the system

By sharing the load between servers, performance can be

enhanced

WebBrowser

HTTP

Server

EJBContainer

Web

Container

WebContainer

EJB

Container


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The ModelThe Model--ViewView--Controller PatternController Pattern

Model-View-Controller (MVC) is a design patternVery widely used and regarded as a core concept in J2EE

development

Various practical benefits (covered in more detail later)

Promotes code reuseReduces development time

The modelRepresents the underlying data and business logic in one place

Contains no information about the user interface

The viewThe user interface things the user can see and respond to

Represent a window into the model there can be many of these

The controllerConnects the model and the view

Used to communicate between the model and view

A fourth layer persistence is often added to the pattern


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J2EE Server

View

Controller

Database

Model

Persistence

MVCMVCApplication to J2EEApplication to J2EE

Web

Browser

Transfer

Servlet Transfer

EJB

Transfer

ResultJavaBean

HTML

Doc

HTML

Doc

5

2

3

4

6

7

1

Balance

JSP


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MVCMVC BenefitsBenefits

Promotes code reuseThe purpose of the model is to provide business logic and

data access in one place

This logic can be reused in many applications at the same

time without the need for any extra codingReduces development time

The model, view, and controller can be developed in

parallelMore maintainable

The view can be changed without affecting the modelA Web page view can be changed to display a chart instead of a table

with no change to the model

The model can be changed without affecting the viewFor example, the way in which an insurance premium is calculated may

change, but the interface to the business method remains the same

Data can be moved without affecting the view or modelThe layering concept allows for more flexibility


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J2EE IntroductionJ2EE Introduction

The Java 2 Platform Enterprise Edition (J2EE) Specificationconsists of:

The J2EE PlatformA standard platform of containers, services and communications

The J2EE Compatibility Test SuiteTo verify that a J2EE platform product complies with the standard

WebSphere Application Server 5.0 is J2EE 1.3 compatible

WebSphere Application Server 6.0 is J2EE 1.4 compatible

The J2EE Reference ImplementationFor prototyping J2EE applications and for providing an operational

definition of the J2EE platform

The J2EE BlueprintsBest practices for developing multitier, thin-client applications

J2EE is developed using the Java Community Process

Collaboration between major enterprise software vendors

IBM actively contributes to the J2EE development process


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J2EE ComponentsJ2EE Components

J2EE defines four types of components which must be

supported by any J2EE product

AppletsGraphical Java components which typically execute within a browser

Can provide a powerful user interface for other J2EE componentsApplication client components

Java programs which execute on a client machine and access other

J2EE components

Web componentsServlets and JavaServer Pages

These provide the controller and view functionality in J2EE

Enterprise JavaBeansDistributed, transactional components for business logic and databaseaccess

Component deployment can be managed using deployment

descriptors (except applets)

J2EE C i


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J2EE ContainersJ2EE Containers

J2EE defines four types of container. Containers manage the

components they contain:

Applet containerTypically provided by a browser, possibly using the Java Plug-in

Application client containerA stand-alone Java Runtime Environment

Web component containerProvided by a J2EE application server

Enterprise bean (EJB) containerProvided by a J2EE application server

J2EE components never interact with other J2EE

components directlyThey depend on the run-time support of containers

Interaction takes place using services provided by

containers

J2EE A hiJ2EE A hit t


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J2EE ArchitectureJ2EE Architecture

RMI-IIOP

J2EE M ltiti M d lJ2EE M ltiti M d l


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Enterprise

Information

Systems

Tier

J2EE Multitier ModelJ2EE Multitier Model

Relational

Databases

Middle TierClient Tier

Enterprise

Resource

PlanningSystems

Legacy

Applications

EJB

Container

(EJBs)

WebContainer

(Servlets,

JSPs,

HTML)

J2EE

Services

(JNDI, JMS,

JavaMail)

Java

Client

WebClient

Web

Client

Firewall

J2EE B fitJ2EE B fit


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J2EE BenefitsJ2EE Benefits

Standards

A wide range of standard services, components, clients,

and tools are supported

Applications are portable across J2EE platforms

DistributionProvides scalability for performance and availability

Common services

Most commonly required services are provided by J2EEservers

Component model

Good separation of development responsibilities

Good reuse of code and opportunities to share logic

between applications

Interoperability

Integration with other systems using standard protocols

J2EE St d d S iJ2EE St d d S i O iO i


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J2EE Standard ServicesJ2EE Standard Services --OverviewOverview

The standard services provided in J2EE include the following:

Hypertext Transfer Protocol (HTTP)

Remote Method Invocation/Internet Inter-ORB Protocol (RMI-IIOP)

Java Interface Definition Language (Java IDL)

Java Transaction API (JTA)

Java Message Service (JMS)

JavaMail

JavaBeans Activation Framework (JAF)

Java API for XML Parsing (JAXP)Web Services (including JAX-RPC and SAAJ)

J2EE Connector Architecture (JCA)

Java Authentication and Authorization Service (JAAS)

Java Authorization Service Provider Contract for Containers (JACC)Two services previously in J2EE now in J2SE in version 1.4:

JDBC (relational database connectivity)

JNDI (Java Naming and Directory Interface)

J2SE Standard Ser icesJ2SE Standard Services JNDIJNDI


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J2SE Standard ServicesJ2SE Standard Services --JNDIJNDI

Java Naming and Directory Interface

Standard Extension JNDI provides directory and naming

functionality

The API is independent of the directory

implementation JNDI enables applications to discover

and retrieve objects of any type

JNDI is used to register EJBs and to

access server-provided objects

J2SE Standard ServicesJ2SE Standard Services JDBCJDBC


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J2SE Standard ServicesJ2SE Standard Services --JDBCJDBC

JDBC is an API that provides vendor-

independent connectivity to a variety ofrelational databases

JDBC functionality provides basic

connectivity and core database-related

classes

The Standard Extension providesadditional functionality

The Java Naming and Directory

Interface (JNDI) can be used to

manage data sources and connections

Connection pooling can be provided bydatabase vendors to enhance

performance, particularly for server

applications

Support for distributed transactions,

including support for the standard two-

phase commit protocol used by the

Java Transaction API (JTA)

J2EE Standard ServicesJ2EE Standard Services CommunicationsCommunications


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J2EE Standard ServicesJ2EE Standard Services --CommunicationsCommunications

Hypertext Transfer Protocol

The HTTP client-side API isdefined by the java.netpackage

The server-side API is defined bythe Servlet and JSP interfaces

The client- and server-side APIsalso support HTTP over securesockets (HTTPS)

RMI-IIOP

Allows RMI-style programmingindependent of protocol

Implementation supports boththe RMI protocol (JRMP) andCORBA IIOP

Java IDL Allows J2EE components to

invoke external CORBA objectsusing IIOP, which may be written

in any language

J2EE Standard ServicesJ2EE Standard Services JTAJTA


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J2EE Standard ServicesJ2EE Standard Services --JTAJTA

Java Transaction API Standard

Extension JTA specifies interfaces between

a transaction manager and the

parties involved in a distributed

transaction systemThe application, the resource

manager, and the application

server

JTA is implementation-neutral For application developers, theUserTransaction interface is

the key

Application developers normally

want to use container-managed

transaction demarcation, instead

of using JTA

J2EE Standard ServicesJ2EE Standard Services - MessagingMessaging


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J2EE Standard ServicesJ2EE Standard Services --MessagingMessaging

Java Messaging Service Standard Extension

The Java Message Service is a standard,vendor-neutral API used to access

enterprise message systems

Analogous to JDBC for databases

Allows for the delivery of asynchronousmessages in an applicationThe JMS client sending the message does

not have to wait until the message has been

processedJavaMail Standard Extension and JAF

JavaMail is used to add e-mail capability to

applications

Includes classes which encapsulate

common mail functions and protocols

Uses the JavaBeans Activation Framework

to encapsulate message data

J2EE Standard ServicesJ2EE Standard Services -- JAXPJAXP


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J2EE Standard ServicesJ2EE Standard Services --JAXPJAXP

Java API for XML Parsing (JAXP)

JAXP enables applications to parseand transform XML documents

Independent of XML processor

implementation

JAXP includes industry standard

components DOM (Document Object Model)

SAX (Simple API for XML Processing)

XSLT (XML Style Language

Transformations)

JAXP adds additional functionalitybeyond these standards

Java API for XML Remote Procedure

Call (JAX-RPC)

Enables Java applications

incorporating XML-based RPCfunctionality according to the SOAP

(Simple Object Access Protocol) 1.1

specification

Java API for XML Registries (JAX-R)

APIs to access UDDI Registry

J2EE Standard ServicesJ2EE Standard Services -- Web ServicesWeb Services


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J2EE Standard ServicesJ2EE Standard Services --Web ServicesWeb Services

Web Services now part of J2EE 1.4

JAX-RPC 1.1

JAX-R

Web Services for J2EE specification (JSR 109)

Standard deployment model of Web Servicesapplication within a J2EE Application Server

WS-I Basic Profile 1.0Guidelines for interoperability in a heterogeneous

environmentSAAJ 1.1 SOAP with attachments API for Java

J2EE Standard ServicesJ2EE Standard Services -- ConnectorsConnectors


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J2EE Standard ServicesJ2EE Standard Services --ConnectorsConnectors

J2EE Connector Architecture (JCA)

Allows resource adapters thatsupport access to Enterprise

Information Systems (EIS) to be

plugged into J2EE products

Defines a connectionmanagement contract between a

J2EE server and a resource

adapter to allow connection

pooling to EIS systems Defines a transaction

management contract between

the transaction manager and an

EIS that supports transactionalaccessAlso supports transactions that

are managed entirely by an EIS

Defines a security contract that

enables secure access to an EIS

J2EE Standard ServicesJ2EE Standard Services -- JAASJAAS


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J2EE Standard ServicesJ2EE Standard Services -JAASJAAS

Java Authentication and Authorization Service

(JAAS)JAAS can be used for two purposes:

Authentication of users, to reliably and securely determine

who is currently executing Java code, regardless of how

the code is running Authorization of users to ensure they have the

permissions required to do the actions performed

JAAS authentication is pluggable Java applications using JAAS remain independent from

underlying authentication technologies

JAAS authorization extends the existing Java

security architecture Access control can be based not just

on what code is running, but also onwho is running it

Java Authorization Service Provider Contract

for Containers (JACC) Allows custom authorization service providers to be

plugged into the Application Server

J2EE Standard ServicesJ2EE Standard Services -- ContainersContainers


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J2EE Standard ServicesJ2EE Standard Services ContainersContainers

Different containers have different service requirements

!!"!JAAS 1.0

!!"!Web Services

!!""JACC

!!""JCA 1.5

!!"!JAXP 1.1

!!""JAF 1.0

!!""JavaMail 1.3!!""JTA 1.0

!!"!JMS 1.1

"!""JSP 2.0"!""Servlet 2.4

!! (client)"! (client)EJB 2.1

EJBWebAppletAppl ClientOptional Package

J2EE InteroperabilityJ2EE Interoperability


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J2EE InteroperabilityJ2EE Interoperability

The J2EE platform includes interoperability requirements

J2EE may be used to integrate systemsApplications written in different languages, like C++ or Visual Basic

Applications running on different platforms, such as PCs or UNIX

workstations

Stand-alone Java-based applications that are not directly supported by

J2EE

The interoperability requirements of J2EE make this

possibleJ2EE applications can connect to legacy systems using CORBA or low-level socket interfaces

J2EE applications can connect to other J2EE applications across

multiple J2EE productsInteroperability is achieved through the use of standard

protocols for communication and data transfer

J2EE Platform RolesJ2EE Platform Roles


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J2EE Platform RolesJ2EE Platform Roles

J2EE defines the following roles

J2EE product provider Implements a J2EE product that provides containers,

APIs, and other features

Application component provider

Produces application building blocks (HTMLdocuments, EJBs, JSPs, and so forth)

In many cases this role will be further subdivided

Application assemblerTakes components developed by component

providers and assembles them into complete a J2EE

application

DeployerDeploys, configures, and runs EJBs and Web

applications System administrator

Configures and administers the infrastructure

Tool provider

Provides application component development andpackaging tools

J2EE ImplementationJ2EE Implementation


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J2EE Implementationp

The J2EE Compatibility Test Suite

Includes over 15000 tests for J2EE 1.4

Tests a candidate platform for J2EE compatibilityChecks that all the necessary operations (for example, in required

APIs) are possibleChecks that the behavior of the APIs meets the specification

Checks end-to-end compatibility by performing operations on J2EE

components and back-end systems and checking the results

Ensures portability between platformsThe J2EE Reference Implementation

Provides an operational definition of the J2EE platformThe purpose is to validate the specification and act as a reference for

J2EE platform providersCan be used by developers to confirm portability

Included as a binary with the J2EE Software Development

Kit (free for development and testing)

Unit SummaryUnit Summary


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yy

This unit covered the following topics:

The stages in the development of Web applications

The model-view-controller (MVC) design pattern

The importance of MVC in J2EE applications

The components, containers, and services provided by aJ2EE platform

The architecture of J2EE

The application model for J2EE applications

CheckpointCheckpoint


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pp

1. Briefly describe the MVC pattern.

2. What are the four J2EE containers?

3. List the full names and purposes of the following J2EEservices: JCA

JTA

JAXP JMS

J2EE Architecture Overview

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