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Application Server & Web ServerApplication Server & Web ServerDesigned By:Designed By:



ContentsContents RecapRecap--evolutionevolution

QuestionsQuestions

Applying 3 tier architecture on web Applying 3 tier architecture on web Applying n tier architecture on web Applying n tier architecture on web

Challenges of n tier architectureChallenges of n tier architecture

Implementing the middle tierImplementing the middle tier

transaction processing (TP) monitors,transaction processing (TP) monitors, message servers,message servers,

object request brokers ( object request brokers ( ORBsORBs ) )

or application servers.or application servers.

Web Servers vs. App Servers: Choosing Between the Two Web Servers vs. App Servers: Choosing Between the Two

Primary functions of a web server and application serverPrimary functions of a web server and application server

Introduction to components and framework Introduction to components and framework



The evolution of

application architectures

Standalone - Application lives on client

Client/server Database server, client does

the thinking

Three-tier - Database, business service, client

N-tier -Database, many business services, client

Migratory architecture Intelligent agents, distributedcalculations, distributed clients



Some questions and AnswersSome questions and Answers

Q) What is a threeQ) What is a three--tier architecture?tier architecture?

A) A) A threeA three--tier architecture is any systemtier architecture is any systemwhich enforces a general separationwhich enforces a general separation

between the following three parts:between the following three parts:

1.1.Client TierClient Tier or user interfaceor user interface

2.2.Middle TierMiddle Tier or business logicor business logic

3.3.Data Storage TierData Storage Tier



Applying 3 tier architecture to web Applying 3 tier architecture to web

Applied to web applications and distributedApplied to web applications and distributed

programming, the three logical tiers usuallyprogramming, the three logical tiers usuallycorrespond to the physical separation betweencorrespond to the physical separation between

three types of devices or hosts:three types of devices or hosts:

1.1.BrowserBrowser oror GUI ApplicationGUI Application2.2.Web ServerWeb Server oror Application ServerApplication Server

3.3.Database ServerDatabase Server (often an RDBMS or(often an RDBMS or

Relational Database)Relational Database)



NN-- Tier Tier

NN--Tier: An unlimited number of tiers.Tier: An unlimited number of tiers.

Each tier may have multiple computers.Each tier may have multiple computers. Advantages:Advantages:

More powerful applicationsMore powerful applications

Many services to many clientsMany services to many clients Enhanced security, scalability and availabilityEnhanced security, scalability and availability

Disadvantages:Disadvantages:

Much more complicated to design and modelMuch more complicated to design and model

Performance risksPerformance risks

Reliability is more difficult to achieveReliability is more difficult to achieve

More difficult to maintain softwareMore difficult to maintain software



N TIER ARCH



Major quality attributesMajor quality attributes

PerformancePerformance

ReliabilityReliability UsabilityUsability

SecuritySecurity AvailabilityAvailability

ScalabilityScalability

MaintainabilityMaintainability

Effects of NEffects of N--Tier architecturesTier architectures

CCh ll f N Ti



Challenges of NChallenges of N--TierTier

ArchitecturesArchitectures•Communication and distribution is usually handled by

bought middleware (CORBA, EJB, DCOM, etc)

• Software becomes heterogeneous and parallel

• A lot to learn about the new technologies

• Distributed object application servers are

expensive (BEA's Weblogic, IBM's WebSphere)

• Designing truly reusable objects is difficult

– the design must be high quality

– they may not satisfy the needs of future systems



a enges oa enges o -- ererArchitectures (2)Architectures (2)

General distributed object protocols are slowGeneral distributed object protocols are slow

– – This is usually not important because theThis is usually not important because the

internet is so slow, and if it is, more speed caninternet is so slow, and if it is, more speed canusually be achieved by adding more hardwareusually be achieved by adding more hardware

Load balancing is quite difficult: distributingLoad balancing is quite difficult: distributing

requests to computers such that eachrequests to computers such that eachcomputer does approximately the same workcomputer does approximately the same work

In small systems, everything is simple, but inIn small systems, everything is simple, but inlargelarge

systems, the overall software design is crucial tosystems, the overall software design is crucial to

productproduct



Implementing the middle tierImplementing the middle tier

There are a variety of ways of implementingThere are a variety of ways of implementing

this middle tier, such as usingthis middle tier, such as using

transaction processing (TP) monitors,transaction processing (TP) monitors,

message servers,message servers,

object request brokers (object request brokers (ORBsORBs) (Assignment)) (Assignment)

or application servers.or application servers.



Transaction processing monitor Transaction processing monitor

TP monitor technology is software that is also referred to

as Middleware. It can provide application services tothousands of clients in a distributed client/server

environment.



Transaction monitors Transaction monitors

Transaction monitors (a.k.a. transaction processing monitors,Transaction monitors (a.k.a. transaction processing monitors,

a.k.a. TP monitors) were thea.k.a. TP monitors) were the first kind of middlewarefirst kind of middleware to supportto support

distributed transaction processing,distributed transaction processing, and thus also theand thus also the first kind of application servers.first kind of application servers.

They were (originally)They were (originally) designed fordesigned for environments withenvironments with veryvery

high processing demandshigh processing demands, such as banks or airlines, that could, such as banks or airlines, that couldnot be properly supported by 2not be properly supported by 2--tier architectures and by DBMStier architectures and by DBMS

alone.alone.

Architectures using transaction monitors as middleware forArchitectures using transaction monitors as middleware for

transaction control are also called TPtransaction control are also called TP--heavy transactionheavy transaction

processing environments, because this solution is much heavier tprocessing environments, because this solution is much heavier too

implement.implement.



TP TP--Process managementProcess management

This figure illustrates the point why process management by TP monitors is sobeneficial for performance. Assume 1000 clients are accessing a (database)

application, and each of the requests is handled individually by the DBMS. Then

the OS has to deal with the numbers given in the figure above.

By sharing resources using a TP monitor, in particular connections and processes,

the requirements for the OS are substantially reduced and the OS is fine.



TP TP TP monitor technology maps numerous client requests through TP monitor technology maps numerous client requests through

application services routines to improve system performance.application services routines to improve system performance.

The The TP monitor technology (located as a server) TP monitor technology (located as a server) can also take thecan also take theapplication transitions logic from the client.application transitions logic from the client.

This This reducesreduces the number of the number of upgradesupgrades required by these client platforms.required by these client platforms.

In addition, TP monitor technology includes numerous managementIn addition, TP monitor technology includes numerous managementfeatures, such asfeatures, such as restarting failed processesrestarting failed processes,, dynamic load balancing dynamic load balancing , and, andenforcing enforcing consistency of distributed dataconsistency of distributed data..

TP monitor technology is easily scalable TP monitor technology is easily scalable by adding more servers to meetby adding more servers to meet

growing numbers of usersgrowing numbers of users



A typical TP monitor technology providesA typical TP monitor technology provides

the ability tothe ability to update multiple differentupdate multiple different DBMSsDBMSs in ain asingle transactionsingle transaction

connectivity to a variety of data sources including flatconnectivity to a variety of data sources including flat

files, nonfiles, non--relationalrelational DBMSsDBMSs and evenand even mainframemainframe

systemssystems the ability to attach priority to transactions and to givethe ability to attach priority to transactions and to give

robust securityrobust security

For systems with thousands of users, TP monitorFor systems with thousands of users, TP monitortechnology has been one of the most effectivetechnology has been one of the most effective

solutions.solutions.



ProductsProducts

Products such as IBM CICSProducts such as IBM CICS

IMS,HPIMS,HP NonStopNonStop™™ Pathway, ACIPathway, ACI BASE24/XPNETBASE24/XPNET

BEA Tuxedo, etc.BEA Tuxedo, etc.



As client devices became intelligent and as theAs client devices became intelligent and as the

demand to integrate resources from more than onedemand to integrate resources from more than one

platform increased, there was a need to evolve TPplatform increased, there was a need to evolve TP

monitors to better meet the business needs.monitors to better meet the business needs.

Open was one attribute rarely applied to these TPOpen was one attribute rarely applied to these TPmonitors.monitors.



Message serverMessage server

A messaging server is a middleware program that handles A messaging server is a middleware program that handles

messagesmessages that are sent for use by other programs using athat are sent for use by other programs using a

messaging messaging application program interface ( application program interface ( API API ). ).

A messaging server can usually queue and prioritize messages A messaging server can usually queue and prioritize messages

as needed and saves each of the client programs from having as needed and saves each of the client programs from having to perform these services.to perform these services.



Message ServerMessage Server messaging is the exchange of messaging is the exchange of messagesmessages (specially (specially --

formatted data describing events, requests, and replies)formatted data describing events, requests, and replies)to ato a messaging servermessaging server, which acts as a message exchange, which acts as a message exchange

program for client programs.program for client programs.



ProductsProducts

IBM'sIBM's MQSeriesMQSeries and Sun Microsystems Javaand Sun Microsystems Java

Message Service ( Message Service ( JMS JMS ) are examples of products ) are examples of productsthat provide messaging interfaces and services.that provide messaging interfaces and services.



MQ SeriesMQ Series

MQ Series is "Message Oriented Middleware".MQ Series is "Message Oriented Middleware".

It uses a named queue model to implement nearIt uses a named queue model to implement near--realreal--time messaging, with guaranteed delivery. What thistime messaging, with guaranteed delivery. What this

means is that it is like email++.means is that it is like email++.

You have a sender, receiver and a message body. The You have a sender, receiver and a message body. The

big difference is that instead of a SMTP server, youbig difference is that instead of a SMTP server, you

have MQ Series.have MQ Series.



Assignment Assignment--11

Difference between TP and message serverDifference between TP and message server

A li ti



Application serverThey are also called “middleware”

• Application servers are software that

runs on the middle tier of an n-tierenvironment

• An Application Server is used to run

business logic or dynamically generatedpresentation code.

• It can either be .NET based or J2EE

based (like Oracle9iAS, BEA WebLogicServer, IBM WebSphere, JBoss).



Web Servers vs. App Servers: Web Servers vs. App Servers:

Choosing Between the TwoChoosing Between the Two Web serversWeb servers are a familiar and necessaryare a familiar and necessary

component of the Internet.component of the Internet.

Application serversApplication servers are less familiar but also aare less familiar but also a

necessary element for at least some aspects of necessary element for at least some aspects of

the Internet.the Internet.

W b d li i



Web servers and application Web servers and application

serversservers Web servers and application servers are notWeb servers and application servers are not

mutually exclusive.mutually exclusive.

And in the corporation their functions canAnd in the corporation their functions can

certainly overlap:certainly overlap:

t h e r e ar e m an y , m an y W eb ser v er s t h a t t h e r e ar e m an y , m an y W eb ser v er s t h a t a re ser v i ng d at a f r om a da t abase a re ser v i ng da ta f r om a dat abase ..

while there are more and more applicationwhile there are more and more application

servers serving up basic Web pages.servers serving up basic Web pages.



Web server and app server Web server and app server--

two different pieces of softwaretwo different pieces of software While a Web server and an application server can run on the sameWhile a Web server and an application server can run on the same

computercomputer (though usually not) these are two quite different pieces(though usually not) these are two quite different pieces

of software. There are few Web servers in common use:of software. There are few Web servers in common use: Apache takes the lionApache takes the lion’ ’ s share, while Microsoft Internet Informations share, while Microsoft Internet Information

Server (IIS) andServer (IIS) and iPlanetiPlanet Web Server are among the others.Web Server are among the others.

Application serversApplication servers jumped into the limelight only about jumped into the limelight only about two yearstwo years

agoago and there is a proliferation of products from companies suchand there is a proliferation of products from companies suchas BEA,as BEA, iPlanetiPlanet, Oracle,, Oracle, SilverStreamSilverStream, HP (Bluestone), and IBM., HP (Bluestone), and IBM.

Microsoft doesnMicrosoft doesn’ ’ t have a product it labels an application server,t have a product it labels an application server,

but the BizTalk Server is similar in functionality.but the BizTalk Server is similar in functionality.

P i f i f bP i f ti f b



Primary functions of a webPrimary functions of a web

serverserver The Web server, in general, sends Web pages to browsers as itsThe Web server, in general, sends Web pages to browsers as its

primary functionprimary function..

Most Web servers also process input from users, format data,Most Web servers also process input from users, format data,provide security, and perform other tasks.provide security, and perform other tasks.

The majority of a Web serverThe majority of a Web server’ ’ s work is to execute HTML ors work is to execute HTML or

scripting such as Perl, JavaScript, or VBScript.scripting such as Perl, JavaScript, or VBScript.



Web server Web server A Web serverA Web server handles the HTTP protocolhandles the HTTP protocol..

When theWhen the Web server receives an HTTP requestWeb server receives an HTTP request, it responds with, it responds with

an HTTP response, such as sending back an HTML page.an HTTP response, such as sending back an HTML page. To process a requestTo process a request, a Web server may respond with, a Web server may respond with

a static HTML page or imagea static HTML page or image

send a redirect, or delegate the dynamic response generationsend a redirect, or delegate the dynamic response generation

to some other program such asto some other program such as CGI scripts,CGI scripts, JSPsJSPs ((JavaServerJavaServer Pages),Pages), servletsservlets, ASPs, ASPs

(Active Server Pages), server(Active Server Pages), server--sideside JavaScriptsJavaScripts, or some, or some

other serverother server--side technology.side technology.



Web server Web server Whatever their purpose, such serverWhatever their purpose, such server--sideside

programs generate a response, most often inprograms generate a response, most often in

HTML, for viewing in a Web browser.HTML, for viewing in a Web browser.



The Web Server ModelDatabase

Server

Web

Server

Application

Server

CGI

CGI

HTTP over

TCP/IP --

The ’Net

HTTP over

TCP/IP --The ’Net

HTML

documents

VBScript, ASP,JSP

Perl, PHP, Tcl

Client browser:

HTML forms,

JavaScript,

VBScript, Java

Some application tierSome application tier



Some application tierSome application tier

technologiestechnologies

•• CGI scriptsCGI scripts-- one of the earliest server one of the earliest server --side options (supported by most webside options (supported by most web

servers)servers)-- resource intensive: a process created for every requestresource intensive: a process created for every request (heavy(heavy--

weight processes)weight processes)

•• ASP ASP (HTML embedding VBScript or JavaScript)(HTML embedding VBScript or JavaScript)

-- currently available only on Windows only via IIS (Microsoft)currently available only on Windows only via IIS (Microsoft)•• ProprietaryProprietary API API’’ss from Netscape (NSAPI), Microsoft Internetfrom Netscape (NSAPI), Microsoft Internet

Server APIServer API-- normally written in C/C++; vendor specific, fastnormally written in C/C++; vendor specific, fast

•• JavaJava ServletsServlets , Java Server pages (, Java Server pages (JSPJSP) (Referred to as) (Referred to as J2EEJ2EE))-- Wide support from Netscape, Sun, Apache, Oracle, IBM runs on moWide support from Netscape, Sun, Apache, Oracle, IBM runs on morere

than just Windowsthan just Windows

-- third party support (third party support (JRunJRun))



Delegation model of web serverDelegation model of web server Web server's delegation model is fairly simple.Web server's delegation model is fairly simple.

When a request comes into the Web serverWhen a request comes into the Web server, the Web server, the Web server

simplysimply passespasses the request to the program best able to handle it.the request to the program best able to handle it. The Web server doesn't provide any functionality beyond simplyThe Web server doesn't provide any functionality beyond simply

providing anproviding an environment in which the serverenvironment in which the server--side program canside program can

executeexecute and pass back the generated responses.and pass back the generated responses.

The serverThe server--side program usually provides for itself such functionsside program usually provides for itself such functionsasas transaction processingtransaction processing,, database connectivitydatabase connectivity, and, and messagingmessaging..



App servers App servers While aWhile a Web server may not itself supportWeb server may not itself support

transactions or database connection poolingtransactions or database connection pooling, it, it

may employ various strategies formay employ various strategies for

fault tolerancefault tolerance andand scalabilityscalability such as loadsuch as load

balancing, caching, and clusteringbalancing, caching, and clustering

——

featuresfeatures

often times erroneously assigned as featuresoften times erroneously assigned as features

reserved only forreserved only for applicationapplication servers.(seeservers.(see later)later)



Web application server Web application server--facilitiesfacilities A web application server will typically provide facilities A web application server will typically provide facilities

forfor

authenticationauthentication ("Who are you?")("Who are you?")

authorizationauthorization ("Are you supposed to be here?")("Are you supposed to be here?")

session managementsession management ("Have you been here before?")("Have you been here before?") database abstractiondatabase abstraction ("Which of these products are you("Which of these products are you

interested in?")interested in?")

presentationpresentation ("How do you want to view this?") and so on.("How do you want to view this?") and so on.



Application Server: Key Services



JBoss- Application Server

FIND SOME APPLICATION SERVERS



Apache Apache or any other commonor any other common web web serverserver cancan’’tt

handlehandle ServletsServlets nor JSP.nor JSP. So we use theSo we use the Tomcat Tomcat serverserver from thefrom the Apache Apache

subsub--project named Jakartaproject named Jakarta



Application types Application types The applications that run on an application server can be bro The applications that run on an application server can be broadly adly

classified as follows:classified as follows:

Bank or eBank or e--commerce type applicationscommerce type applications ---- These applications These applicationsconstitute the majority of those hosted on application servers.constitute the majority of those hosted on application servers. The main The mainelements they rely on areelements they rely on are JavaServer JavaServer Pages (JSP) components, JavaPages (JSP) components, Javaservletsservlets, and HTTP access. Typically, security is achieved through, and HTTP access. Typically, security is achieved through

authentication and SSL, with data requested from a database.authentication and SSL, with data requested from a database. Web service applications Web service applications ---- Many applications are built as WebMany applications are built as Web

services to enable interoperability and reuse. The main ingredieservices to enable interoperability and reuse. The main ingredients arents areHTTP access, XML transformations, JSP components, and JavaHTTP access, XML transformations, JSP components, and Java

servletsservlets..



Wireless applications Wireless applications ---- These applications are accessed from multiple These applications are accessed from multiple

devices, typically with the underlying HTTP/S transport. Becausedevices, typically with the underlying HTTP/S transport. Because many many

applications rely on alerts or notifications, JMS plays a key roapplications rely on alerts or notifications, JMS plays a key role in thele in theapplications. The main components are HTTPapplications. The main components are HTTP-- WAP [Wireless Access WAP [Wireless Access

Protocol], XML transformation, JSP components, and JavaProtocol], XML transformation, JSP components, and Java servletsservlets..

Desktop Java applicationsDesktop Java applications ---- These are thick client applications that These are thick client applications thataccess, through theaccess, through the RMI/IIOPRMI/IIOP ( ( I I nternet nternet I I nter nter - - O O RBRB P P rotocol rotocol )mechanism, )mechanism,

the business logic hosted in the EJB components.the business logic hosted in the EJB components.



componentcomponent

Component Component – – a replaceable part of a system thata replaceable part of a system thatprovides a clearly defined function through a set of provides a clearly defined function through a set of

interfaces.interfaces.



Characteristics of Components

– Used for specific commonly usedpurpose

– Collection of classes and interfaces

– Hidden implementation details

– Plug-and-play capability– Third-party developed, typically in binary

form

– Reusable in many applications

– Well-tested and relatively error-free

Wh t I C t St d d?



What Is a Component Standard?

• An agreed-upon format for defining interfaces andimplementations of components

• Examples:

– Microsoft COM+

– OMG’s CORBA

– Sun Microsystem’s Enterprise Java Beans (EJB)

– Database Middleware Standards (ODBC, ADO,

JDBC)

– XML/SOAP



What Is a Framework?

A collection of components, consisting of code and interfaceswritten in a specific language, that solves or helps buildapplications.

Two main competitors:

• Microsoft .NET

• Sun Java 2 Enterprise Editiion (J2EE)

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