Application Server & Web Server Designed By: Recap-evolution Questions Applying 3 tier architecture on web Applying n tier architecture on web Challenges of n tier architecture Contents Implementing the middle tier transaction processing (TP) monitors, message servers, object request brokers (ORBs) or application servers. Web Servers vs. App Servers: Choosing Between the Two Primary functions of a web server and application server 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, distributed calculations, distributed clients Some questions and Answers Q) What is a three-tier architecture? A) A three-tier architecture is any system 1.Client which enforces a general separation between the following three parts: Tier or user interface 2.Middle Tier or business logic 3.Data Storage Tier Applying 3 tier architecture to web Applied to web applications and distributed programming, the three logical tiers usually correspond to the physical separation between three types of devices or hosts: 1.Browser or GUI Application 2.Web Server or Application Server 3.Database Server (often an RDBMS or Relational Database) N-Tier N-Tier: An unlimited number of tiers. Each tier may have multiple computers. Advantages: More powerful applications Many services to many clients Enhanced security, scalability and availability Disadvantages: Much more complicated to design and model Performance risks Reliability is more difficult to achieve More difficult to maintain software N TIER ARCH Major quality attributes Performance Reliability Usability Security Availability Scalability Maintainability Effects of N-Tier architectures Challenges of N-Tier Architectures •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 Challenges of N-Tier Architectures (2) General distributed object protocols are slow – This is usually not important because the internet is so slow, and if it is, more speed can usually be achieved by adding more hardware Load balancing is quite difficult: distributing requests to computers such that each computer does approximately the same work In small systems, everything is simple, but in large systems, the overall software design is crucial to product Implementing the middle tier There are a variety of ways of implementing this middle tier, such as using transaction processing (TP) monitors, message servers, object request brokers (ORBs) (Assignment) or application servers. Transaction processing monitor TP monitor technology is software that is also referred to as Middleware. It can provide application services to thousands of clients in a distributed client/server environment. Transaction monitors Transaction monitors (a.k.a. transaction processing monitors, a.k.a. TP monitors) were the first kind of middleware to support distributed transaction processing, and thus also the first kind of application servers. They were (originally) designed for environments with very high processing demands, such as banks or airlines, that could not be properly supported by 2-tier architectures and by DBMS alone. Architectures using transaction monitors as middleware for transaction control are also called TP-heavy transaction processing environments, because this solution is much heavier to implement. TP-Process management This figure illustrates the point why process management by TP monitors is so beneficial 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 monitor technology maps numerous client requests through application services routines to improve system performance. The TP monitor technology (located as a server) can also take the application transitions logic from the client. This reduces the number of upgrades required by these client platforms. In addition, TP monitor technology includes numerous management features, such as restarting failed processes, dynamic load balancing, and enforcing consistency of distributed data. TP monitor technology is easily scalable by adding more servers to meet growing numbers of users TP A typical TP monitor technology provides the ability to update multiple different DBMSs in a single transaction connectivity to a variety of data sources including flat files, non-relational DBMSs and even mainframe systems the ability to attach priority to transactions and to give robust security For systems with thousands of users, TP monitor technology has been one of the most effective solutions. Products Products such as IBM CICS IMS,HP NonStop™ Pathway, ACI BASE24/XPNET BEA Tuxedo, etc. As client devices became intelligent and as the demand to integrate resources from more than one platform increased, there was a need to evolve TP monitors to better meet the business needs. Open was one attribute rarely applied to these TP monitors. Message server A messaging server is a middleware program that handles messages that are sent for use by other programs using a messaging application program interface (API). A messaging server can usually queue and prioritize messages as needed and saves each of the client programs from having to perform these services. messaging is the exchange of messages (speciallyformatted data describing events, requests, and replies) to a messaging server, which acts as a message exchange program for client programs. Message Server Products IBM's MQSeries and Sun Microsystems Java Message Service (JMS) are examples of products that provide messaging interfaces and services. MQ Series MQ Series is "Message Oriented Middleware". It uses a named queue model to implement near-realtime messaging, with guaranteed delivery. What this means is that it is like email++. You have a sender, receiver and a message body. The big difference is that instead of a SMTP server, you have MQ Series. Assignment-1 Difference between TP and message server Application server They are also called “middleware” • Application servers are software that runs on the middle tier of an n-tier environment • An Application Server is used to run business logic or dynamically generated presentation code. • It can either be .NET based or J2EE based (like Oracle9iAS, BEA WebLogic Server, IBM WebSphere, JBoss). Web Servers vs. App Servers: Choosing Between the Two Web servers are a familiar and necessary component of the Internet. Application servers are less familiar but also a necessary element for at least some aspects of the Internet. Web servers and application servers Web servers and application servers are not mutually exclusive. And in the corporation their functions can certainly overlap: there are many, many Web servers that are serving data from a database. while there are more and more application servers serving up basic Web pages. While a Web server and an application server can run on the same computer (though usually not) these are two quite different pieces of software. There are few Web servers in common use: Apache takes the lion’s share, while Microsoft Internet Information Server (IIS) and iPlanet Web Server are among the others. Application servers jumped into the limelight only about two years ago and there is a proliferation of products from companies such as BEA, iPlanet, Oracle, SilverStream, HP (Bluestone), and IBM. Microsoft doesn’t have a product it labels an application server, but the BizTalk Server is similar in functionality. Web server and app servertwo different pieces of software Primary functions of a web server The Web server, in general, sends Web pages to browsers as its primary function. Most Web servers also process input from users, format data, provide security, and perform other tasks. The majority of a Web server’s work is to execute HTML or scripting such as Perl, JavaScript, or VBScript. A Web server handles the HTTP protocol. When the Web server receives an HTTP request, it responds with an HTTP response, such as sending back an HTML page. To process a request, a Web server may respond with a static HTML page or image send a redirect, or delegate the dynamic response generation to some other program such as CGI scripts, JSPs (JavaServer Pages), servlets, ASPs (Active Server Pages), server-side JavaScripts, or some other server-side technology. Web server Whatever their purpose, such server-side programs generate a response, most often in HTML, for viewing in a Web browser. Web server The Web Server Model Database Server CGI Web Server HTTP over HTTP over TCP/IP -TCP/IP -The ’Net The ’Net Client browser: HTML forms, JavaScript, VBScript, Java Application Server HTML documents CGI VBScript, ASP,JSP Perl, PHP, Tcl Some application tier technologies • CGI scripts - one of the earliest server-side options (supported by most web servers) - resource intensive: a process created for every request (heavyweight processes) - currently available only on Windows only via IIS (Microsoft) • ASP (HTML embedding VBScript or JavaScript) • Proprietary API’s from Netscape (NSAPI), Microsoft Internet Server API • Java Servlets, Java Server pages (JSP) (Referred to as J2EE) - normally written in C/C++; vendor specific, fast - Wide support from Netscape, Sun, Apache, Oracle, IBM runs on more than just Windows - third party support (JRun) Delegation model of web server Web server's delegation model is fairly simple. When a request comes into the Web server, the Web server simply passes the request to the program best able to handle it. The Web server doesn't provide any functionality beyond simply providing an environment in which the server-side program can execute and pass back the generated responses. The server-side program usually provides for itself such functions as transaction processing, database connectivity, and messaging. App servers While a Web server may not itself support transactions or database connection pooling, it may employ various strategies for fault tolerance and scalability such as load balancing, caching, and clustering—features often times erroneously assigned as features reserved only for application servers.(see later) Webapplication server willserverprovide facilities application typically -facilities A web for authentication ("Who are you?") authorization ("Are you supposed to be here?") session management ("Have you been here before?") database abstraction ("Which of these products are you interested in?") presentation ("How do you want to view this?") and so on. Application Server: Key Services JBoss- Application Server FIND SOME APPLICATION SERVERS Apache or any other common web server can’t handle Servlets nor JSP. So we use the Tomcat server from the Apache sub-project named Jakarta Application types The applications that run on an application server can be broadly classified as follows: Bank or e-commerce type applications -- These applications constitute the majority of those hosted on application servers. The main elements they rely on are JavaServer Pages (JSP) components, Java servlets, and HTTP access. Typically, security is achieved through authentication and SSL, with data requested from a database. Web service applications -- Many applications are built as Web services to enable interoperability and reuse. The main ingredients are HTTP access, XML transformations, JSP components, and Java servlets. Wireless applications -- These applications are accessed from multiple devices, typically with the underlying HTTP/S transport. Because many applications rely on alerts or notifications, JMS plays a key role in the applications. The main components are HTTP-WAP [Wireless Access Protocol], XML transformation, JSP components, and Java servlets. Desktop Java applications -- These are thick client applications that access, through the RMI/IIOP (Internet Inter-ORB Protocol )mechanism, the business logic hosted in the EJB components. component provides a clearly defined function through a set of interfaces. Component – a replaceable part of a system that Characteristics of Components – Used for specific commonly used purpose – 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 What Is a Component Standard? • An agreed-upon format for defining interfaces and implementations 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 interfaces written in a specific language, that solves or helps build applications. Two main competitors: • Microsoft .NET • Sun Java 2 Enterprise Editiion (J2EE)
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