WEB APPLICATION
Web application are programe that are executed on a web server and accessd from web browser . These application enable organization to share and access information information on the internet and corporate intrancts , This information can be accessed from anywhere anytime . In addtion ,Web application can support online commercial trancations , populary know as e-comerse , All online store accessed through a web browser is an example of a web application ,
In the the preceding figure a client sends request for a resourse . such as a web page or a video . on the internet . The web server interprets the client request and determine the type of resourse requested by the client . If the required resourse is found. the web server sends resourse to the client . otherwise a error message is sent to the client ,
The three Layers of a web application
All application can be broken into three layers its owns compoments and functionally , The following figure,
The Layer of web application .
An displaed in the preceding figure. an application has the following three layers
- Presentation layer:- Consists of the interface through which the users interact with the application ,
- Business Layers :- Consists of the components of the application that control the flow of
- execution and communication between the presentation layer and the data layer ,
- Data Layer:-Consists of components that expose the application data stored application data stored in database to the logic layer,
The architechure of web application is the manner in which layers are distrubuted and the way in which they communicate with each other, Most application are built by using all the three layers,
An Application can have one of the following type of architecture
- Single-tier architecture
- Two-tier architecture
- Three-tier architecture
- N-tier architecture
Single -tier architecture :-
In an application based on single -tier architecture ,all the three layers are intergerd together an can be installed on a single-tier computer . If the application needs to be accessed on multiple computers a separte instatlation is rrequired on each computer . For Example Adobe photoshope that is used creadted to and edit graphics is standards based on the single-tier archtitecture .
The following figure displays the single-tier architecture
Two Tier Architecture :-
Ina an application based on two tier architecture , the three alyerrs are distrubuted overr two tiers a client and a server. The Presebtation layer resides on each client computer , the business logic layer resides either on the client or on the server, and the data access layer resides on the server .
Depending on the businee requirements , an organization can have the following types of two tier application architecture,
- Fat client and thin client - The aarchitecture in which hte business logic resides on the client is know as the fat client and thin client server architecture , Intthis architecture the clients accepts user requests and processess the request on its own. The client communiate with the server only when the data for communication or archival needs to be sent to the server
- Fat server and Thin client - The architecture in which the business logic layer resides on the server is know as the fat server and thin client architecture , in this architecture . the client accepts from te users and forwards the same to the serverr . Futher , the server processes these requests and provides responses.
in an application based on three tier architecture , the three layers of the application are placed separaley as three different entites , The architecture is used o for those application in which meeting the business logic layer of the presentation layer of the data layer may degrade the performance of the application . To improve the application performance . the three layers are kept separley and communication among the layers with the help of a request -response mechanism,
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