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Computer Science 101 Web Access to Databases Overview of Web Access to Databases
Why web access to database? • Provides platform independent, remote access to the database – Viewing data – Gathering data – Updating data
Client-Server Technologies • Server: A program that provides services to other programs. It stands ready for requests and when it gets a request, it provides the service. • Client: A program requesting a service of a server program. It makes a request, gets the service, and makes use of it.
Web Browsers and Servers • Web server - This is a program that runs on the internet host computer (server). It takes requests for web pages from clients and delivers the pages back to the client. • Web browser - This is a program that runs on your local PC (client). It allows you to request web pages from an internet host.
HTML and HTTP • Hyper. Text Markup Language - Allows “marking up” a document with tags specifying appearance and structure. • Hyper. Text Transfer Protocol - Protocol used for browsers to communicate with web servers. Basically, this consists of “requests” from the browser and “responses” from the server.
Typical HTTP Request HTTP Response This is a web page Picture Browser This is a web page Web Server HTTP Request http: //website/some. html Browser interprets HTML and displays page
Typical HTML Request • Client Side (Browser) • Server Side – Issues request for HTML page – Reads request from client – Receives response HTML page – Finds page on server – Interprets HTML and creates web page – Displays web page – Work is done here – Sends response page to client – Essentially a file server
Server Side Programs • Here we have compiled programs that run on the server. Examples could be Java Servlets, ASP. NET languages such as C#
Typical Server-Side Request Runs script or program on the server <% server script or program %>