Active X Microsoft’s Answer to Dynamic Content Reference: Using Active X by Brian Farrar QUE

Static Content Client www Internet Server Browser asks for a page 2- Server returns page and Browser displays

CGIs Client www Internet Server CGI program Browser invokes CGI program 2- Server runs CGI program to create page 3- Server returns result of CGI to browser to display

Does CGI make page dynamic? Yes result of whatever CGI produced created on the fly No page itself doesn’t do anything browser renders it and is finished looks like any other page

More Dynamic Activity Needed at Client Helper apps launched by browser as external program based on MIME type of file. Examples –Adobe acrobat files –Quicktime video –RealTime audio

Helper App Problems User needs to know what to download –not as much of a problem now: automatic –more software to install on client –author must figure out how to distribute code –version control maintenance problems –still widely used in past

Versions of HTML HTML 1.0 CGIs and HTML 2.0 HTML 3.0 …. STILL NO DYNAMIC CONTENT MANAGED BY THE CLIENT

Other Ways to Make Dynamic Client Pull after a delay client asks for another page to display uses tag Server Push Basically a cgi –Sends a file –delays –sends another file

Forms and CGIs Forms uses standard input controls to get user input Browser invokes the CGI indicated on the page with data from the from Server can respond to users differently! Use GET or POST methods

SUN adds dynamic content Java applets Java Java Script Hot Java Browser (not a hot item)

Java A language designed by SUN to be executed by an interpreter INSIDE THE BROWSER! Client downloads a program and executes it rather than displaying a page Any browser which adopts java can run the program - multi-platform! All major browsers quickly adopted it.

What else does Java add? Authors distribute programs over web User clicks and gets latest program rather than a static page Always the latest version Browser can be user interface for all programs Authors control distribution / authenticate

Java Applets java programs which run in the browser security concerns addressed in browser by crippling access to disk etc. Java Applications like applets run OUTSIDE the browser standalone programs compilable like c++ applications security not an issue Applets vs Applications

Java Script Whole new beast Much less powerful Allows for –user controls on form –handlers for events Dynamically and Locally control browser LOGIC in html Procedures actually at top of html source

VB Script A Microsoft thing Same concept as Java Script Only in Internet Explorer (3.0 +) NETSCAPE JavaScript Internet Explorer VBScript

Another approach Not as general as a new language Easier to display MIME types Netscape has an API to let program actually be absorbed into the browser Called PLUG-INS

A look back! Programming Development OOP/OOD RAD Tools (graphical) interprogram/process communication

Interprocess/program Communication Unix –sockets –pipes Microsoft adds –DDE –Drag n Drop OLE embedded or linked Manual –export and import

Objects and Design

Object Communication Objects interact by invoking methods and passing messages to handlers Would like to have objects ask –what another object can do –what methods are available and then use the functionality available

Similarities apps and html scripts Message/event handlers window controls but apps can be OO design extensibility Message/event handlers window controls

OLE Microsoft View Application Application & OLE object have strict boundaries ActiveX Application Application & ActiveX object have loose boundaries

Microsoft View Browser ActiveX Application Same Active X objects used in Browser AND application ActiveX Application program/design effort more usable