Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Slide 15Slide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Slide 28Slide 29Slide 30Slide 31Slide 32Slide 33Slide 34Topic: Overview of Web Technology Course No.: CMPE 236Design of Web-Based Application Systems and ToolsInstructor: Jerry Gao, Ph.D.Copyright@1999. Jerry Gao, Ph.DIntroduction to Web Technology - Common Gateway Interface (CGI)- Java Servlet- JavaScript- JDBC- RMI- Swing and JFCCopyright@. Jerry Gao, Ph.DTopic: Overview of Web TechnologyAbout Common Gateway Interface (CGI)Copyright@. Jerry Gao, Ph.DWhat is the Common Gateway Interface (CGI)?The CGI connects Web servers to external applications.CGI can do two things. - It can gather information sent from a web browser to a web server, and make the information available to an external program.- CGI can send the output of a program to a Web browser that request it.Advantages of CGI:- Platform independence: Most web servers support CGI, including Unix: Apache, Netscape, NCSA, and CERN Windows NT: Netscape, Microsoft IIS, and O’Reilly WebSiteMacintosh: WebStar- Language independence: (Perl, TCL, C, C++ Visual Basic, AppletScript, Java)- Scalability: The simplicity of the CGI interface means that it is extremely scalable.Topic: Overview of Web TechnologyAbout Common Gateway Interface (CGI)Copyright@. Jerry Gao, Ph.DHow a CGI request is processed?Web Browser Web ServerCGI Application1. User fills out theform in the browser2. Form submittedover the Internet3. Server sendsdata to CGI application5. Server sends thepage to the browser4. CGI processes thedata and generatesthe HTML pageTopic: Overview of Web TechnologyAbout Common Gateway Interface (CGI)Copyright@. Jerry Gao, Ph.DCGI-based Architecture:InternetscriptscriptscriptWebServerWeb browserWeb browserWeb browserapplicationapplicationTopic: Overview of Web TechnologyAbout Common Gateway Interface (CGI)Copyright@. Jerry Gao, Ph.DThe limitation and problems of CGIProblems:- PerformanceEvery time a user requests a CGI script, the server must launch theCGI program, which takes processor time.When the CGI program is written in an interpreted language like Perl,then the program must run the entire Perl interpreter, and compilethe program before it can be run, which takes even more processor time.For busy web sites running complex applications, the performance problem become critical issue. - It is free. --> not easy to sell the web server products with free software.- Not good to interact with database.(connecting issue)- Not flexible or powerful to generate dynamic HTML pages.Topic: Overview of Web TechnologyAbout Java ServletCopyright@. Jerry Gao, Ph.DWhat is Java Servlets?A servlet is a Java component that can be plugged into a Java-enabled web server to provide custom services. These services include:- new features- runtime changes to content- runtime changes to presentation- new standard protocols (such as FTP)- new custom protocolsObjectives:- Servlets are designed to work within a request/response processing model.The requests can come in the form of an HTTP, URL, FTP or c custom protocol.Protocol Support:The Servlet API provides a tight link between a server and servlets. This allowsservlets to add new protocol support to a server. Any protocol that follows a request/response computing model can be implemented by a servlet. Including: HTTP, SMTP, POP, FTPTopic: Overview of Web TechnologyAbout Java ServletCopyright@. Jerry Gao, Ph.DAdvantages and Benefits:- It provide a standard approach to extending server functionality without thelimitations of CGI-based or server-specific approaches.- Java Servlets are the perfect replacement for CGI-bin scripts because of:- much less resource-intensive- more nimble or dynamic - better performance on JavaWeb Server- They are fast, safe, reliable, and 100% pure Java.Applications:Java Servlets with Applets:Work hand in hand with applets, providing a high degree of interactivityand dynamic updating. E.g. a scheduling applet, could interact with a Java Servlet to provide acommon calendar for a group of users. The applet provide interactivefeatures, such as a scrolling calendar view, that are updated by the Java Servlet dynamically. Topic: Overview of Web TechnologyAbout Java ServletCopyright@. Jerry Gao, Ph.DApplications: (Con’t)Java Servlets with Applets:Work hand in hand with applets, providing a high degree of interactivityand dynamic updating. E.g. a scheduling applet, could interact with a Java Servlet to provide acommon calendar for a group of users. The applet provide interactivefeatures, such as a scrolling calendar view, that are updated by the Java Servlet dynamically. Java Servlets for HTML Generation:- The most common for Java Servlets is to accept form input and generate HTML dynamically.- Servlets can be written to process HTML pages and customize themas they are sent to a client.Topic: Overview of Web TechnologyAbout Java ServletCopyright@. Jerry Gao, Ph.DApplications: (Con’t)Java Servlets for Middle Tiers:- The most common use of Java Servlets --> as part of middle tiersin enterprise networks, connecting SQL DB via JDBC.One advantage of middle tier processing is simply connectionmanagement. Other roles of middle tier include:- Business rule enforcement- Transaction management- Mapping clients to redundant set of servers- Supporting different types of clients such as pure HTMLand Java capable clientsJava Web Server DatabaseServerJava ServletJDBC DriverInternetAppletTopic: Overview of Web TechnologyAbout JavaScriptCopyright@. Jerry Gao, Ph.DWhat is JavaScript?JavaScript is a scripting language designed by Netscape for Netscape browsers.- JavaScript is intimately associate with the HTMP page.- Unlike Java programs, which has no access to the surrounding HTML documents,JavaScript can read and write various parts of their own documents as well as otherdocuments that the browser has open.- JavaScript also has limited access to some of the browser’s resources, includingthe history list and set the contents of fill-out forms, open- JavaScript has a large library of math and text manipulation functions, but lacksthe network communications, graphics, and window-creation functions of Java.- Java Web Server DatabaseServerJava ServletJDBC DriverInternetAppletTopic: Overview of Web TechnologyAbout JavaScriptCopyright@. Jerry Gao, Ph.DWhat is JavaScript?- JavaScript is a