The above diagram shows the Gmail server architecture to understand the types of Internet applications. Initially HTML is developed to support Web Supportive Applications.Later in java to develop web supportive applications SUN invented applets.Using applet technologies we develop GUI or reports to take input from the user and show output to end user.To develop Web Applications SUN invented Servlets technology, later they also invented JSP technology as a replacement of Servlet. Applet is executed in client system browser.Servlet is executed in server system.
1) When the end user types gmail.com in his browser a request for login.html is sent to server.
2) Then the login page is sent back to the client system as a response.This login.html page is a Web Supportive Application because it is downloaded and executed in client browser.
3) The end user has to type his username and password and then he has to click Sign In button
4) The data(username and password) that is given by the user is then passed to Servlet.
5) The job of Servlet(web application) is to pass the data to Database Interaction Application and to the JSP(web application).
6) The data i.e username,password and mails of end user is present in the database, so in order to retrieve the data from the database,a Database Interaction Application is present.It uses several SQL commands like 'select' as a Query to perform storing and reading data.
7) The UID of the end user is then retrieved from the database
8) Database Interaction Application(DIA) uses select command as a Query another time to retrieve the HTML mail page.
9) The mails of the end user are then retrieved from database.
10) DIA passes the HTML mail page to servlet.
11) Servlet adds HTML in java code and passes the code to JSP
12)Servlet program is static but in order to format the html code(i.e placing the hyperlinks) that HTML page is passed to JSP and make it dynamic page and later passed to Servlet.
13)Servlet then passes the dynamic html page to the client browser
Here the log in page is Web Supportive Application and the second page is Web application.
Comment for any doubts.....
2) Then the login page is sent back to the client system as a response.This login.html page is a Web Supportive Application because it is downloaded and executed in client browser.
3) The end user has to type his username and password and then he has to click Sign In button
4) The data(username and password) that is given by the user is then passed to Servlet.
5) The job of Servlet(web application) is to pass the data to Database Interaction Application and to the JSP(web application).
6) The data i.e username,password and mails of end user is present in the database, so in order to retrieve the data from the database,a Database Interaction Application is present.It uses several SQL commands like 'select' as a Query to perform storing and reading data.
7) The UID of the end user is then retrieved from the database
8) Database Interaction Application(DIA) uses select command as a Query another time to retrieve the HTML mail page.
9) The mails of the end user are then retrieved from database.
10) DIA passes the HTML mail page to servlet.
11) Servlet adds HTML in java code and passes the code to JSP
12)Servlet program is static but in order to format the html code(i.e placing the hyperlinks) that HTML page is passed to JSP and make it dynamic page and later passed to Servlet.
13)Servlet then passes the dynamic html page to the client browser
Here the log in page is Web Supportive Application and the second page is Web application.
Comment for any doubts.....
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