Active Server Pages

Active Server Pages

Static Internet • In the early days of the Internet, all information sent to client’s browser was static. • Little interactivity. • Little functionality beyond simple hyperlinking.

Dynamic Internet, Part 1 (CGI) • Common Gateway Interface (CGI) permits web browsers to request execution of application on the web server. • The output of application is HTML code, which is sent to requesting browser. • Separate CGI application loaded for each request. • Development of client-side scripting languages; especially JavaScript and VBScript.

Dynamic Internet, Part 2 (ISAPI) • An alternative to CGI introduced by Microsoft. • Uses dynamic link libraries (DLL). Once loaded, DLL stays in memory and answers user requests until explicitly released from memory. • Normally faster than an equivalent CGI application.

ISAPI filter • Custom DLL in same memory space as the web server, called by web server in response to every HTTP request. • The filter tells the web server how to handle the request. • The ASAPI filter allows you to customize the web server’s response to specific types of user requests.

Examples of ASAPI filters • Security layer between client and web server. Screens client request. • Custom filter to map client’s request to different location on the server. • Custom filter to interpret information from server, and present the information in a different format. For example, ASP.DLL, which interprets server code and gives the client customized information

Active Server Pages • In ASP.DLL. • Whenever user requests a file with .asp extension, this ASAPI filter handles the interpretation. • Loads scripting language interpreter DLLs. • Executes server-side code. • Passes resulting HTML to the web server, which forwards it to the browser.

Simple example <HTML> <BODY> Hello.<BR> It is now approximately <% =Time() %> at the server. <P> <% For i = 1 to 5 %> <FONT SIZE = <% =i %> > Hello Size <% =i %> </FONT> <BR> <% Next %> </BODY> </HTML>

Output of simple example

ASP Object Model • ASP encapsulates the properties and methods of 6 objects: • Application • ASPError • Request • Response • Server • Session

Application Object • Represents the ASP application itself • One Application object for all users. • Two methods • Application_OnStart (triggered by first user) • Application_OnEnd (triggered by administrator explicitly closing application.

ASPError Object • To access properties of last error in currently executing script. • Accessible only through Server’s GetLastError method.

Request Object • Access HTML form-based data and parameters sent over the address line. • Receive HTTP cookie information. • Receive client certificate information • Get access to information in HTTP request header (via ServerVariables collection).

Response Object • Controls how data is sent to client. • Sends cookies to client, set expiration date. • Redirects user to another URL.

Server Object • Gives access to web server itself. • Set timeout variables for scripts • CreateObject method lets you create instances of server-side components. For example, ActiveX Data Objects to handle database access.

Session Object • Holds information specific to user’s current session on the web server.

Server-Side Scripting • ASP.DLL interprets code in .asp files that’s delimited with <% %>. • VBScript is the default scripting language. • If the first statement is: <% @LANGUAGE=Jscript %> you can change the scripting language.

Simple example <HTML> <BODY> Hello.<BR> It is now approximately <% =Time() %> at the server. <P> <% For i = 1 to 5 %> <FONT SIZE = <% =i %> > Hello Size <% =i %> </FONT> <BR> <% Next %> </BODY> </HTML>

Output of simple example

An example that uses Form Data <html> <body> <form method="POST" action="http://localhost/asp/ex2.asp"> <H2>Choose your options</H2> <select name="favoriteBird"> <option value="flamingo"> Flamingo <option value="robin"> Robin <option value="cardinal"> Cardinal <option value="eagle"> Eagle <option value="penguin"> Penguin <option value="bluejay"> Blue Jay </select> <BR> User Name: <input type=text name="userName"> <BR> Color: <input type=text name="favoriteColor"> <BR> <input type=submit value="Send Data"> </form> </body> </html>

The User’s View

The ASP program <HTML> <HEAD> <BODY> <% username = Request("userName") %> <% color = Request("favoriteColor") %> <% bird = Request("favoriteBird") %> <FONT COLOR='<% Response.Write color %>' > Hello, <% Response.Write userName %>. </FONT> <BR> Your favorite bird is the <% Response.Write bird %>. Here is a picture! <P> <IMG SRC=<% Response.Write bird %>.jpg> </BODY> </HTML>

What the user sees

The generated code <HTML> <HEAD> <BODY> <FONT COLOR='blue' > Hello, John Avitabile. </FONT> <BR> Your favorite bird is the eagle. Here is a picture! <P> <IMG SRC=eagle.jpg> </BODY> </HTML>

An example using file access <html> <body> <form method="POST" action="http://localhost/asp/ex3.asp"> <H2>Choose your favorite bird</H2> <select name="favoriteBird"> <option value="flamingo"> Flamingo <option value="robin"> Robin <option value="cardinal"> Cardinal <option value="eagle"> Eagle <option value="penguin"> Penguin <option value="bluejay"> Blue Jay </select> <P> <input type=submit value="Send Vote"> </form> </body> </html>

The ASP Program (part 1) <% Set fso = CreateObject("Scripting.FileSystemObject") ' ActiveX voteFile = "C:\Inetpub\wwwroot\asp\votes.txt" Set tso = fso.OpenTextFile(voteFile, 8, True) ' TextStreamObject ' 8 is append, 1 is read, 2 is write; True means create if nec. Call tso.WriteLine(Request("favoriteBird")) Call tso.Close() Set tso = fso.OpenTextFile(voteFile, 1, True) Dim vote(6) Do line = tso.ReadLine Select Case line Case "flamingo" vote(1) = vote(1) + 1 Case "robin" vote(2) = vote(2) + 1 Case "cardinal" vote(3) = vote(3) + 1 Case "eagle" vote(4) = vote(4) + 1 Case "penguin" vote(5) = vote(5) + 1 Case "bluejay" vote(6) = vote(6) + 1 End Select Loop While Not tso.AtEndOfStream

The ASP Program (part 2) Call tso.Close() %> <HTML> <HEAD> <BODY> <% bird = Request("favoriteBird") %> Your vote for <% Response.Write bird %> has been recorded. Here are the totals so far. <TABLE BORDER=2 WIDTH=50%> <TR> <TD> Flamingo </TD> <TD> <% Response.Write vote(1) %> </TD> </TR> <TR> <TD> Robin </TD> <TD> <% Response.Write vote(2) %> </TD> </TR> <TR> <TD> Cardinal </TD> <TD> <% Response.Write vote(3) %> </TD> </TR> <TR> <TD> Eagle </TD> <TD> <% Response.Write vote(4) %> </TD> </TR> <TR> <TD> Penguin </TD> <TD> <% Response.Write vote(5) %> </TD> </TR> <TR> <TD> Blue Jay </TD> <TD> <% Response.Write vote(6) %> </TD> </TR> </TABLE> </BODY> </HTML>

The generated code <HTML> <HEAD> <BODY> Your vote for eagle has been recorded. Here are the totals so far. <TABLE BORDER=2 WIDTH=50%> <TR> <TD> Flamingo </TD> <TD> 2 </TD> </TR> <TR> <TD> Robin </TD> <TD> 3 </TD> </TR> <TR> <TD> Cardinal </TD> <TD> 2 </TD> </TR> <TR> <TD> Eagle </TD> <TD> 2 </TD> </TR> <TR> <TD> Penguin </TD> <TD> 1 </TD> </TR> <TR> <TD> Blue Jay </TD> <TD> 2 </TD> </TR> </TABLE> </BODY> </HTML>

Three Tier Architecture • User Interface created using HTML, Dynamic HTML, or XML. Possibly including client-side scripts. • Web server as middle tier that manipulates data from database via SQL queries and communicates with client Web browser. • Database.

Accessing a database <html> <body> <form method="POST" action="http://localhost/asp/ex4.asp"> <P> <input type=submit value="See Vote Totals"> </form> </body> </html>

The ASP Program (part 1) <% ' Check for existing connection to Database If IsObject( Session("birdVotes_dbConn")) Then Set dbConn = Session("birdVotes_dbConn") Else Set dbConn = Server.CreateObject( "ADODB.Connection" ) Call dbConn.Open("birdVotes","","") ' ODBC registered Set Session("birdVotes_dbConn") = dbConn End If dbQuery = "SELECT * FROM Votes" ' Create recordset Set votesRS = Server.CreateObject( "ADODB.Recordset") Call votesRS.Open( dbQuery, dbConn) ' move to first record in recordset Call votesRS.MoveFirst() %>

The ASP Program (part 2) <HTML> <HEAD> <BODY> <h1> Votes Already Cast </h1> <TABLE BORDER=2 WIDTH=50%> <TR> <TH> Voter </TH> <TH> Bird </TH> </TR> <% While Not votesRS.EOF %> <TR> <TD> <% =votesRS("Voter") %> </TD> <TD> <% =votesRS("Bird") %> </TD> </TR> <% Call votesRS.MoveNext() Wend %> </TABLE> </BODY> </HTML>

The generated code <HTML> <HEAD> <BODY> <h1> Votes Already Cast </h1> <TABLE BORDER=2 WIDTH=50%> <TR> <TH> Voter </TH> <TH> Bird </TH> </TR> <TR> <TD> Babe Ruth </TD> <TD> flamingo </TD> </TR> <TR> <TD> Lou Gehrig </TD> <TD> penguin </TD> </TR> <TR> <TD> Joe DiMaggio </TD> <TD> cardinal </TD> </TR> <TR> <TD> Mickey Mantle </TD> <TD> bluejay </TD> </TR> <TR> <TD> Reggie Jackson </TD> <TD> eagle </TD> </TR> <TR> <TD> Don Mattingly </TD> <TD> flamingo </TD> </TR> <TR> <TD> Mariano Rivera </TD> <TD> penguin </TD> </TR> <TR> <TD> Derek Jeter </TD> <TD> robin </TD> </TR> <TR> <TD> Ron Guidry </TD> <TD> robin </TD> </TR> <TR> <TD> Yogi Berra </TD> <TD> robin </TD> </TR> <TR> <TD> Whitey Ford </TD> <TD> eagle </TD> </TR> </TABLE> </BODY> </HTML>

Inserting, Updating, Complex queries <html> <body> <form method="POST" action="http://localhost/asp/ex5.asp"> <H2>Choose your favorite bird</H2> <select name="favoriteBird"> <option value="flamingo"> Flamingo <option value="robin"> Robin <option value="cardinal"> Cardinal <option value="eagle"> Eagle <option value="penguin"> Penguin <option value="bluejay"> Blue Jay </select> <P> Name: <input type=text name=userName> <P> <input type=submit value="Send Vote"> </form> </body> </html>

ASP Program (part 1) <% ' Check for existing connection to Database If IsObject( Session("birdVotes_dbConn")) Then Set dbConn = Session("birdVotes_dbConn") Else Set dbConn = Server.CreateObject( "ADODB.Connection" ) Call dbConn.Open("birdVotes","","") ' ODBC registered Set Session("birdVotes_dbConn") = dbConn End If dbQuery = "SELECT * FROM Votes" ' Create recordset Set votesRS = Server.CreateObject( "ADODB.Recordset") Call votesRS.Open( dbQuery, dbConn) ' move to first record in recordset

ASP Program (part 2) Call votesRS.MoveFirst() previousVote = False message = Request("userName") & "," While Not votesRS.EOF If Request("userName") = votesRS("Voter") Then message = message + " you changed your vote from " + _ votesRS("Bird") + " to " + Request("favoriteBird") sqlString = "UPDATE Votes SET Bird = '" + Request("favoriteBird") _ + "' WHERE Voter = '" + Request("userName") + "'" dbConn.Execute(sqlString) previousVote = True End If Call votesRS.MoveNext() Wend

ASP Program (part 3) If previousVote = False Then message = message + " your vote for " + Request("favoriteBird") + _ " has been recorded" sqlString = "INSERT INTO Votes VALUES ('" + Request("userName") + _ "', '" + Request("favoriteBird") + "')" dbConn.Execute(sqlString) End If %> <HTML> <HEAD> <BODY> <% =message %> <TABLE> <TR> <TH> Bird </TH> <TH> Votes </TH> </TR>

ASP Program (part 4) <% dbQuery = "SELECT Votes.Bird, COUNT(*) AS BirdCount FROM Birds " _ "INNER JOIN Votes " + _ "ON Birds.Bird = Votes.Bird GROUP BY Votes.Bird" Set birdsRS = Server.CreateObject( "ADODB.Recordset") Call birdsRS.Open( dbQuery, dbConn) ' move to first record in recordset Call birdsRS.MoveFirst() While Not birdsRS.EOF %> <TR> <TD> <% =birdsRS("Bird") %> </TD> <TD> <% =birdsRS("BirdCount") %> </TD> </TR> <% Call birdsRS.MoveNext() Wend %> </TABLE> </BODY> </HTML>

What the User Sees

Code generated <HTML> <HEAD> <BODY> Thurman Munson, you changed your vote from robin to penguin <TABLE> <TR> <TH> Bird </TH> <TH> Votes </TH> </TR> <TR> <TD> bluejay </TD> <TD> 2 </TD> </TR> <TR> <TD> cardinal </TD> <TD> 1 </TD> </TR> <TR> <TD> eagle </TD> <TD> 2 </TD> </TR> <TR> <TD> flamingo </TD> <TD> 2 </TD> </TR> <TR> <TD> penguin </TD> <TD> 3 </TD> </TR> <TR> <TD> robin </TD> <TD> 2 </TD> </TR> </TABLE> </BODY> </HTML>

Active Server Pages