1 Web/Database Integration with Active Server Pages 15th/16th October 1998 Nick Gould Faculty of Economic and Social Studies

2 Aim of Course Provide Introduction to Active Server Pages technology. Demonstrate how to produce interactive Web Pages. Demonstrate how to develop Web-based interfaces to databases.

3 Course Structure Slides and example code. “Hands-on” development of applications using example databases.

4 ASP can be used to Develop interactive Web applications Process HTML forms Interface with databases –Search –Add records –Modify records –Delete records

5 What is an Active Server Page? Text file containing –Scripting language and –standard HTML Resides on Web server Processed by Web server when called by browser.

6 An ASP contains Scripting language code –Default is VBScript –can use Jscript, Perl 2. HTML VBScript contained in Browser sees only HTML –Server side scripting –Browser independent

7 What do we need to run ASP? Web server –Microsoft NT running IIS version 3 or later –Windows 95 running PWS –Other platforms? ASP is a component of the Web Server Server configuration –Directory containing ASPs must have Execute rights.

8 Why use Active Server Pages? Easy to develop applications No extra software required Powerful and flexible Browser independent Why Not use ASP? –Runs only on Microsoft platforms –Requires programming skills

9 Running an Active Server Page Make sure file is in an “executable” directory Enter URL of ASP in browser e.g. – Only difference from static Web pages –Active server page has extension.asp

10 VBScript Subset of Visual Basic Has all the standard constructs –Decisions, Looping, Arrays,Functions Scripting language NOT a programming language –variables need not be declared. Online help –Roadmap. –Contains full VBScript reference.

11 Variables Assigned in standard way X=24 One data type - variant - handles all. Therefore the following is valid X=24 x=“Some words”

12 Outputting Variable Values <% … veg=“potato” … %> The value of veg is The value of veg is potato

13 Operators Arithmetic + add - subtract * multiply / divide ^ exponent Logical AND NOT OR String Concatenation MyName = surname & “, ” & forenames

14 Commenting Code ‘ This is a comment REM so is this REMEMBER always comment your code!

15 Decisions If…Then <% If X<0 Then %> Negative Number <% End If %> If..Then…Else If…Then…ElseIf

16 Do...While Loop Allows us to repeat statements X=10 Do While X > 0 %> <% X = X - 1 Loop

17 For…Next Loop <% FOR I = 1 TO 5 %> <% NEXT %>

18 Built-in Functions Functions take argument(s) and return a value MyWord="potato" X=Len(MyWord) MyWord is argument Len is function Functions for –string manipulation –mathematics –date and time –see Language Reference > Functions

19 User Created Procedures - Sub Subs take arguments but do not return values Sub do_string(MyString) %> The original string: The uppercased string: Number of Characters: <% End Sub Call do_string("Now is the winter of our discontent") do_string "Now is the winter of our discontent”

20 User Created Procedures - Function Functions take arguments and can return values. Function Convert(Faren) Convert = (Faren - 32) * 5 / 9 End Function To use it Temp = Convert(212)

21 Arrays - defining So far we have dealt with scalar variables. –a scalar variable stores one piece of data An array is a variable which contains one or more pieces of data Arrays are made up of elements –each element stores one piece of data Must Declare arrays –DIM MyArray(20) –MyArray can have up to 21 elements

22 Arrays - using To add elements to an Array MyArray(0)=3 MyArray(4)=“Hello” To reference

23 Reading and Writing Files Can use VBScript to read from and write to text files. Note that the Web server username will need to have appropriate file system permissions.

24 Including Files Can use include files in VBScript –Useful for Footers, Headers, Functions The code in header.inc will be placed in our ASP when executed. Need to include the relative path of the include file.

25 HTML Forms Needed for user interaction. Can be static Web page or generated by Active Server Page. Latter allows more flexibility.

26 Defining a Form Form controls Method parameter specifies how the form data is sent to the server. Can use GET or POST. Action parameter specifies name and location of the ASP which will process the form data.

27 Form Controls Forms are populated with controls –Text boxes, drop-down menus, radio buttons Each control will have a name (as specified in the HTML) and a value (entered by the user) The name and value of each control is bundled and sent to the server to be processed by the ASP. Data is sent in a Query String surname=smith&forenames=David+John&gender=1 e.g. Form.html

28 Text Box Control HTML for a text box: <INPUT TYPE="TEXT | PASSWORD” NAME="name_of_control” [VALUE="default_text"] [SIZE="width_in_characters"] MAXLENGTH="width_in_characters"] >

29 Radio Button HTML for a radio button <INPUT TYPE=“RADIO” NAME=“name_of_control” VALUE=“value” [CHECKED]> Usually grouped Visa Access Query string will be pay_by=VISA or pay_by=ACCESS

30 Hidden Controls HTML for a Hidden control Does not appear on form. Value can’t be changed by user. Useful for passing values in a chain of ASPs.

31 Sending Form Data Submit Button <INPUT TYPE="SUBMIT" [NAME="name_of_control"] [VALUE="button_text"]> On clicking the submit button data is sent to server Option name parameter allows use of multiple submit buttons.

32 Processing the Form Data The VBScript Request Object –allows access to Query String data Server Variables Query String Data Request("control_name") –returns value of the surname control –e.g. Personal.html

33 Server Variables Can also be accessed via Request object Request.Server_Variable(“variable_name”) Can return some useful information –Client IP address –Browser type –e.g. form.html See documentation for full list (browser dependent) –Object Reference > Request Object

34 HTML Form Examples Processing form data –Example age.html calls age.asp Self Calling ASP –newage.asp –useful for validation –compact

35 The Session Object Web stateless –one-off transaction –but applications need to keep user-entered data Can use Hidden fields or more usefully Session Object Session Object - Server stores session variable values.

36 Structured Query Language (SQL) Used by ASP to query database Standard database querying language Four main SQL commands –SELECT –INSERT –UPDATE –DELETE

37 SQL - SELECT SELECT surname, FROM students Returns surname and of all students SELECT surname FROM students WHERE degree_code=‘6500’ Returns surname of all students who have a degree code of 6500 SELECT * FROM students WHERE degree_code='6500' OR surname='Faye’ Returns all details of students who have a degree code of 6500 or surname of Faye.

38 SQL - SELECT 2 SELECT * FROM students WHERE forename LIKE ‘sa*’ Returns all details of students who have a forename starting sa using LIKE ‘*sa*’ would return students having the characters sa anywhere within their forename.

39 SQL - INSERT Used to add records to a table INSERT INTO students (reg_number,surname,forename,degree_code) VALUES (979924,'Blair','Tony','6500') Text data needs to be enclosed in single quotes.

40 SQL - UPDATE The UPDATE statement allows us to modify existing records in a table. UPDATE students SET forename="Peter" WHERE reg_number= changes the forename of the specified student.

41 SQL - DELETE Allows us to delete records from a table DELETE FROM students WHERE degree_code='2550’ Deletes all students who have a degree code of Generating SQL –SQL can get complex –Use MS-Access Query tool to generate SQL and paste this into your VBScript.

42 ODBC Object Database Connectivity ASP does not talk directly to the database but via ODBC. Standard interface between applications and databases. ODBC driver required for each database package. Need to register database within ODBC with a Data Source Name (DSN) ASP uses the DSN to reference the database. Type of database and its location is invisible to ASP.

43 Connecting to a database Create ODBC entry for database In VBScript –Create instance of database component. –Open a connection to the database. –Create an instance of the Recordset. –Execute the SQL statement and store the result. Example –simpledb.asp

44 Accessing a Recordset Do While Not RSlist.EOF %>, <% RSlist.Movenext Loop %> The EOF (end of file) property of the recordset is True when the last record has been passed. We reference a field in the recordset by –recordset_name(“field_name”) The Movenext method moves the pointer to the next record in the recordset. The Recordcount property returns the number of records.

45 Using Forms to Query Databases Using a text box with a WHERE clause –artist.html calls artist.asp Using Radio buttons with a WHERE clause –format.html calls format.asp Populating Controls –subject.asp calls list.asp Drill-down –newsubject.asp calls newlist.asp calls bookdetails.asp

46 Adding Records –addcds.html calls addcds.asp Error Handling –Need to provide helpful error messages –erroradd.html and erroradd.asp Validating Data –preventing errors occurring –checkadd.html and checkadd.asp –quote.html and quote.asp

47 Deleting and Updating Records Deleting Records –Use SQL DELETE command –deletecd.asp calls deleteme.asp Updating Records –Use SQL UPDATE command –listmod.asp calls changeme.asp calls update.asp

48 Summary What we’ve covered –Creating and running ASPs –Using HTML forms with ASPs –Interfacing with databases - searching and modifying What we’ve not covered –security –efficiency