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Providing Access to Databases
on the World Wide Web
the new lab exercise
Prof.dr Slobodanka Đorđević-Kajan
mr Aleksandar Dimitrijević
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Faculty of Electronic Engineering
Introduction
Structures and Databases is a two-semester
course on undergraduated studies
Databases exercises currently includes
–
–
–
–
–
–
Lab1: ER modeling and ER-to-Relational mapping
Lab2: SQL (Create and loading tables)
Lab3: SQL (Queries)
Lab4: SQL (Update and Delete tables)
Lab5: SQL (Views and Indexes)
Lab6: Pro*C
Two new lab exercises extends basic set of
databases labs with application access to
databases
– Lab7: Data Access APIs
– Lab8: Providing Access to Databases on the World Wide Web
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Faculty of Electronic Engineering
Task
Write a Windows console application in MS
Visual C/C++ for executing a simple SQL query
(defined in previous DB exercise) on the
database using ODBC API.
Create a HTML client containing form for data
requesting.
Modify console application so that can be
executed as CGI process.
Test the application using HTML client.
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Faculty of Electronic Engineering
Prerequisites
High level of fundamental programming
skill (including exception handling)
Medium level of C/C++ programming skill
using MS Visual C/C++
Medium level of understanding HTTP
protocol, and appropriate header format
Low-Medium level of HTML syntax
knowledge
SQL syntax knowledge
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Faculty of Electronic Engineering
Goals
Introduction to ...
– ODBC API
– HTML form definition
– CGI interface and retrieving paramethers from
system variables using C++
All together – writting an application that
enables remote users to access appropriate
data source through the Internet
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ODBC
Open Database Connectivity (ODBC) is a
call-level interface that allows applications
to access data in any database for which
there is an ODBC driver.
ODBC provides an API that allows
application to be independent of the source
database management system (DBMS).
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Main MFC ODBC Classes
CDatabase
– Open()
– IsOpen()
– Close()
CRecordset
– constructor
– Open()
– IsEOF
– MoveNext()
– Close()
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CDatabase
CDatabase represents a connection to a data source
CDatabase db;
db.Open(NULL, FALSE, FALSE, _T("ODBC;Driver={Microsoft
Access Driver *.mdb)};DefaultDir=C:\\Tmp\\;DBQ=Db1.mdb"));
if(db.IsOpen())
{
....
db.Close();
}
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CRecordset
CRecordset represents a set of records selected from a data
source.
CRecordset rs(&db);
try{
if(rs.Open( CRecordset::forwardOnly, selectQuery )){
while( !rs.IsEOF( ) ){
short index = 0;
try{
CString strVal;
while(true){
rs.GetFieldValue( index, strVal );
....
index++;}
}catch(CException* e){
...
rs.MoveNext( );}
}
rs.Close( );
...
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HTML Form Creation
<HTML>
<head><title>DB klient</title></head>
<body background="bg.gif">
<FONT color="FFFFFF">
<h1>Database client - form</h1>
<form ACTION="http://localhost:3000/cgi-bin/DBServer.exe"
METHOD="GET">
Upit: <input TYPE="text" NAME="SELECT" SIZE="30"
MAXLENGTH="150">
<input TYPE="submit" VALUE="Query">
<p> Rezultati upita: </p>
<TEXTAREA NAME="RESULTS" ROWS="10" COLS="40">
</TEXTAREA>
</form>
</FONT></body>
</HTML>
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HTML Form – Database client
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Datapath
http://localhost:3000/c
gi-bin/DBServer.exe?
SELECT=SELECT+*
+FROM+Table1
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W
e
b
Env.Var.
CGI
S
e
r
v
e
r
ODBC
Database
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Receiving parameters
char* reqmethod =
getenv("REQUEST_METHOD");
char* q_string =
getenv("QUERY_STRING");
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Output
printf("Pragma: no-cache\r\n");
printf("Content-Type: text/html\r\n");
SYSTEMTIME st;
GetSystemTime( &st );
CTime timeHttp( st );
CString time=timeHttp.Format( "%a, %d %b %Y %H:%M:%S GMT" );
printf("Last-Modified: %s\r\n\r\n",time);
printf("\r\n");
printf("<HTML><head><title>DB klient</title></head>");
...
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Development Environment
Microsoft Visual C/C++
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Summary
This exercise combines elements of Web
programming and database access using
ODBC interface.
Should be carried out at the end of the
course, after finishing all other prerequisit
exercises.
Should create the foundation for including
database access in more serious projects.
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More Information ...
Like all other matherial needed in this
course, preparation for this lab can be found
on:
http://gislab.elfak.ni.ac.yu/baze/
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