❑ The AJAX JavaScript
❑ The AJAX Server Page
AJAX can be used for interactive communication with a database. Demonstrates how a Web page can fetch infor-mation from a database with AJAX technology.
The preceding example contains a simple HTML form and a link to a JavaScript:
<html>
<head>
<script type="text/javascript" src="selectcustomer.js"></
script>
</head>
<body>
<form>
Select a Customer:
<select name="customers" onchange="showCustomer(this.
value)">
<option value="ALFKI">Alfreds Futterkiste</option>
<option value="NORTS ">North/South</option>
<option value="WOLZA">Wolski Zajazd</option>
</select>
</form>
<div id="txtHint"><b>Customer info will be listed here.</
b></div>
</body>
</html>
As you can see, it is just a simple HTML form with a drop-down box called
customers.
The <div> below the form will be used as a placeholder for info retrieved from the
Web server.
When the user selects data, a function called showCustomer() is executed. The
execution of the function is triggered by the “onchange” event. In other words,
each time the user changes the value in the drop-down box, the function show-Customer() is called.
the aJaX Javascript
This is the JavaScript code stored in the file selectcustomer.js:
var xmlhttp
function showCustomer(str)
{
xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
{
alert ("Your browser does not support AJAX!");
return;
}
var url="getcustomer.asp";
url=url+"?q="+str;
url=url+"&sid="+Math.random();
xmlhttp.onreadystatechange=stateChanged;
xmlhttp.open("GET",url,true);
xmlhttp.send(null);
(continued)
}
function stateChanged()
{
if (xmlhttp.readyState==4)
{
document.getElementById("txtHint").innerHTML=xmlhttp.
responseText;
}
}
function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
{
// code for IE7+, Firefox, Chrome, Opera, Safari
return new XMLHttpRequest();
}
if (window.ActiveXObject)
{
// code for IE6, IE5
return new ActiveXObject("Microsoft.XMLHTTP");
}
return null;
}
the aJaX server page
The server page called by the previous JavaScript script is an ASP file called getcus-tomer.asp.
The ASP page is written in VBScript for an Internet Information Server (IIS). It
could easily be rewritten in PHP or some other server language.
The code runs a query against a database and returns the result in an HTML table:
<%
response.expires=-1
sql="SELECT * FROM CUSTOMERS WHERE CUSTOMERID="
sql=sql & "'" & request.querystring("q") & "'"
(continued)
set conn=Server.CreateObject("ADODB.Connection")
conn.Provider="Microsoft.Jet.OLEDB.4.0"
conn.Open(Server.Mappath("/db/northwind.mdb"))
set rs=Server.CreateObject("ADODB.recordset")
rs.Open sql,conn
response.write("<table>")
do until rs.EOF
for each x in rs.Fields
response.write("<tr><td><b>" & x.name & "</b></td>")
response.write("<td>" & x.value & "</td></tr>")
next
rs.MoveNext
loop
response.write("</table>")
%>
❑ The AJAX Server Page
AJAX can be used for interactive communication with a database. Demonstrates how a Web page can fetch infor-mation from a database with AJAX technology.
The preceding example contains a simple HTML form and a link to a JavaScript:
<html>
<head>
<script type="text/javascript" src="selectcustomer.js"></
script>
</head>
<body>
<form>
Select a Customer:
<select name="customers" onchange="showCustomer(this.
value)">
<option value="ALFKI">Alfreds Futterkiste</option>
<option value="NORTS ">North/South</option>
<option value="WOLZA">Wolski Zajazd</option>
</select>
</form>
<div id="txtHint"><b>Customer info will be listed here.</
b></div>
</body>
</html>
As you can see, it is just a simple HTML form with a drop-down box called
customers.
The <div> below the form will be used as a placeholder for info retrieved from the
Web server.
When the user selects data, a function called showCustomer() is executed. The
execution of the function is triggered by the “onchange” event. In other words,
each time the user changes the value in the drop-down box, the function show-Customer() is called.
the aJaX Javascript
This is the JavaScript code stored in the file selectcustomer.js:
var xmlhttp
function showCustomer(str)
{
xmlhttp=GetXmlHttpObject();
if (xmlhttp==null)
{
alert ("Your browser does not support AJAX!");
return;
}
var url="getcustomer.asp";
url=url+"?q="+str;
url=url+"&sid="+Math.random();
xmlhttp.onreadystatechange=stateChanged;
xmlhttp.open("GET",url,true);
xmlhttp.send(null);
(continued)
}
function stateChanged()
{
if (xmlhttp.readyState==4)
{
document.getElementById("txtHint").innerHTML=xmlhttp.
responseText;
}
}
function GetXmlHttpObject()
{
if (window.XMLHttpRequest)
{
// code for IE7+, Firefox, Chrome, Opera, Safari
return new XMLHttpRequest();
}
if (window.ActiveXObject)
{
// code for IE6, IE5
return new ActiveXObject("Microsoft.XMLHTTP");
}
return null;
}
the aJaX server page
The server page called by the previous JavaScript script is an ASP file called getcus-tomer.asp.
The ASP page is written in VBScript for an Internet Information Server (IIS). It
could easily be rewritten in PHP or some other server language.
The code runs a query against a database and returns the result in an HTML table:
<%
response.expires=-1
sql="SELECT * FROM CUSTOMERS WHERE CUSTOMERID="
sql=sql & "'" & request.querystring("q") & "'"
(continued)
set conn=Server.CreateObject("ADODB.Connection")
conn.Provider="Microsoft.Jet.OLEDB.4.0"
conn.Open(Server.Mappath("/db/northwind.mdb"))
set rs=Server.CreateObject("ADODB.recordset")
rs.Open sql,conn
response.write("<table>")
do until rs.EOF
for each x in rs.Fields
response.write("<tr><td><b>" & x.name & "</b></td>")
response.write("<td>" & x.value & "</td></tr>")
next
rs.MoveNext
loop
response.write("</table>")
%>
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