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Quick Review:Ajax
 
Ajax Examples

}
}
}
function getHTTPRequestObject() {
var xmlhttp;
if (window.XMLHttpRequest) {
xmlhttp = new XMLHttpRequest();
} else if (window.ActiveXObject) {
xmlhttp = new ActiveXObject(“Microsoft.XMLHTTP”);
}
return xmlhttp;
}
</script>
</head>
<body>
<form>
<p>Enter User Number:
<input size=”10" name=”User No” id=”userNo” type=”text” onblur=”showFirstLastName();”></
p>
First Name:
<input size=”10" name=”First Name” id=”firstName” type=”text”>
Last Name:
<input size=”10" name=”Last Name” id=”lastName” type=”text”></form>
</body>
</html>

The input text field for user number has “onblur” attribute, which is set to the JavaScript function “showFirstLastName ()”. This method is called every time user looses focus from the component. To show the first and last name there are two more input components of id “firstName” and “lastName” which will be updated after getting the records corresponding to the particular user using Ajax.

“showFirstLastName ()” first tries to get HTTP request object maintaining the browser compatibility. In this example, this object is stored in the variable named “xmlHttp”. Read how to get HTTP request object on page 12

Next step is to determine which method should be invoked after getting the response from the server. In this example, the method “updatepage()” is assigned for this purpose. Now the request for the JSP page “user.jsp” is forwarded to the server along with user number as parameter

user.jsp

<%
String userNumber = request.getParameter(“userNo”);
if(userNumber != null) {
response.setContentType(“text/xml”);
response.setHeader(“Cache-Control”, “no-cache”);
// For XML formatted message
if(userNumber.equals(“1”)){
response.getWriter().write(“<name>Deepak,Kumar</name>”);
}
Ajax Examples

Apr  2008 | Java Jazz Up | 19
 
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