Ajax
<%@ page language= "java" import= "java.util.*" pageencoding= "UTF-8"%>
<script type= "Text/javascript" >
/* Standard AJAX Template */
Use false as a decision condition, which means that the XMLHttpRequest object has not yet been created
var Http_request=false;
To create a XMLHttpRequest object method
function Send_request () {
Http_request=false;
Firefox
if (window. XMLHttpRequest) {
Http_request=new XMLHttpRequest ();
if (Http_request.overridemimetype) {
Http_request.overridemimetype (' Text/xml ');
}
}else if (window. ActiveXObject) {//ie
try{
Http_request=new ActiveXObject ("msxml2.xmlhttp");
}catch (e) {
try{
Http_request=new ActiveXObject ("Microsoft.XMLHTTP");
}catch (E2) {}
}
}
if (!http_request) {//Check if request is still false (not false if all goes well)
Window.alert ("Err Create xmlhttprequest!");
}
}
Interacting with the server
function Sendreg (URL)
{
Creating an AJAX engine
Send_request ();
Set callback function
Callback functions are called automatically once the server has completed a response
Http_request.onreadystatechange = Requestreg;
Connect to Server
1. Submission Method (Get/post)
2. Submission Path (URL)
3. Whether asynchronous
Http_request.open ("Get", url,true);
Using the Get method does not cache
Http_request.setrequestheader ("If-modified-since", "0");
Submit Request
Get null
Http_request.send (NULL);
}
//Event function
Function test ()
{
//Get Data for text box
var text = document.getElementById ("text"). Value;
//get
/ /define the current Access server URL
var url = "reg?text=" + text;
//decode the string using UTF-8 encoding
URL = encodeuri (URL);
//interact with server
Sendre g (URL);
}
//define callback function
Function Requestreg ()
{
//OK State
if (http_request.readystate = = 4)
{
//Judgment response status br> if (http_request.status = =)
{
//Get data for server response
var res = http_request.responsetext;
// Note that this is done by using OUT.PRINTLN ("* * * *") in the servlet, and you can also send the data in XML format, which is var res = http_request.responsexml; You can then use the Res.getelementsbytagname and other DOM parsing methods to parse, this can be found on the Internet related information
//alert (RES);
if (res = = "true")
{
document.getElementById ("result"). InnerHTML = "<font color= ' red ' > This username has already been registered < /FONT> ";
document.getElementById ("submit"). Disabled = true;
}
Else
{
document.getElementById ("result"). InnerHTML = "<font color= ' Blue ' > This username is not registered </font > ";
document.getElementById ("submit"). Disabled = false;
}
}
}
}
</script>
<body style= "Test-align:center" onload= "Add ()" >
<table align= "center" cellspacing= "0" width= "$" border= "0" >
<tr>
<TD width= ">" username </td>
<TD width= "><input" type= "text" id= "text" onblur= "Test ()"/></td>
<TD width= "$" id= "result" ></td>
</tr>
<TR align= "center" >
<TD colspan= "2" ><input type= "button" value= "register" id= "submit" disabled= "disabled"/></td>
<td></td>
</tr>
</table>
</body>
The use of Ajax in Java
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