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Partial page refresh using Ajax

Source: Internet
Author: User
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Two files, one HTML file, and one Servlet

The HTML code is:

<HTML>
<SCRIPT>
VaR XMLHTTP;

Window. onload = function (){
// Alert ("111 ");
Dostart ();
}

Function createxmlhttprequest (){
// Alert ("222 ");
If (window. activexobject ){
XMLHTTP = new activexobject ("Microsoft. XMLHTTP ");
}
Else if (window. XMLHttpRequest ){
XMLHTTP = new XMLHttpRequest ();
}
}

Function dostart (){
// Alert ("dostart ");
Createxmlhttprequest ();
VaR url = "dyupdate. YY ";

XMLHTTP. Open ("get", URL, true );
XMLHTTP. onreadystatechange = startcallback;
XMLHTTP. Send (null );
}

Function startcallback (){
// Alert ("startcallback ");
If (XMLHTTP. readystate = 4 ){
If (XMLHTTP. Status = 200 ){
// Alert ("normal ");
SetTimeout ("pollserver ()", 5000 );
Refreshtime ();
}
Else {
Alert (XMLHTTP. status );
}
}}


Function pollserver (){
// Alert ("pollserver ");
Createxmlhttprequest ();
VaR url = "dyupdate. YY"
XMLHTTP. Open ("get", URL, true );
XMLHTTP. onreadystatechange = pollcallback;
XMLHTTP. Send (null );
}
Function pollserver2 (OB ){
// Alert (OB );
Createxmlhttprequest ();
VaR url = "dyupdate. yy & task =" + OB;
XMLHTTP. Open ("get", URL, true );
XMLHTTP. onreadystatechange = pollcallback2;
XMLHTTP. Send (null );
}
Function pollcallback2 (){}

Function pollcallback (){
// Alert ("pollcallback ");
If (XMLHTTP. readystate = 4 ){
If (XMLHTTP. Status = 200 ){
// Alert ("11 ");

VaR message = XMLHTTP. responsexml. getelementsbytagname ("message") [0]. firstchild. Data;
Alert (Message );
If (message! = ""){
VaR new_row = createrow (Message );
VaR table = Document. getelementbyid ("dyupdatearea ");
VaR table_body = table. getelementsbytagname ("tbody"). Item (0 );

VaR first_row = table_body.getelementsbytagname ("TR"). Item (1 );
Table_body.insertbefore (new_row, first_row );
SetTimeout ("pollserver ()", 5000 );
Refreshtime ();
}
Else {
Dostart ();
}}
Else {
Alert (XMLHTTP. status );
}
}
}

Function createrow (Message ){
// Alert ("createrow ");
VaR ROW = Document. createelement ("TR ");
VaR cell = Document. createelement ("TD ");
VaR cell_data = Document. createtextnode (Message );

Cell. appendchild (cell_data );
Row. appendchild (cell );
Return row;
}

Function refreshtime (){
// Alert ("refreshtime ");
VaR time_span = Document. getelementbyid ("time ");
VaR time_var = time_span.innerhtml;
VaR int_val = parseint (time_var );
VaR new_int_val = int_val-1;
 
If (new_int_val>-1 ){
SetTimeout ("refreshtime ()", 1000 );
Time_span.innerhtml = new_int_val;
} Else {
Time_span.innerhtml = 5;
}
}
</SCRIPT>
<Body>
<H1> Use Ajax <Input type = "button" value = "LOAD" id = "go" onclick = "dostart ();"/>
<P>
The page will be refreshed after <span id = "time"> 5 </span> seconds
</P>
<Table id = "dyupdatearea" align = "Left" border = "1">
<Tbody>
<Tr id = "row0">
<TD> </TD>
</Tr>
</Tbody>

<Input type = "text" id = "55" name = "text"/>
<Input type = "button" value = "Submit" onclick = "pollserver2 (document. getelementbyid ('55'). Value)"/>

</Table>
</Body>
</Html>

Servlet code:

Import java. Io. ioexception;
Import java. Io. printwriter;
Import java. util. List;
Import java. util. Collections list;

Import javax. servlet. servletexception;
Import javax. servlet. http. Cookie;
Import javax. servlet. http. httpservlet;
Import javax. servlet. requestdispatcher;
Import javax. servlet. http. httpservletrequest;
Import javax. servlet. http. httpservletresponse;
Public class Ajax extends httpservlet {
Int counter;
Private Static writable list = new writable list ();
Public void doget (httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
// Response. SETC ("UTF-8 ");
If (list. Size ()> 0)
{
System. Out. println (list. getfirst (). tostring ());
}
System. Out. println ("executed ");
// Int NO = 1;

String res = "";
String task = request. getparameter ("task ");
If (task! = NULL &&! "". Equals (task ))
List. Add (task );
String message = "12 ";
// String Reno = "<count> 0 </count> ";


// If (task. Equals ("reset ")){
// Counter = 1;
//} Else {
// Switch (Counter ){
// Case 1: Message = "1"; break;
// Case 2: Message = "2"; break;
// Case 3: Message = "3"; break;
// Case 4: Message = "4"; break;
// Case 5: Message = "5"; break;
// Default: Message = "done ";
//}
// Counter ++;
//}

If (list. Size ()> 0 ){
Message = List. removelast (). tostring ();
}
Res = "<message>" + message + "</message> ";
Printwriter out = response. getwriter ();

Response. setcontenttype ("text/XML; charset = UTF-8 ");

Response. setheader ("cache-control", "No-Cache ");
Out. println ("<response> ");
Out. println (RES );
Out. println ("</response> ");
Out. Close ();
}

// Public void dopost (httpservletrequest request, httpservletresponse response) throws servletexception, ioexception {
// String text = (string) request. getparameter ("text ");
// Response. setcontenttype ("text/XML; charset = UTF-8 ");
// If (text! = NULL)
//{
// Queue. Add (text );
//}
/// Requestdispatcher RD = This. getservletcontext (). getrequestdispatcher ("/ajax.html ");
/// RD. Forward (request, response );
//}
}

 

This article is an English version of an article which is originally in the Chinese language on aliyun.com and is provided for information purposes only. This website makes no representation or warranty of any kind, either expressed or implied, as to the accuracy, completeness ownership or reliability of the article or any translations thereof. If you have any concerns or complaints relating to the article, please send an email, providing a detailed description of the concern or complaint, to info-contact@alibabacloud.com. A staff member will contact you within 5 working days. Once verified, infringing content will be removed immediately.

Related Keywords:
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