AJAX_Locking is a framework in AJAX to manage locking of object in a web application.
The idea is "stolen" from David Perelman-Hall's column appeared in DDJ issue on 8th September 2006
http://www.ddj.com/showArticle.jhtml?articleID=192700218
The idea is to use AJAX to lock, unlock and get status of records/objects, avoiding use of locks on db (or transactions).
AJAX_Locking is a class that extends HTML_AJAX_Server and implements itself the features to lock, unlock and get status via a "driver":
the default driver (AJAX_Locking_Driver_SharedMemory) uses PEAR's package System_SharedMemory as repository of locks,
you can write your own driver to achieve the same purpose, using a db or the filesystem.
To use AJAX_Locking you have to write a "server" page like the following, that instantiate the Ajax remote object:
server.php
<?php
require_once ('AJAX_Locking/AJAX_Locking.php');
require_once('AJAX_Locking/Driver/SharedMemory.php');
$driver = new AJAX_Locking_Driver_SharedMemory(10, 'file');
$server = new AJAX_Locking($driver);
$server->handleRequest();
?>
and in your client page you have to use HTML_Ajax framework to call lock, unlock and status methods provided from server.
AJAX_Locking provides its own javascript library to help to write client-side management:
test.php
<?php
$user='fabamb';
$type='test';
$id =1;
?>
<html>
<head>
<script type = 'text/javascript' src = "server.php?client=Locking,all&stub=all"></script>
<script type = "text/javascript">
var lockingCallbacks = {
count: 0,
lock: function(result) {
if (result === true) {
h.status();
} else {
h.stop();
HTML_AJAX_Util.setInnerHTML('status', 'Errore durante il lock');
}
},
unlock: function(result) {
if (result === true) {
h.status();
} else {
h.stop();
HTML_AJAX_Util.setInnerHTML('status', 'Errore durante l\'unlock');
}
},
status: function(result) {
HTML_AJAX_Util.setInnerHTML('count', this.count++);
var values = result.split('~');
switch (values[0]) {
case 'owned':
html = '<img src=owned.png align=absmiddle>In fase di modifica';
enableButton('editButton', false);
enableButton('saveButton', true);
break;
case 'locked':
html = '<img src=locked.png align=absmiddle>Bloccato da ' + values[1];
enableButton('editButton', false);
enableButton('saveButton', false);
break;
case 'unlocked':
html = '<img src=unlocked.png align=absmiddle>';
enableButton('editButton', true);
enableButton('saveButton', false);
break;
case 'timeout':
h.stop();
html = '<img src=timeout.png align=absmiddle>Fase di modifica scaduta';
enableButton('editButton', false);
enableButton('saveButton', false);
break;
}
HTML_AJAX_Util.setInnerHTML('status', html);
}
}
function enableButton(id, enabled) {
var button = document.getElementById(id);
if (button) button.disabled = !enabled;
}
var h = new AJAX_Locking_Handler(lockingCallbacks, '<?=$user?>', '<?=$type?>', <?=$id?>);
</script>
</head>
<body onload = 'h.start();'>
<div id = "count">
</div>
User: <?= $user ?><br>
Tipo <?= $type ?><br>
Id: <?= $id ?><br>
Status: <span id = "status"></span>
<br>
<button id = "editButton" type = "button" onClick = "h.lock()">Edit</button>
<button id = "saveButton" type = "button" onClick = "h.unlock()" disabled>Save</button>
<button id = "statusButton" type = "button" onClick = "h.status()">Status</button>
<br>
</body>
</html>
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