In short GlideAjax is a class written by ServiceNow, that leverages the standard XMLHttpRequest - the only way to communicate with a web server after a page is loaded. To be more precise, when I say the only way, I'm talking about XMLHttpRequest.
Anyway, GlideAjax is a client side component that enables talking to the server after page load. It needs a - so called - "handler" on server side - a Script Include, that needs two characteristics:
- to extend class AbstractAjaxProcessor and
- to be marked as "Client callable":
Hint: when creating such Script Includes, always mark checkbox "Client callable" right after entering the Script Include name, before doing any modifications to the Script Include boiler plate code - only in this case the system turns the regular Script Include boiler plate into a GlideAjax suitable Script Include boiler plate.
Next one adds methods that will be "called" by the GlideAjax component; e.g:
var UserAjax = Class.create();
UserAjax.prototype = Object.extendsObject(AbstractAjaxProcessor, {
'getUsersByCostCenter': function () {
return JSON.stringify([gs.getUserID()]);
},
'type': 'UserAjax',
});
These handler methods should return strings - the only data type that can be transmitted "through the wire" (from server to client). If complex data needs to be sent through, the easiest is to "generate" an object than JSON.stringify() that object, so it becomes a string.
Of course in the final implementation one would load all users belonging to a const center and return an array with their sys_ids - here I am returning an array with a single item, the current user.
On client side, in the onChange event handler one would call this Script Include and its method as below:
function onChange (control, oldValue, newValue, isLoading, isTemplate) {
if (isLoading || newValue === '')
return;
// Indicate which Script Include contains the handler method
var gx = new GlideAjax('global.UserAjax');
// Indicate with method should be called
gx.addParam('sysparm_name', 'getUsersByCostCenter');
// Add a value to the payload - in this case the id of the Cost Center
// selected - it is assumed that this onChange event handler is for the
// variable in which the Cost Center is selected
gx.addParam('sysparm_value', newValue);
// Initiate the Ajax call indicating which function to call when the data
// from server is received by the browser
gx.getXMLAnswer(receiveUsersByCostCenter);
}
function receiveUsersByCostCenter (payload) {
// Turn the string sent by the server back into an object/array
var users = JSON.parse(payload);
g_form.setValue('<glide list variable name>', users.join(','));
// Probably:
//g_form.setValue('u_employee_names', users.join(','));
}
Well, I suppose that's actually usable already, only thing needed is to plug in the correct variable name where the setValue method is called.
Server sides in the Script Include created, in the method called, one can use this.getValue() to get to the data sent over from the client side (set by instruction gx.addParam('sysparm_value', newValue);):
var UserAjax = Class.create();
UserAjax.prototype = Object.extendsObject(global.AbstractAjaxProcessor, {
'getUsersByCostCenter': function () {
var gr = new GlideRecord('sys_user'),
users = [];
// Validate and set the query in one go
if (gr.isEncodedQueryValid('cost_center=' + this.getValue())) {
gr._query();
// Add selected users to the array which will be sent to the
// client side
while (gr._next())
users.push(gr.getUniqueValue());
}
// Return the list of users retrieved or an empty list if the user
// lookup did not succeed for some reason
return JSON.stringify(users);
},
'type': 'UserAjax',
});
Well, actually this should already solve the requirement. But note that this is not secure at all: anyone can "manually" call the same method, so you should add protection to method getUsersByCostCenter to only return data if the user qualifies, e.g. has a specific role. Unless you don't care whether any authenticated user can or cannot get the list of users belonging to any of the Cost Centers.
