How to validate duplicate check

[Devi-01]

Hi everyone,

I’m working on a Service Catalog item (e.g., “Software License Request”) where the user enters a license number.

My requirement is to:

* Check in real-time if the entered license number already exists in the system (e.g., in sc_req_item or a custom table)

* If a duplicate is found, show an error message immediately

* Optionally provide a link to the existing request

I’m planning to use:

* onChange Catalog Client Script

* GlideAjax

* Script Include

My questions:

1. Is this the correct/best approach for real-time validation?

2. Are there any best practices or alternative methods (like Data Policy / Business Rule)?

3. How can I efficiently return the existing record link to display in the message?

Any sample implementation or guidance would be really helpful.

Thanks in advance!

[Naveen20]

You can try as below

var LicenseValidator = Class.create();

LicenseValidator.prototype = Object.extendsObject(AbstractAjaxProcessor, {

checkDuplicate: function() {

var lic = (this.getParameter('sysparm_license') || '').trim();

var result = { exists: false };

if (!lic) return JSON.stringify(result);

var gr = new GlideRecord('sc_req_item');

gr.addQuery('variables.license_number', lic);

gr.addActiveQuery();

gr.setLimit(1);

gr.query();

if (gr.next()) {

result.exists = true;

result.number = gr.getValue('number');

result.url = '/nav_to.do?uri=sc_req_item.do?sys_id=' + gr.getUniqueValue();

}

return JSON.stringify(result);

},

type: 'LicenseValidator'

});

onChange Catalog Client Script on license_number:

javascript

function onChange(control, oldValue, newValue, isLoading) {

if (isLoading || !newValue || newValue === oldValue) return;

g_form.hideFieldMsg('license_number', true);

var ga = new GlideAjax('LicenseValidator');

ga.addParam('sysparm_name', 'checkDuplicate');

ga.addParam('sysparm_license', newValue);

ga.getXMLAnswer(function(response) {

var r = JSON.parse(response);

if (r.exists) {

var msg = 'License already exists on <a href="' + r.url +

'" target="_blank">' + r.number + '</a>.';

g_form.showFieldMsg('license_number', msg, 'error', true); // 4th arg = isHTML

}

});

}

Best practices

- Add a before-insert BR on sc_req_item with the same check + current.setAbortAction(true) — client scripts can be bypassed via API.

- Data Policy / UI Policy don't fit here.