Populate a reference field using a server-side GlideAjax lookup

Reference field population via GlideAjax requires both the sys_id AND display value to work correctly. Most developers only return the sys_id, which creates a reference field that shows the sys_id instead of the display value until the record is saved and reloaded. The platform doesn't automatically resolve display values for reference fields set via setValue() — you must provide both values explicitly.

When to use this pattern

• Auto-populating reference fields based on business rules that require server-side data access
• When the lookup logic involves joins or complex queries that exceed client script capabilities
• Populating assignee based on group membership, location-based routing, or skill-based assignment
• When you need to respect ACLs and domain separation during the lookup process

When NOT to use this pattern

• Don't use for simple lookups that can be done with g_form.getReference() — those execute synchronously on the client
• Don't use in Service Portal — use $http with REST API instead for better performance
• Don't use when the lookup can return multiple valid results — this pattern assumes one correct answer
• Don't use in onLoad scripts — users haven't made a choice yet, and it creates unnecessary server calls

Key behaviors and gotchas

• Always check isLoading parameter to prevent infinite loops when the form loads existing data
• GlideAjax responses are always strings — even null returns as the string 'null'
• Script Include security: parameters are not sanitized automatically — validate all inputs before using in queries
• Domain separation applies to both the client call and server execution — cross-domain lookups may fail silently
• Use setLimit(1) when you only need one result — prevents unnecessary database overhead
• The three-parameter setValue(field, value, displayValue) only works for reference fields — regular fields ignore the third parameter