Consider the Apex controller below, that is called from an Aura component:Line 5 @AuraEnabledLine 6...

When building Apex controllers for Aura Components (or Lightning Web Components), any method annotated with @AuraEnabled must be defined as static. The snippet provided defines the method getStringArray() as an instance method (public List...) rather than a static method (public static List...).

The Lightning Component framework does not instantiate an object of the Apex class; instead, it calls the method statically. If the method is not static, the framework cannot locate or execute it, resulting in an error. While global was required in older versions or for managed packages, public is sufficient for code within the same namespace. Apex handles the serialization of standard types like Lists automatically, so manual JSON serialization is not required.