Apex Server-Side Controller Overview

Create a server-side controller in Apex and use the @AuraEnabled annotation to enable client- and server-side access to the controller method.

Only methods that you have explicitly annotated with @AuraEnabled are exposed.

Don't store component state in your controller. Store it in a component's attribute instead.

Tip

This Apex controller contains a serverEcho action that prepends a string to the value passed in.

In addition to using the @AuraEnabled annotation, your Apex controller must follow these requirements.

Methods must be static and marked public or global. Non-static methods are not supported.
If a method returns an object, instance methods that retrieve the value of the object’s instance field must be public.

For more information, see Understanding Classes in the Apex Code Developer's Guide.

Lightning Components Developer Guide