<!----setCallBackCheck.cmp-->
<aura:component controller="LtngServerSideController">
<aura:attribute name="accountName" type="String"/>
<ui:outputText value="{!v.accountName}"/>
<ui:button press="{!c.getName}" label="Get A Name"/>
</aura:component>
/*--------setCallBackCheckController.js------*/
({
getName : function(component, event, helper) {
var action = component.get("c.getAccountName");
$A.enqueueAction(action);
action.setCallback(this,function(response)){
var status = response.getStatus();
if(status === "SUCCESS"){
component.set("v.accountName", response.getReturnValue());
}
}
})
/*--------setCallBackCheckController.apxc------*/
public class LtngServerSideController {
@AuraEnabled
public static string getAccountName(){
List<account> accounts = [SELECT Id, Name FROM Account LIMIT 1];
return accounts[0].Name;
}
}

Best Answer
There are some issues with the client-side javascript controller that you wrote for your component.
Here is the corrected code:
I would recommend going through documentation on how to call apex methods from lightning component controllers.
Hope this helps.