value from javascript-controller to be used as global variable in apex controller

Question

i want to pass a string from my javascript-controller to apex controller so that it can be used as a global variable(string) in Apex controller below is the code

{.....user is selecting a group name from the list of groups and im passing the group id of the selected group to apex controller so that i can use the group id to do the further operations on the server side such as connect, disconnect, send message, get all the users from the group etc....}

i want to use the group id in more than one meethod in my apex controller

controller.js

connect:function(component, event, helper){
        var selectedItem = component.get("v.selectedvalue");
        var action = component.get("c.getGroupId");
        // want to use selectedItem as a global variable (string) in apex controller
        //action.setParams({postmsg1:selectedItem});
        $A.enqueueAction(action);
    }

any help will be appreciated

Answer 1

Each transaction is a clean slate as far as global/static variables are concerned. You can't store "state" on the server or in between requests. This has a distinct advantage that Lightning can perform much better than Visualforce (up to 10x faster, in fact). To be absolutely crystal clear, you cannot store data in global variables, as they will not persist across transactions. You must pass in the value(s) you want to use for each separate transaction/Apex call.