Avoiding sending responses from Apex as wrapper objects

To understand how you should structure response data from the Apex controller, let's take an example of Apex code that is needed to display a list of accounts for a Lightning Component:

public class AccountController{

    @AuraEnabled

    public Static List<AccountWrapper> queryAllAccounts(){
        List<AccountWrapper> accountWrapperList = New List<AccountWrapper>();
        List<Account> myAccounts = [Select id, Name, BillingState.
                                           (Select id
                                              From Contacts)
                                      From Account];
        if(!myAccounts.isEmpty()){
            for(Account currentAccount : myAccounts){
                accountWrapperList.add(new AccountWrapper (..) );
            }
        }

        return accountWrapperList;
    }

}

This is the message/wrapper class code:

public class AccountWrapper{
        @AuraEnabled

        Account currentAccount;

        @AuraEnabled
        Integer noOfContacts;

        @AuraEnabled
        Boolean isPartnerAccount;

        @AuraEnabled
        //Few more variables

        public AccountWrapper(Account currentAccount, Integer noOfContacts, Boolean isPartnerAccount,..){
        
            this.currentAccount = currentAccount;
          ....
        }
    }

Note that in this scenario the service is returning responses as a custom Apex type. It has been observed that using a JSON string as the response type improves the performance, compared to the return type of Apex that is custom-defined. The platform under the hood suffers from some performance issues, and this is more noticeable with large datasets.

Instead, we can return as the JSON, using the following code snippet:

public class AccountQueryController{

    @AuraEnabled

    public static String queryAllAccounts(){

        List<AccountWrapper> accountWrapperList = New List<AccountWrapper>();

        List<Account> myAccounts = [Select id, Name, BillingState.
                                           (Select id
                                              From Contacts)
                                      From Account];

        return JSON.serialize(myAccounts);

        }

You can then parse the string response into a valid JavaScript object, using JSON.parse() on the JavaScript. It has been observed that the performance is significantly improved via this method.