LWC Continuation Issue: Apex methods for continuation can not be invoked from a non-continuation action

Question

I`m trying to call Continuation method from Apex that has

@AuraEnabled(continuation=true cacheable=true)

but getting next error:

Apex methods for continuation can not be invoked from a non-continuation action.

Here is the .js code that calls Apex:

    proceedToBillingData() {
//unnecessary code skipped
    getCart({ paymentData: JSON.stringify(this.pricingOption) })
                .then(cartResult => {
                    getCCLogs(cartResult.logs);
                    this.isCartAvailable = true;
                    this.cartEncryptedId = cartResult.cartEncId;
                    return getTotalNetPriceFromSAP({ cartEncId: cartResult.cartEncId });
                })
                .then(sapResult => {
                    //TODO: obtain result from SAP
                    this.totalPrice = this.userFormatter.format(sapResult['ccrz__Price__c']);
                    this.vat = ((sapResult['ccrz__Price__c'] - this.pricingOption.exclVATPrice) / sapResult['ccrz__Price__c']) * 100;
                    this.isLoading = false;
                })
                .catch(error => {
                    console.error('error --- ', error);
                    this.isLoading = false;
                    this.isError   = true;
                    this.errors    = error.body.message;
                });
}

getTotalNetPriceFromSAP() - is Continuation method

Apex code:

@AuraEnabled(continuation=true cacheable=true)
    public static Map<String, Object> getTotalNetPriceFromSAP(final String cartEncId) {
        //TODO: replace the code below with results from SAP callout using Continuation
        List<ccrz__E_Cart__c> openCart = [SELECT ccrz__Account__r.SAP_Customer_Number__c,
                                                (SELECT ccrz__Quantity__c FROM ccrz__E_CartItems__r)
                                          FROM ccrz__E_Cart__c WHERE ccrz__EncryptedId__c = :cartEncId];
        if (openCart[0].ccrz__E_CartItems__r.isEmpty()) {
            throw CustomException.setErrorMessage(String.format(CustomException.NO_CART_ITEMS_BY_USER_ID, new String[] { currentUser.Id }));
        }
        try {
            Continuation continuation = (Continuation) CC_EpayVatSimulate.startOrderSimulate(openCart[0]);
            System.debug('getTotalNetPriceFromSAP --- ' + continuation);
            return new Map<String, Object> { SObjectType.ccrz__E_CartItem__c.fields.ccrz__Price__c.Name => openCart[0].ccrz__E_CartItems__r[0].ccrz__Price__c };
        } catch (Exception e) {
            CustomException.setErrorMessage(e.getMessage());
        }
    }

The method is not being executed because of that error. If I remove the annotation params

(continuation=true cacheable=true)

it works, the method, not Continuation.

What could be the reason of this? Is the lwc action must be @wire only and not on-demand bcoz there is cacheable=true param?

Answer 1

The issue was in lwc import.

import getTotalNetPriceFromSAP from '@salesforce/apex/SFMS_SubscriptionsOverviewController.getTotalNetPriceFromSAP';

But for Continuation it must be:

import getTotalNetPriceFromSAP from '@salesforce/apexContinuation/SFMS_SubscriptionsOverviewController.getTotalNetPriceFromSAP';

Import

apexContinuation

This question is closed.

Answer 2

Your method ** getTotalNetPriceFromSAP** does not return continuation.

Understanding continuation: Apex method sends request to external system and forgets about it (it does not wait for response). In below method, startRequest returns continuation. Observe con.continuationMethod='processResponse'. This means whenever the response is returned, method processResponse is invoked.

@AuraEnabled(continuation=true cacheable=true)
public static Object startRequest() {
    Continuation con = new Continuation(40);
    con.continuationMethod='processResponse';
    HttpRequest req = new HttpRequest();
    req.setMethod('GET');
    req.setEndpoint(LONG_RUNNING_SERVICE_URL);
    con.state = con.addHttpRequest(req);
    return con;  
}

processResponse method:

@AuraEnabled(cacheable=true)
public static Object processResponse(Object state) {
    HttpResponse response = Continuation.getResponse((String)state);
    return response.getBody();
}

Note: timeout mentioned while initialising continuation is stored by continuation server, not apex method and hence I said it forgets the request.