TypeError: Member ApplePayPaymentRequest.countryCode is required and must be an instance of DOMString

Question

Working on Apple Pay web implementation with Java as backed system. I am getting following josn from my backend server using Ajax call

{
    "supportedNetworks": [
        "amex",
        "discover",
        "maestro",
        "masterCard",
        "visa"
    ],
    "requiredShippingContactFields": [
        "email",
        "name",
        "phone",
        "postalAddress"
    ],
    "requiredBillingContactFields": [
        "postalAddress"
    ],
    "merchantCapabilities": [
        "supportsCredit",
        "supportsDebit",
        "supports3DS"
    ],
    "shippingContact": {
        "phoneNumber": "111-111-1111",
        "emailAddress": "[email protected]",
        "givenName": "Test",
        "familyName": "Test",
        "phoneticGivenName": null,
        "phoneticFamilyName": null,
        "addressLines": [
            "Adress"
        ],
        "subLocality": null,
        "locality": null,
        "postalCode": "123456",
        "subAdministrativeArea": null,
        "administrativeArea": "Dummy",
        "country": "United States",
        "countryCode": "US"
    },
    "billingContact": {
        "phoneNumber": "111-111-1111",
        "emailAddress": "[email protected]",
        "givenName": "Test",
        "familyName": "Test",
        "phoneticGivenName": null,
        "phoneticFamilyName": null,
        "addressLines": [
            "Adress"
        ],
        "subLocality": null,
        "locality": null,
        "postalCode": "123456",
        "subAdministrativeArea": null,
        "administrativeArea": "Dummy",
        "country": "United States",
        "countryCode": "US"
    },
    "shippingMethods": [],
    "countryCode": "US",
    "currencyCode": "USD",
    "total": {
        "label": "Hello",
        "amount": "23"
    }
}

Here is my code to create Apple Pay session

var var2= getCartPaymentRequest();
     
this.session = new ApplePaySession(3, var2);

While running this code, I am getting following error on the js

TypeError: Member ApplePayPaymentRequest.countryCode is required and must be an instance of DOMString

If I change the above code to

var request1 = {
    "supportedNetworks": [
        "amex",
        "discover",
        "maestro",
        "masterCard",
        "visa"
    ],
    "requiredShippingContactFields": [
        "email",
        "name",
        "phone",
        "postalAddress"
    ],
    "requiredBillingContactFields": [
        "postalAddress"
    ],
    "merchantCapabilities": [
        "supportsCredit",
        "supportsDebit",
        "supports3DS"
    ],
    "shippingContact": {
        "phoneNumber": "111-111-1111",
        "emailAddress": "[email protected]",
        "givenName": "Test",
        "familyName": "Test",
        "phoneticGivenName": null,
        "phoneticFamilyName": null,
        "addressLines": [
            "Adress"
        ],
        "subLocality": null,
        "locality": null,
        "postalCode": "123456",
        "subAdministrativeArea": null,
        "administrativeArea": "Dummy",
        "country": "United States",
        "countryCode": "US"
    },
    "billingContact": {
        "phoneNumber": "111-111-1111",
        "emailAddress": "[email protected]",
        "givenName": "Test",
        "familyName": "Test",
        "phoneticGivenName": null,
        "phoneticFamilyName": null,
        "addressLines": [
            "Adress"
        ],
        "subLocality": null,
        "locality": null,
        "postalCode": "123456",
        "subAdministrativeArea": null,
        "administrativeArea": "Dummy",
        "country": "United States",
        "countryCode": "US"
    },
    "shippingMethods": [],
    "countryCode": "US",
    "currencyCode": "USD",
    "total": {
        "label": "Hello",
        "amount": "23"
    }
}

this.session = new ApplePaySession(3, request1);

The only difference is between the Ajax call and hard-coded payload. Here is my Ajax call code

function getCartPaymentRequest() {
    var result = "";
    $.ajax({
        type: 'GET',
        url: ACC.config.encodedContextPath + '/checkout/payment-request',
        dataType: 'json',
        success: function (response) {
            result = response;
        },

    });
    return result;
}

The country code in my Java bean is a String and I am not sure what is the issue as same payload is accepted by Apple Pay if I hard code it