one endpoint giving me error

[Ampta]

bold part is not working in my system

errors are: at com.ampta.central_shops.service.cart.CartService.initializeNewCart(CartService.java:53) ~[classes/:na] at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103) ~[na:na] at java.base/java.lang.reflect.Method.invoke(Method.java:580) ~[na:na] at org.springframework.aop.support.AopUtils.invokeJoinpointUsingReflection(AopUtils.java:355) ~[spring-aop-6.1.13.jar:6.1.13] at org.springframework.aop.framework.CglibAopProxy$DynamicAdvisedInterceptor.intercept(CglibAopProxy.java:716) ~[spring-aop-6.1.13.jar:6.1.13] at com.ampta.central_shops.service.cart.CartService$$SpringCGLIB$$0.initializeNewCart() ~[classes/:na] at com.ampta.central_shops.controller.CartItemController.addItemToCart(CartItemController.java:32) ~[classes/:na] at java.base/jdk.internal.reflect.DirectMethodHandleAccessor.invoke(DirectMethodHandleAccessor.java:103) ~[na:na] at java.base/java.lang.reflect.Method.invoke(Method.java:580) ~[na:na]

@PostMapping("/item/add") public ResponseEntity addItemToCart(@RequestParam(required = false) Long cartId, @RequestParam Long productId, @RequestParam Integer quantity){ try {

        **if (cartId == null) {
            cartId = cartService.initializeNewCart();
        }**

        cartItemService.addItemToCart(cartId, productId, quantity);
        return ResponseEntity.ok(new ApiResponse("Add Item Success", null));
    }catch (ResourceNotFoundException e){
        return ResponseEntity.status(NOT_FOUND).body(new ApiResponse(e.getMessage(), null));
    }

}

[YunussEmree]

Hey, in this code there is no auto initialize cart for default users so you can set the userid manually or integrate spring security. It will be solution for your problem.