@SuppressWarnings("unchecked")
    public Map<String, Object> getCallbackParams() {
        Map<String, Object> callbackParams =
            (Map<String, Object>) context.getAttributes().get(CALLBACK_PARAMS_KEY);

        if (callbackParams == null) {
            callbackParams = new HashMap<>();
            context.getAttributes().put(CALLBACK_PARAMS_KEY, callbackParams);
        }

        return callbackParams;
    }
@return all callback parameters added in the current request.
primefaces/src/main/java/org/primefaces/context/PrimeRequestContext.java