subscribingToTopic.java

// Snippet of code used to evict invoices cache when mqtt messages arrive. We assume we have an mqttComponent and 
// an invoiceService correctly defined in the current scope


mqttComponent.subscribeToTopicWithEmptyPayload("caches/invoices/+/evict",evictInvoiceCache(),1);

// ...

private Function<String,Void> evictInvoiceCache() {
 return topic->{
            Pattern pattern = Pattern.compile("\\d+");
            Matcher matcher = pattern.matcher(topic);
            matcher.find();
            invoiceService.evictInvoicesCache(matcher.group());
            return null;
        };
}