public String getRandDefTopics() {
        if (defaultTopics.isEmpty()) {
            return null;
        }
        SecureRandom rand = new SecureRandom();
        return defaultTopics.get(rand.nextInt(defaultTopics.size()));
    }
getStringFromContext

@param context
@param key
@param defaultValue
@return
inlong-dataproxy/dataproxy-source/src/main/java/org/apache/inlong/dataproxy/config/CommonConfigHolder.java