private Integer getAsIntOrNull(String val) {
        try {
            return Integer.parseInt(val);
        } catch (@SuppressWarnings("unused") NumberFormatException exp) {
            return null;
        }
    }
Return the content of the mapping as an array with all specifications as given

@return port mappings as JSON array or null if no mappings exist
src/main/java/io/fabric8/maven/docker/access/PortMapping.java