private String extractHostPropertyName(String name) {
        if (name.startsWith("+")) {
            return name.substring(1);
        } else {
            return EnvUtil.extractMavenPropertyName(name);
        }
    }
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