private String extractPortPropertyName(String name) {
        String mavenPropName = EnvUtil.extractMavenPropertyName(name);
        return mavenPropName != null ? mavenPropName : 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