code: public static Map<String, String> extractFromPropertiesAsMap(String prefix, Properties properties) {
          Map<String, String> ret = new HashMap<>();
          Enumeration names = properties.propertyNames();
          String prefixP = prefix + ".";
          while (names.hasMoreElements()) {
              String propName = (String) names.nextElement();
              if (propMatchesPrefix(prefixP, propName)) {
                  String mapKey = propName.substring(prefixP.length());
                  if(PROPERTY_COMBINE_POLICY_SUFFIX.equals(mapKey)) {
                      continue;
                  }
  
                  ret.put(mapKey, properties.getProperty(propName));
              }
          }
          return ret.size() > 0 ? ret : null;
      }
docs: Extract part of given properties as a map. The given prefix is used to find the properties,
  the rest of the property name is used as key for the map.
  
  NOTE: If key is "._combine" ({@link #PROPERTY_COMBINE_POLICY_SUFFIX)} it is ignored! This is reserved for combine policy tweaking.
  
  @param prefix prefix which specifies the part which should be extracted as map
  @param properties properties to extract from
  @return the extracted map or null if no such map exists