code: private void copyPropertiesOverParameters(Map<String, String> parameters) {
          Properties properties = System.getProperties();
          for (Object object : properties.keySet()) {
              String key = (String) object;
              if (key.startsWith(SYSTEM_PROPERTY_PREFIX)) {
                  parameters.put(key.substring(SYSTEM_PROPERTY_PREFIX.length()),
                                 properties.getProperty(key));
              }
          }
      }
docs: Augment, and perhaps override, the server parameters, using any System
  Property whose name begins with "fedora.journal.". So, for example, a
  System Property of "fedora.journal.mode" will override a server parameter
  of "mode".