code: public void init() {
          // load the configuration file
          String darConfigurationFileLocation = getDarConfigurationFileLocation();
          if (log.isDebugEnabled()) {
              log.debug("Default Application Router file Location : " + darConfigurationFileLocation);
          }
          File darConfigurationFile = null;
          // hack to get around space char in path see http://weblogs.java.net/blog/kohsuke/archive/2007/04/how_to_convert.html,
          // we create a URL since it's permissive enough
          URL url = null;
          try {
              url = new URL(darConfigurationFileLocation);
          } catch (MalformedURLException e) {
              log.fatal("Cannot find the default application router file ! ", e);
              throw new IllegalArgumentException("The Default Application Router file Location : " + darConfigurationFileLocation
                      + " is not valid ! ", e);
          }
          try {
              darConfigurationFile = new File(new URI(darConfigurationFileLocation));
          } catch (URISyntaxException e) {
              // if the uri contains space this will fail, so getting the path will work
              darConfigurationFile = new File(url.getPath());
          }
          FileInputStream fis = null;
          try {
              fis = new FileInputStream(darConfigurationFile);
              properties.load(fis);
          } catch (FileNotFoundException e) {
              log.fatal("Cannot find the default application router file ! ", e);
              throw new IllegalArgumentException("The Default Application Router file Location : " + darConfigurationFileLocation
                      + " is not valid ! ", e);
          } catch (IOException e) {
              log.fatal("Cannot load the default application router file ! ", e);
              throw new IllegalArgumentException("The Default Application Router file Location : " + darConfigurationFileLocation
                      + " cannot be loaded ! ", e);
          } finally {
              if (fis != null) {
                  try {
                      fis.close();
                  } catch (IOException e) {
                      log.error("fail to close the following file " + darConfigurationFile.getAbsolutePath(), e);
                  }
              }
          }
      }
docs: Load the configuration file as defined in JSR289 Appendix C ie as a system property "javax.servlet.sip.dar"
  
  @throws IllegalArgumentException if anything goes wrong when trying to load the configuration file