private File getCacheXmlFile() {
    String cacheXmlFileName = getCacheXmlFileName();
    File cacheXmlFile = new File(cacheXmlFileName);
    // If the cache xml file is not absolute, point it at the conf directory.
    if (!cacheXmlFile.isAbsolute()) {
      if (System.getProperty("catalina.base") != null) {
        cacheXmlFile = new File(System.getProperty("catalina.base") + "/conf/", cacheXmlFileName);
      }
    }
    return cacheXmlFile;
  }
Instance reference which is set in static initialization blocks of any subclasses.
extensions/geode-modules/src/main/java/org/apache/geode/modules/session/bootstrap/AbstractCache.java