code: static String readMapping(String root, String index) throws IOException {
  		if (root == null) {
  			return readMapping(index);
  		}
  		String mappingFile = root + "/" + index + "/_doc" + Defaults.JsonFileExtension;
  		return readFileFromClasspath(mappingFile);
  	}
docs: Read a mapping from index/_doc.json file
  @param root dir within the classpath
  @param index index name
  @return The mapping
  @throws IOException if the connection with elasticsearch is failing