code: public static void registerAccessor(Class<?> documentType, DocumentAccessor accessor) {
  		Assert.notNull(documentType, "documentType may not be null");
  		Assert.notNull(accessor, "accessor may not be null");
  		if (accessors.containsKey(documentType)) {
  			DocumentAccessor existing = getAccessor(documentType);
  			LOG.warn(String.format("DocumentAccessor for class %s already exists: %s will be overridden by %s", documentType, existing.getClass(), accessor.getClass()));
  		}
  		putAccessor(documentType, accessor);
  		LOG.debug("Registered document accessor: {} for class: {}", accessor.getClass(), documentType);
  	}
docs: Used to register a custom DocumentAccessor for a particular class.
  Any existing accessor for the class will be overridden.
  @param documentType
  @param accessor