@Override public boolean deleteBook(Book book) { Document original = __wrapper.getDocument(); Document doc = __wrapper.getDocument(); try { doc = __wrapper.deleteEntry(doc, "isbn", book.getIsbn()); if (doc == null) { return false; } else { __wrapper.commit(doc); return true; } } catch (Exception e) { e.printStackTrace(); __wrapper.rollback(original); return false; } }