項目啟動正常，hello也能訪問，dao測試也成功，但是最后頁面訪問Controller報500，查看路徑也沒錯控制臺報錯2019-03-20 20:01:03.650 ERROR 11652 --- [nio-8080-exec-1] o.a.c.c.C.[.[.[.[dispatcherServlet]? ? ? : Servlet.service() for servlet [dispatcherServlet] in context with path [/demo] threw exception [Request processing failed; nested exception is java.lang.NullPointerException] with root causejava.lang.NullPointerException: null at com.imooc.demo.web.AreaController.getAreaById(AreaController.java:52) ~[classes/:na]