HTTP Status 404 – Not Found Type Status Report Message /WEB-INF/test/hello.jsp Description The origin server did not find a current representation for the target resource or is not willing to disclose that one exists. Apache Tomcat/8.5.32
这里是因为找不到路径才会报出来的错误.因为
因为这里的返回值为null; 返回值为一个jsp的路径就不会报错了..