参考博客：https://blog.csdn.net/Leo_libin/article/details/84101663
访问controller地址时，显示错误页面，报错如下：
1 Whitelabel Error Page 2 This application has no explicit mapping for /error, so you are seeing this as a fallback. 3 4 Tue Aug 25 15:24:46 CST 2020 5 There was an unexpected error (type=Not Found, status=404).
将启动页放在根目录下即可，根目录指的是在创建项目时Group所指定的目录
在pom.xml中也可找到
重启项目，页面就可以访问成功了。