一、原因
IntelliJ IDEA期待一个the standard Groovy SDK
二、解决方案：
下载安装Groovy就可以了
官网下载地址：
通过包管理工具下载Groovy：
This tool makes installing Groovy on any Bash platform (Mac OSX, Linux, Cygwin, Solaris or FreeBSD) very easy.
Simply open a new terminal and enter:
$ curl -s get.sdkman.io | bash
Follow the instructions on-screen to complete installation.
Open a new terminal or type the command:
$ source "$HOME/.sdkman/bin/sdkman-init.sh"
Then install the latest stable Groovy:
$ sdk install groovy
After installation is complete and you've made it your default version, test it with:
$ groovy -version
That's all there is to it!