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：
SDKMAN! (The Software Development Kit Manager)
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!