使用idea 下载源码出现：Sources not found for:
解决方案：在对应的pom.xml 文件中打开 terminal，执行 mvn命令：
mvn dependency:sources
mvn dependency:resolve -Dclassifier=javadoc
[INFO] Finished at: 2020-07-02T20:07:39+08:00
[INFO] ------------------------------------------------------------------------
D:\IdeaWorkSpace\biyao\appapi>mvn dependency:sources