方法1、下载了所有POM里的依赖包的source
mvn dependency:resolve -Dclassifier=sources
方法2、下载指定依赖包(artifactId)的source
mvn dependency:sources -DincludeArtifactIds=spring-webmvc
mvn dependency:resolve -Dclassifier=sources
mvn dependency:sources -DincludeArtifactIds=spring-webmvc