能下载到源代码的原则是仓库中打了resource的jar包

1.使用命令

  mvn dependency:sources 下载依赖包的源代码。

  mvn dependency:sources -DdownloadSources=true -DdownloadJavadocs=true

  mvn org.apache.maven.plugins:maven-dependency-plugin:2.8:get -Dartifact=javax.mail:mail:1.1:jar:sources

2.eclipse窗口

  eclipse窗口->首选项->maven->勾选download artifact sources

  eclipse的项目maven dependecies中选择对应的jar,右击->maven->download sources

3.在pom中设置插件

  <plugin>
     <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-eclipse-plugin</artifactId>
     <version>2.9</version>
     <configuration>
              <downloadSources>true</downloadSources>
              <downloadJavadocs>true</downloadJavadocs>
          </configuration>
  </plugin>