加上aliyun的镜像地址，我的maven setting.xml 里完整镜像地址如下：
<mirrors>
<mirror>
<id>alimaven</id>
<name>aliyun maven</name>
<url>http://maven.aliyun.com/nexus/content/groups/public/</url>
<mirrorOf>central</mirrorOf>
</mirror>
<mirror>
<id>spring-snapshots</id>
<name>Spring Snapshots</name>
<url>https://repo.spring.io/snapshot</url>
<mirrorOf>central</mirrorOf>
</mirror>
<mirror>
<id>spring-milestones</id>
<name>Spring Milestones</name>
<url>https://repo.spring.io/milestone</url>
<mirrorOf>central</mirrorOf>
</mirror>
</mirrors>
end.