maven conf/settings.xml配置多个镜像地址防止部分项目无法拉取：

  <mirrors>
    <!-- mirror
     | Specifies a repository mirror site to use instead of a given repository. The repository that
     | this mirror serves has an ID that matches the mirrorOf element of this mirror. IDs are used
     | for inheritance and direct lookup purposes, and must be unique across the set of mirrors.
     |
    <mirror>
      <id>mirrorId</id>
      <mirrorOf>repositoryId</mirrorOf>
      <name>Human Readable Name for this Mirror.</name>
      <url>http://my.repository.com/repo/path</url>
    </mirror>
     -->

    <mirror>
        <!--This sends everything else to /public -->
        <id>nexus-aliyun</id>
        <mirrorOf>*</mirrorOf>
        <name>Nexus aliyun</name>
        <url>http://maven.aliyun.com/nexus/content/groups/public</url>
    </mirror>

    <mirror>
        <id>osc</id>
        <mirrorOf>*</mirrorOf>
        <url>http://maven.oschina.net/content/groups/public/</url>
    </mirror>

    <mirror>    
      <id>repo2</id>    
      <mirrorOf>central</mirrorOf>    
      <name>Human Readable Name for this Mirror.</name>    
      <url>http://repo2.maven.org/maven2/</url>    
    </mirror>    

    <mirror>    
      <id>net-cn</id>    
      <mirrorOf>central</mirrorOf>    
      <name>Human Readable Name for this Mirror.</name>    
      <url>http://maven.net.cn/content/groups/public/</url>     
    </mirror>    

    <mirror>    
      <id>ui</id>    
      <mirrorOf>central</mirrorOf>    
      <name>Human Readable Name for this Mirror.</name>    
      <url>http://uk.maven.org/maven2/</url>    
    </mirror>    

    <mirror>    
      <id>ibiblio</id>    
      <mirrorOf>central</mirrorOf>    
      <name>Human Readable Name for this Mirror.</name>    
      <url>http://mirrors.ibiblio.org/pub/mirrors/maven2/</url>    
    </mirror>    

    <mirror>    
      <id>jboss-public-repository-group</id>    
      <mirrorOf>central</mirrorOf>    
      <name>JBoss Public Repository Group</name>    
      <url>http://repository.jboss.org/nexus/content/groups/public</url>    
    </mirror>  

    <mirror>    
      <id>JBossJBPM</id>  
      <mirrorOf>central</mirrorOf> 
      <name>JBossJBPM Repository</name>   
      <url>https://repository.jboss.org/nexus/content/repositories/releases/</url>  
    </mirror>