Could not transfer artifact *************** from/to central (http://repo1.maven.org/maven2

問題：

Could not transfer artifact *************** from/to central (http://repo1.maven.org/maven2): Connection to http://repo1.maven.org refused: Connection timed out: connect -> [Help 1]

解決方法：

Configuring a proxy

You can configure a proxy to use for some or all of your HTTP requests with Maven. The username and password are only required if your proxy requires basic authentication (note that later releases may support storing your passwords in a secured keystore - in the mean time, please ensure your settings.xml file (usually ${user.home}/.m2/settings.xml) is secured with permissions appropriate for your operating system).

The nonProxyHosts setting accepts wild cards, and each host not to proxy is separated by the | character. This matches the JDK configuration equivalent.

<settings>
  <proxies>
   <proxy>
      <id>example-proxy</id>
      <active>true</active>
      <protocol>http</protocol>
      <host>proxy.example.com</host>
      <port>8080</port>
      <username>proxyuser</username>
      <password>somepassword</password>
      <nonProxyHosts>www.google.com|*.example.com</nonProxyHosts>
    </proxy>
  </proxies>
</settings>