1. 错误信息：

在cmd内查看Maven能不能正常使用。
输入命令：mvn help:system

[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  23.239 s
[INFO] Finished at: 2019-04-11T19:12:21+08:00
[INFO] ------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-help-plugin:3.1.1:system (default-cli) on project standalone-pom: Execution default-cli of goal org.apache.maven.plugins:maven-help-plugin:3.1.1:system failed: Plugin org.apache.maven.plugins:maven-help-plugin:3.1.1 or one of its dependencies could not be resolved: Could not transfer artifact org.codehaus.plexus:plexus-component-annotations:jar:1.7.1 from/to central (https://repo.maven.apache.org/maven2): Connect to repo.maven.apache.org:443 [repo.maven.apache.org/151.101.196.215] failed: Connection timed out: connect -> [Help 1]
[ERROR]
[ERROR] To see the full stack trace of the errors, re-run Maven with the -e switch.
[ERROR] Re-run Maven using the -X switch to enable full debug logging.
[ERROR]
[ERROR] For more information about the errors and possible solutions, please read the following articles:
[ERROR] [Help 1] http://cwiki.apache.org/confluence/display/MAVEN/PluginResolutionException

   
   

   
   
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2. 解决方案

最后经过排查，发现用的默认国外服务器的问题，改为aliyun的后，问题解决。
方法如下：
修改Maven的settings.xml文件，在mirrors标签内添加：

	<mirror>
  	    <id>nexus-aliyun</id>
  		<mirrorOf>*</mirrorOf>
  		<name>Nexus aliyun</name>
  		<url>http://maven.aliyun.com/nexus/content/groups/public</url>
  	</mirror>

   
   

   
   
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最后终于看到了SUCCESS。
这样构建JavaWeb项目也没了问题。