Maven项目报错：Cannot access nexus-aliyun (http://maven.aliyun.com/nexus/content/...) in offline mode

Maven项目使用idea打开后，无论如何都无法导入pom里面的依赖，点击reimport就瞬间结束。

 
然后，install项目会报以下错误，很是奇葩。
 
即：

[ERROR] Plugin org.apache.maven.plugins:maven-install-plugin:2.4 or one of its dependencies could not be resolved: Cannot access nexus-aliyun (http://maven.aliyun.com/nexus/content/groups/public) in offline mode and the artifact org.apache.maven.plugins:maven-install-plugin:jar:2.4 has not been downloaded from it before. -> [Help 1]

报错清晰说明了，是因为依赖都无法下载。而导致依赖无法下载的原因，是因为项目被设置为offline mode。因为项目是拷贝过来的，所以，不知道之前是怎么回事，真是很坑。

知道问题原因，解决办法，就是设置maven配置取消offline mode.
File-》Settings-》Build,Execution,Deployment-》Build Tools-》Maven-》取消Work offline

1.https://blog.csdn.net/doudou0809/article/details/80345789
 

com http: HTTP Maven IN nexus access content