先贴一下Maven官网关于settings.xml配置文件的使用说明：
There are two locations where a settings.xml file may live:
- The Maven install: ${maven.home}/conf/settings.xml
- A user’s install: ${user.home}/.m2/settings.xml
The former settings.xml are also called global settings, the latter settings.xml are referred to as user settings. If both files exists, their contents gets merged, with the user-specific settings.xml being dominant.
Tip: If you need to create user-specific settings from scratch, it’s easiest to copy the global settings from your Maven installation to your ${user.home}/.m2 directory. Maven’s default settings.xml is a template with comments and examples so you can quickly tweak it to match your needs.
Maven安装目录的settings.xml，是提供作为模版供用户使用的
Maven安装目录的settings.xml，是全局级别的配置
用户指定的settings.xml，是用户级别的配置
如果这两个级别的配置文件，都做了配置。Maven会把两个配置文件的配置内容合并，并以优先使用用户级别的配置。
日常使用Maven时，全局配置---Maven安装目录的settings.xml，建议不要做具体配置，按照maven官方文档传达的精神，当作模版使用。使用用户级别的配置文件做配置就好了。