spring boot 引入fastjson，com.alibaba.fastjson不存在（Springboot-测试项目）
先解决最初的的包不找到问题，适用所有包找不到跟进。
<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><id>nexus-aliyun</id><name>Nexus aliyun</name><url>https://maven.aliyun.com/nexus/content/groups/public/</url><mirrorOf>central</mirrorOf></mirror></mirrors>