​
1、报错 failed to transfer from http://0.0.0.0/ during a previous attempt.

com.byd.xxx:xxx-parent:pom:1.1.0-SNAPSHOT failed to transfer from http://0.0.0.0/ during a previous attempt. This failure was cached in the local repository and resolution is not reattempted until the update interval of maven-default-http-blocker has elapsed or updates are forced. Original error: Could not transfer artifact com.byd.xxx:xxx-parent:pom:1.1.0-SNAPSHOT from/to maven-default-http-blocker (http://0.0.0.0/): Blocked mirror for repositories: [xxxrepo (http://hub.byd.com:9081/repository/maven-xxx-snapshot/, default, releases+snapshots), xxx (http://hub.byd.com:9081/repository/maven-xxx-snapshot, default, releases+snapshots)]

Since Maven 3.8.1 http repositories are blocked.

新版本maven 不支持http问题，通过在settings.xml增加如下内容即可解决：

<mirror>
  <id>maven-default-http-blocker</id>
  <mirrorOf>external:http:*</mirrorOf>
  <name>Pseudo repository to mirror external repositories initially using HTTP.</name>
  <url>http://0.0.0.0/</url>
</mirror>

其中url写成实际的地址：例如：http://hub.byd.com:9081/repository/maven-xxx-snapshot/

​2、为什么springboot的pom文件中有的依赖不用加版本号，有的依赖却必须加

应为springboot中引入了一个父依赖，其中包含了一些依赖的版本号，这些依赖不需要添加版本，而有一些依赖并不在父依赖的版本中，这些依赖需要添加版本。