第一次用 Spring Starter Project 创建一个Spring应用时，POM 文件报错：
Project build error: Non-resolvable parent POM for com.example:demo-1:0.0.1-SNAPSHOT: Failure to transfer org.springframework.boot:spring-boot-starter-parent:pom:1.5.4.RELEASE from https://repo.maven.apache.org/maven2 was cached in the local repository, resolution will not be reattempted until the update interval of central has elapsed or updates are forced. Original error: Could not transfer artifact org.springframework.boot:spring-boot-starter-parent:pom:1.5.4.RELEASE from/to central (https://repo.maven.apache.org/maven2): repo.maven.apache.org: nodename nor servname provided, or not known and 'parent.relativePath' points at no local POM
解决方法：
参考stack overflow：
I've also encountered a lot of error when creating a new STS project for the first time. This seems to be happen only if I don't have any Maven repository or haven't launch/use Maven before. In my case, I solve this by launching Maven command from command line manually. Try to 'cd' to the project directory that contains pom.xml and call mvn that comes with STS from there.
cd c:\users\name\sts-projects\projectname
c:\programs\springsource\apache-maven-3.0.3\bin\mvn compile
Then, open STS, right click on project name, select 'Maven', 'Update Project...' Select on 'Force Update of Snapshots/Releases'. Don't select 'Offline'.
即打开终端，进入出错项目的根目录，然后使用 maven bin 目录下的 mvn 编译一下，完成之后右键项目 Maven——Update Project 即可。