无法加载主类 org.apache.maven.wrapper.MavenWrapperMain

目前SpringBoot项目需要用的mvnw来进行相关操作，但是有时候会出现如下错误：

/Users/liyang/TestProjects/springcloud
错误: 找不到或无法加载主类 org.apache.maven.wrapper.MavenWrapperMain

这个错误的原因就是MavenWrapperMain不存在，那么我们需要再安装一次这个类即可。但是每次升级maven都需要重复这个操作。

mvn -N io.takari:maven:wrapper

mvn -N io.takari:maven:wrapper
[INFO] Scanning for projects...
[INFO]
[INFO] ------------------< org.apache.maven:standalone-pom >-------------------
[INFO] Building Maven Stub Project (No POM) 1
[INFO] --------------------------------[ pom ]---------------------------------
[INFO]
[INFO] --- maven:0.5.0:wrapper (default-cli) @ standalone-pom ---
[INFO]
[INFO] The Maven Wrapper version 0.3.0 has been successfully setup for your project.
[INFO] Using Apache Maven 3.5.2
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 0.452 s
[INFO] Finished at: 2018-05-02T15:42:00+08:00
[INFO] ------------------------------------------------------------------------