java.lang.NoClassDefFoundError:

这个错误，网上找了好多解决办法，都不正确，最后在Stack Overflow找到了原因：

原文地址：http://stackoverflow.com/questions/30302612/tomcat-java-lang-noclassdeffounderror-could-not-initialize-class

重点是下面这句话：
If an exception is propagating out of the constructor of the class or a static initializer, then you also get java.lang.NoClassDefFoundError: Could not initialize class ...