此错误取决于您的建筑结构.将jar文件添加到您的lib文件夹不会做任何事情. 您应该将jar文件添加到类路径中. 如果要通过IDE构建项目，可以说eclipse，则应将其添加到.classpath文件中.如果您使用的是Idea，则应将其添加到您的.iml文件等中. 如果要通过ant构建项目，则应将jar地址添加到build.xml文件中. 我想你不是在使用Maven.

This error is depends on your building structure. Adding jar file to your lib folder is not gonna do anything. You should add the jar file to your classpath. If you are building your project by IDE, lets say eclipse, you should add it to .classpath file. If you are using Idea you should add it to your .iml file and etc. If you are building your project by ant you should add jar address to your build.xml file. I suppose you are not using maven.