错误不是找不到类。由于Web应用程序已停止，因此无法加载。我怀疑在重新启动Web应用程序之后可能会发生这种情况，它会在短时间内停止运行。然后代码中的一些 finalize（）方法可能试图进行一些清理太晚了。无论你的代码还是MySQL驱动程序，我都不能说。你肯定一次只能在一个目录中有一个jar版本。您可能希望将其升级到最新（现在为5.1.15）以防万一已经修复的东西可能会影响你。

The error is not that the class can't be found. It's not being allowed to load because the web application has been stopped. I suspect this might be happening after the web application is restarted, where it's down for a short period of time. Then some finalize() method in the code is probably trying to do some cleanup too late. Whether or not that's in your code or the MySQL driver I can't say. You definitely should only have one version of a jar in a directory at a time. You might want to upgrade it to the latest (5.1.15 right now) in case something has been fixed that might be affecting you.