为了节省你的时间，请主要看红色字体部分。
前段时间开发项目一切正常，后面将项目拷贝了一份，运行在同一个tomcat上，发现运行时出现了警告信息，项目就无法访问了。
警告信息：
23-Jul-2018 14:08:12.735 警告 [RMI TCP Connection(4)-127.0.0.1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [ROOT] registered the JDBC driver [com.alibaba.druid.mock.MockDriver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
23-Jul-2018 14:08:12.735 警告 [RMI TCP Connection(4)-127.0.0.1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [ROOT] registered the JDBC driver [com.mysql.jdbc.Driver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
23-Jul-2018 14:08:12.735 警告 [RMI TCP Connection(4)-127.0.0.1] org.apache.catalina.loader.WebappClassLoaderBase.clearReferencesJdbc The web application [ROOT] registered the JDBC driver [com.alibaba.druid.proxy.DruidDriver] but failed to unregister it when the web application was stopped. To prevent a memory leak, the JDBC Driver has been forcibly unregistered.
上网查了很多资料，好多都说要重写JBDC注册的方法，也有说换tomcat版本，我都试了没用。另外找了一个方法，就是将数据库驱动包拷贝到tomcat的lib目录中，我刚开始拷贝过去了，也没有解决。
最后看到有人说驱动包最好不要和项目一起打包，突然灵机一动，试着把项目中的数据库驱动maven依赖注释掉，项目就可以运行正常了，真的是坑啊！