1. Jar package is not imported
2 Multiple versions conflict
3 Version mismatch between idea and Tomcat

java.lang.ClassNotFoundException: com.mysql.cj.jdbc.Driver
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1444)
	at org.apache.catalina.loader.WebappClassLoaderBase.loadClass(WebappClassLoaderBase.java:1252)

Error reporting check

1. Check whether you have introduced MySQL-connector-Java.Jar package

This is used to link the database

2. Check the position of the bag

be sure to check

3. See if there are more spaces in the incoming string