java.lang.ClassNotFoundException: org.apache.catalina.users. MemoryUserDatabaseFactory

This error indicates that the class org.apache.catalina.users.MemoryUserDatabaseFactory cannot be found by the Java Virtual Machine (JVM) during runtime. This class is part of the Apache Tomcat server, and is used to create an in-memory user database for authentication purposes.

To resolve this error, you need to make sure that the required Tomcat libraries are included in your project's classpath. If you are using a build tool such as Maven or Gradle, you can add the Tomcat dependencies to your project's pom.xml or build.gradle file respectively.

Alternatively, you can manually add the required Tomcat libraries to your project's classpath. You can download the Tomcat binaries from the Apache Tomcat website and extract the necessary JAR files into your project's lib directory.

Once you have added the required Tomcat libraries to your project's classpath, you should be able to run your application without encountering the ClassNotFoundException.