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

This error occurs when the org.apache.catalina.users.MemoryUserDatabaseFactory class is not found in the classpath. This class is part of the Tomcat Users component and is used to create a user database in memory.

To resolve this issue, make sure that the tomcat-users.jar file is included in your project's classpath. This file can be found in the Tomcat installation directory under the lib folder.

Alternatively, if you are using a build tool such as Maven or Gradle, you can add the following dependency to your project's build file:

Maven:

<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat-users</artifactId>
    <version>${tomcat.version}</version>
</dependency>

Gradle:

dependencies {
    compile 'org.apache.tomcat:tomcat-users:${tomcat.version}'
}

Note: Replace ${tomcat.version} with the version of Tomcat you are using.