For artifact {javax.servlet:javax.servlet-api:null:jar}: The version cannot be empty.

This error message indicates that you are trying to use a Java Servlet API artifact with an empty version number. The version number is a required attribute for all Maven artifacts, including the Servlet API.

To resolve this error, you need to specify a valid version number for the javax.servlet:javax.servlet-api artifact in your project's dependencies section. You can find the latest version of the Servlet API on Maven Central repository, and add it to your project's pom.xml file.

For example, if you want to use version 4.0.1 of the Servlet API, you can add the following dependency to your pom.xml file:

<dependency>
  <groupId>javax.servlet</groupId>
  <artifactId>javax.servlet-api</artifactId>
  <version>4.0.1</version>
</dependency>

Make sure to update the version number according to your needs and the latest available version.