Could not transfer artifact mysql:mysql-connector-java:pom:unknown from/to central

This error message usually occurs when Maven is unable to download an artifact from the central repository due to network connectivity issues or server problems.

You can try the following steps to resolve this issue:

1. Check your internet connection and make sure it is stable.
2. Clear your local Maven repository and try downloading the artifact again. You can do this by deleting the contents of the ".m2/repository" folder in your home directory.
3. Check if the artifact exists in any other repositories that you have configured in your project's pom.xml file.
4. If none of the above steps work, you can try adding the central repository to your project's pom.xml file explicitly:

<repositories>
  <repository>
    <id>central</id>
    <url>https://repo.maven.apache.org/maven2</url>
  </repository>
</repositories>

This will ensure that Maven always tries to download artifacts from the central repository.