How to reference javadocs to dependencies in Maven’s eclipse plugin when javadoc not attached to dependency

From the Maven Eclipse Plugin FAQ

The following example shows how to do
this in the command-line:

mvn eclipse:eclipse -DdownloadSources=true  -DdownloadJavadocs=true 

or in your pom.xml:

<project>
  [...]
  <build>
    [...]
    <plugins>
      [...]
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-eclipse-plugin</artifactId>
        <configuration>
          <downloadSources>true</downloadSources>
          <downloadJavadocs>true</downloadJavadocs>
        </configuration>
      </plugin>
      [...]
    </plugins>
    [...]
  </build>
  [...]
</project>