maven-site plugins 3.3 java.lang.ClassNotFoundException: org.apache.maven.doxia.siterenderer.DocumentContent

I had just started to get this issue also during builds. What worked for me was to specifically define the maven-site-plugin and the maven-project-info-reports-plugin along with the version numbers in the pom.

<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-site-plugin</artifactId>
  <version>3.7.1</version>
</plugin>
<plugin>
  <groupId>org.apache.maven.plugins</groupId>
  <artifactId>maven-project-info-reports-plugin</artifactId>
  <version>3.0.0</version>
</plugin>

This is caused by maven-project-info-reports-plugin updated to 3.0.0, and rely on doxia-site-renderer 1.8 (and have org.apache.maven.doxia.siterenderer.DocumentContent this class), but maven-site-plugin:3.3 rely on doxia-site-renderer:1.4 (and do not have org.apache.maven.doxia.siterenderer.DocumentContent)

We can specific maven-project-info-reports-plugin version in reporting part:

<reporting>
        <plugins>           
            <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-project-info-reports-plugin</artifactId>
                <version>2.9</version>
            </plugin>           
        </plugins>    
    </reporting>

Or we can specify maven-site-plugin to the latest 3.7.1 like:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-site-plugin</artifactId>
    <version>3.7.1</version>
</plugin>

in build part of pom

Version of the maven site plugin needs to be explicitly set in the build section too. Here is the example:

<reporting>
    <plugins>
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-project-info-reports-plugin</artifactId>
            <version>3.0.0</version>
            <reportSets>
                <reportSet>
                    <reports>
                        <report>index</report>
                        <report>licenses</report>
                        <report>dependency-info</report>
                    </reports>
                </reportSet>
            </reportSets>
        </plugin>
    </plugins>
</reporting>

<build>
    <plugins>
        <!-- Part of Maven - specified version explicitly for compatibility
             with the maven-project-info-reports-plugin 3.0.0-->
        <plugin>
            <groupId>org.apache.maven.plugins</groupId>
            <artifactId>maven-site-plugin</artifactId>
            <version>3.7.1</version>
        </plugin>
    </plugins>
</build>