First, to enable FindBugs reporting in Maven, just add report section to your pom files, something like example below, but of course, you can do your own configuration.

<reporting>
  <plugins>
    <plugin>
      <groupId>org.codehaus.mojo</groupId>
      <artifactId>findbugs-maven-plugin</artifactId>
      <version>2.3</version>
      <configuration>
        <excludeFilterFile>exclude.xml</excludeFilterFile>
        <findbugsXmlOutput>true</findbugsXmlOutput>
        <findbugsXmlWithMessages>true</findbugsXmlWithMessages>
        <threshold>Low</threshold>
        <effort>Max</effort>
        <xmlOutput>true</xmlOutput>
      </configuration>
    </plugin>
  </plugins>
</reporting>

Then you can just use command mvn site if you want to generate more comprehensive project information or mvn findbugs:findbugs for only FindBugs reports.

Finally use mvn dashboard:dashboard to generate charts.

Voila. We have got nice graphic reports.
Well, not so nice. We have bugs we need to fix.