Having findbug running against generated code is a problem because you'll have so many pointless warnings and errors that you might miss the real ones. The ones you can really do something about.

To exclude a package from the repports you'll have to create a exclution filter file usualy name findbugs-exclude.xml
<FindBugsFilter>
<Match>
<Package name="~org.sinarf.myapp.mygeneratedpackage.*" />
</Match>
</FindBugsFilter>

Filter documentation should contain anything you would need : Chapter 8. Filter Files.

Maven should be informed that it should use a filter exclude file.
<reporting>
<plugins>
<plugin>
<groupId>org.codehaus.mojo</groupId>
<artifactId>findbugs-maven-plugin</artifactId>
<configuration>
<findbugsXmlOutput>true</findbugsXmlOutput>
<findbugsXmlWithMessages>true</findbugsXmlWithMessages>
<excludeFilterFile>findbugs-exclude.xml</excludeFilterFile>
</configuration>
</plugin>
</plugins>
</reporting>