<reporting> maven-jxr-plugin does not have an explicitly defined <artifactId>. Explicit location elements are good.

                <plugin>
<artifactId>maven-jxr-plugin</artifactId>
<configuration>
<aggregate>true</aggregate>
</configuration>
</plugin>
to

             <plugin>
                <groupId>org.apache.maven.plugins</groupId>
                <artifactId>maven-jxr-plugin</artifactId>
                <configuration>
                    <aggregate>true</aggregate>
                </configuration>
            </plugin>