Prevent Maven generate-sources phase to run twice.

pom.xml

<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/maven-v4_0_0.xsd">
  
  ...
  ...
  ...
  
  <plugins>
    <plugin>
      <artifactId>maven-source-plugin</artifactId>
      <executions>
        <execution>
          <id>attach-sources-no-fork</id>
          <inherited>true</inherited>
          <phase>generate-sources</phase>
          <goals>
            <goal>jar-no-fork</goal>
          </goals>
        </execution>
      </executions>
    </plugin>  
  </plugins>
  
  </project>

Source : http://blog.peterlynch.ca/2010/05/maven-how-to-prevent-generate-sources.html