[integration] Failed to execute goal org.codehaus.mojo:exec-maven-plugin:1.2:java (default-cli)

To solve this problem in IntelliJ...
1) Put your .fxml files into resources directory
2) In the Start method define the path to .fxml file in the following way:
Parent root = FXMLLoader.load(getClass().getResource("/sample.fxml"));
The / seemed to solve this problem for me :)