title: JavaFX - creating custom dialogs using fxml
body: <p>I'm new in javafx and I was trying to create custom dialogs/alerts. The thing is that I'm using Scene Builder to design the GUI, and I want to modify the dialog each time I load the fxml file (i.e change the title, label text, etc.), so I wanted to know if there's a way to send parameters and modify the stage/scene, or any other way I can achieve this. </p>
  
  <p>To be more specific, let's say there's an error I want to handle anywhere in my program, so I load a new fxml file that represents the error dialog I created, and I modify the components inside it, depending on the type of error I need to handle, similar to, for example, JOptionPane.showMessageDialog(...) in swing.</p>