I guess many e4 developers asked:

How do I restore custom UI-State?

Most likely answer they get is:

Use persistedState of org.eclipse.e4.ui.model.application.MApplicationElement who is a Map<String,String>

What a bad bad idea! This makes your nice UI code who uses dependency inject depend on the e4 application model! What a bad bad idea!

For all users of e4 & JavaFX I’m glad there’s a solution now named org.eclipse.fx.core.Memento who allows you to store simple and complex states without getting a dependency on the e4 framework:

public class MyPart {
  @PostConstruct
  public void init(Memento state) {
    int selectionId = state.get("selectionId",-1);
    ComplexObjectState complexState = state.get("complexObject",null);
  }
 
  @PersistState
  public void saveUIState(Memento state) {
    state.put("selectionId",getSelectionId());
    state.put("complexObject",getComplexObject(),ObjectSerializer.JAXB_SERIALIZER);
  }
}

For more information on the cool stuff you get from e4 & JavaFX visit our wiki.