Hi @tobiasdiez I understand the situation and I do agree with you about the other PR being more suitable.

However, you were on the right track and we should use the power of JavaFX bindings instead of the old-style update mechanism. For validation there is a framework https://github.com/sialcasa/mvvmFX/wiki/Validation which allows to implement this kind of logic in a clean way. May I ask you to rework the code completely using this framework? If you are not in the mood to do this and prefer to work on something else, I would perfectly understand this.

I would like to work on this. Could you tell me exactly what all I will have to re-implement?
I will make a different PR for all the changes to GroupDIalog and close this one.

Thank you for updating me about the situation and for the guidance. I look forward to keep contributing to JabRef.

Thanks for your understanding.

As of now the data in the group dialog is validated in the updateComponents method. Instead it is better to have a collection of validation rules that are then combined in a so-called composite validation rule. This composition rule can then be used to control the disable status of the save button.

You can find this strategy live for example here:

• Define rules:
  

  jabref/src/main/java/org/jabref/gui/shared/SharedDatabaseLoginDialogViewModel.java

  Lines 98 to 103 in 5479070

  	databaseValidator = new FunctionBasedValidator<>(database, notEmpty, ValidationMessage.error(Localization.lang("Required field \"%0\" is empty.", Localization.lang("Library"))));
  	hostValidator = new FunctionBasedValidator<>(host, notEmpty, ValidationMessage.error(Localization.lang("Required field \"%0\" is empty.", Localization.lang("Port"))));
  	portValidator = new FunctionBasedValidator<>(port, notEmpty, ValidationMessage.error(Localization.lang("Required field \"%0\" is empty.", Localization.lang("Host"))));
  	userValidator = new FunctionBasedValidator<>(user, notEmpty, ValidationMessage.error(Localization.lang("Required field \"%0\" is empty.", Localization.lang("User"))));
  	folderValidator = new FunctionBasedValidator<>(folder, notEmptyAndfilesExist, ValidationMessage.error(Localization.lang("Please enter a valid file path.")));
  	keystoreValidator = new FunctionBasedValidator<>(keystore, notEmptyAndfilesExist, ValidationMessage.error(Localization.lang("Please enter a valid file path.")));

• Combine them:
  

  jabref/src/main/java/org/jabref/gui/shared/SharedDatabaseLoginDialogViewModel.java

  Lines 105 to 106 in 5479070

  	formValidator = new CompositeValidator();
  	formValidator.addValidators(databaseValidator, hostValidator, portValidator, userValidator);

• Bind to button:
  

  jabref/src/main/java/org/jabref/gui/shared/SharedDatabaseLoginDialogView.java

  Line 64 in 544a2d5

  btnConnect.disableProperty().bind(viewModel.formValidation().validProperty().not());

• Moreover, it is easy to display a notification to the user in case the data is invalid:
  

  jabref/src/main/java/org/jabref/gui/shared/SharedDatabaseLoginDialogView.java

  Lines 105 to 108 in 544a2d5

  	visualizer.initVisualization(viewModel.dbValidation(), database, true);
  	visualizer.initVisualization(viewModel.hostValidation(), host, true);
  	visualizer.initVisualization(viewModel.portValidation(), port, true);
  	visualizer.initVisualization(viewModel.userValidation(), user, true);