结合MVC，DAO /存储库模式和针对Java GUI应用程序的Swing

Question

I am trying to create a graphical flashcards app from scratch. I have a few questions:

a. I have used Swing to build some apps in the past, calculator app. But I felt that was a trivial application so I want to ramp up my skills as a Java developer.

b. I have been told that a gold standard is to build a small application that uses one of these: MVC, MVM, MVVM and so on.And since I am learning design patterns, I was hoping to use it in the application.

c. My classes are such:

• A model: Flashcard.java(It has a list of answers, a list of pictures, a question), A FlashCard Manager(to perform CRUD)
• Different view classes: GUI interface
• Controller: All the event listeners
• App: To initialize the app

d. I have tried to read online examples of such a combination and what was proposed in for the Manager or DAO, was to have it connect to JDBC for the database. I am trying to simulate that by using a HashMap> for the same purpose.Is that correct or do I have to use JDBC or SQLite?

e. Also am I supposed to have a controller-view pair, that is for every JComponent that uses an event listener or a controller for windows( startup window, main application window, child windows)?

f. Also should the controller class be an interface for all these controllers?

I do not have code because I am still developing it but I just wanted to get a general idea. Thanks for answering my questions.

Answer 1

b. I have been told that a gold standard is to build a small application that uses one of these: MVC, MVM, MVVM and so on.And since I am learning design patterns, I was hoping to use it in the application.

This both right and wrong. Some API's simply don't support the notion of a pure MVC (or variation). Swing for example implements a form of MVC of it's own which is more like M-VC, where the model is separate, but the view and controller are bound.

Think about a JButton . Do you ever apply a controller to it? You can add listeners to it, you can even add listeners directly to it's model, but it has it's own internal control mechanism, which generates events based on keyboard and mouse interaction.

You need to beware of when a MVC might not be suitable or where the amount of work to implement a pure MVC is not worth the effort.

Having said that, you can wrap Swing UI's in another MVC layer, but you need to think about it at a different level. Instead of each controller been considered a "view", you look at the container, which might contain multiple controls and see it as the "view", which a controller then manages.

d. I have tried to read online examples of such a combination and what was proposed in for the Manager or DAO, was to have it connect to JDBC for the database. I am trying to simulate that by using a HashMap> for the same purpose.Is that correct or do I have to use JDBC or SQLite?

This is not an unreasonable idea, however, you want to ensure that the public interface remains constant. This would allow you to change the implementation at a later date to use JDBC or a web service without having to rewrite the code that depends on it

e. Also am I supposed to have a controller-view pair, that is for every JComponent that uses an event listener or a controller for windows( startup window, main application window, child windows)?

This will depend. I tend to avoid exposing individual components, as this exposes them to unwanted modifications (you may not want a controller to be able to change the text of a button for example)

As a general rule of thumb, I try to make the relationship between the controller and the view as vanilla as possible, meaning that the controller shouldn't care about how the view is implemented, only that it upholds the contract between the it subscribes to.

This generally means I have a functional view, which is contracted to produce certain events/data and allows certain interaction (from the controller)

f. Also should the controller class be an interface for all these controllers?

IMHO, yes. This allows a view/controller/model to be implemented differently, but allows the rest of the code to continue working with it without the need to be modified.

The bottom line is, implementing a MVC over Swing is not as simple as people think it is. It takes some planning and consideration, but it is doable.

For a more detailed example, have a look at Java and GUI - Where do ActionListeners belong according to MVC pattern?