Concrete Code Example of MVP [closed]

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• Model - some kind of value object (VO)
• View - represents or generates the UI
• Presenters - business logic

@platzhirsch Quickly skimmed through that (will read through it with more thought) but I just have to point out that his MVC solution is incorrect, Controller should have actions such as "get customer's orders" while "load|save customer" is a responsibility of the Model. Maybe it's just my head but for me MVP looks like MVVM which really is just another variation of MVC. gah, I hope someone would make a broad comparison of all these MVwhatevers, just like with anyDD:s.

@Esko - I'm no expert but have been out of school for about 3 years now and I'm beginning to realize that a lot of "theoretical" stuff we all learned in our Software Engineering I class is just that. *theoretical*! These PhD's are smart and are great (in fact, its how they make their living!) at pitching 3-letter acronymed patterns in their white papers, but as we see with MVC, MVP, MVVM and who knows what else. when you lift the veil, its all just "Emperor's New Clothes." I bet you MVC/MVP/MVVM all first appear in some PhD's doctoral dissertation. they sound great, but form over substance.

1 Answer 1

MVP is my favorite design pattern to create a UI.

The big difference between MVP and MVC is how to handle the view.

• In MVC, the Controller manipulates the view, taking care of how to render in the view parts of the user actions and model. That means that the Controller and View have 'tight coupling'.
• In MVP, the Presenter takes care of the user tasks, the model is shared between the Presenter and View. So the view renders UI according to the model, sometimes the view can have actions to be called from the Presenter. The Presenter and View can have a defined interface contracts to make them 'loose coupling'. For example you can create a View for Java Swing UI and another for JavaFX UI. Or if the connection to the data source changes, then you just need update the presenter.

There are many styles to program the MVP.

In a formal way, consists in create interfaces for each element of the design pattern.

/*-- file: Application.java --*/ import javax.swing.JOptionPane; /** * * @author danLeon */ interface LoginModel < String getUser(); void setUser(String user); >class MyLoginModel implements LoginModel < String user; @Override public String getUser() < return user; >@Override public void setUser(String user) < this.user = user; >> interface LoginView < LoginPresenter getPresenter(); void setPresenter(LoginPresenter loginPresenter); void updateModelFromView(); void updateViewFromModel(); void open(); void close(); void userRejected(); >class MyLoginView extends javax.swing.JFrame implements LoginView < private LoginPresenter loginPresenter; /** * Creates new form MyLoginView */ public MyLoginView() < initComponents(); >@SuppressWarnings("unchecked") private void initComponents() < java.awt.GridBagConstraints gridBagConstraints; jLabel1 = new javax.swing.JLabel(); jTextField1 = new javax.swing.JTextField(); jLabel2 = new javax.swing.JLabel(); jButton1 = new javax.swing.JButton(); setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE); setBounds(new java.awt.Rectangle(0, 0, 0, 0)); java.awt.GridBagLayout layout = new java.awt.GridBagLayout(); layout.columnWidths = new int[] ; layout.rowHeights = new int[] ; getContentPane().setLayout(layout); jLabel1.setFont(new java.awt.Font("Tahoma", 1, 11)); // NOI18N jLabel1.setText("Welcome"); gridBagConstraints = new java.awt.GridBagConstraints(); gridBagConstraints.gridx = 0; gridBagConstraints.gridy = 0; gridBagConstraints.gridwidth = 3; getContentPane().add(jLabel1, gridBagConstraints); jTextField1.setColumns(13); gridBagConstraints = new java.awt.GridBagConstraints(); gridBagConstraints.gridx = 2; gridBagConstraints.gridy = 2; gridBagConstraints.fill = java.awt.GridBagConstraints.HORIZONTAL; getContentPane().add(jTextField1, gridBagConstraints); jLabel2.setText("User"); gridBagConstraints = new java.awt.GridBagConstraints(); gridBagConstraints.gridx = 0; gridBagConstraints.gridy = 2; getContentPane().add(jLabel2, gridBagConstraints); jButton1.setText("Login"); jButton1.addActionListener(new java.awt.event.ActionListener() < public void actionPerformed(java.awt.event.ActionEvent evt) < jButton1ActionPerformed(evt); >>); gridBagConstraints = new java.awt.GridBagConstraints(); gridBagConstraints.gridx = 2; gridBagConstraints.gridy = 4; getContentPane().add(jButton1, gridBagConstraints); pack(); > private void jButton1ActionPerformed(java.awt.event.ActionEvent evt) < getPresenter().login(); >private javax.swing.JButton jButton1; private javax.swing.JLabel jLabel1; private javax.swing.JLabel jLabel2; private javax.swing.JTextField jTextField1; @Override public void updateModelFromView() < getPresenter().getModel().setUser(jTextField1.getText()); >@Override public void updateViewFromModel() < jTextField1.setText(getPresenter().getModel().getUser()); >@Override public void open() < setVisible(true); jTextField1.selectAll(); jTextField1.requestFocus(); >@Override public void close() < dispose(); >@Override public void userRejected() < jLabel1.setText("Try again!"); jTextField1.selectAll(); jTextField1.requestFocus(); >@Override public LoginPresenter getPresenter() < return loginPresenter; >@Override public void setPresenter(LoginPresenter loginPresenter) < this.loginPresenter = loginPresenter; >> interface LoginPresenter < LoginModel getModel(); void setModel(LoginModel loginModel); LoginView getView(); void setView(LoginView loginView); void setOnLogin(Runnable onLogin); void run(); void login(); >class MyLoginPresenter implements LoginPresenter < LoginModel loginModel; LoginView loginView; private Runnable onLogin; @Override public LoginModel getModel() < return loginModel; >@Override public void setModel(LoginModel loginModel) < this.loginModel = loginModel; >@Override public LoginView getView() < return loginView; >@Override public void setView(LoginView loginView) < this.loginView = loginView; >@Override public void setOnLogin(Runnable onLogin) < this.onLogin = onLogin; >@Override public void run() < loginModel.setUser("previousUser"); loginView.setPresenter(this); loginView.updateViewFromModel(); loginView.open(); >@Override public void login() < loginView.updateModelFromView(); if (loginModel.getUser().equalsIgnoreCase("root")) < loginView.close(); loginView.setPresenter(null);// for memory sanity. onLogin.run(); >else < loginView.userRejected(); >> > public class Application < /** * @param args the command line arguments */ public static void main(String args[]) < java.awt.EventQueue.invokeLater(new Runnable() < public void run() < LoginModel loginModel = new MyLoginModel(); LoginPresenter loginPresenter = new MyLoginPresenter(); loginPresenter.setModel(loginModel); LoginView loginView = new MyLoginView(); loginPresenter.setView(loginView); loginPresenter.setOnLogin(new Runnable() < @Override public void run() < JOptionPane.showMessageDialog(null, "Welcome user!"); >>); loginPresenter.run(); > >); > >