GreetUI.java

package org.example.gui;

import java.awt.Container;
import java.awt.Dimension;
import java.awt.event.*;
import javax.swing.*;
import org.example.api.Greeting;
import aQute.bnd.annotation.component.*;

@Component
public class GreetUI extends JFrame {

    private Greeting greeting;

    public GreetUI() {
        Container content = getContentPane();
        content.setLayout(new BoxLayout(content, BoxLayout.LINE_AXIS));
        
        content.add(new JLabel("Name:"));
        final JTextField text = new JTextField();
        text.setPreferredSize(new Dimension(100, 0));
        content.add(text);
        final JButton button = new JButton("Greet");
        content.add(button);

        button.addActionListener(new ActionListener() {
            public void actionPerformed(ActionEvent e) {
                String response = (greeting != null)
                    ? greeting.sayHello(text.getText())
                    : "Greeting service unavailable";
                JOptionPane.showMessageDialog(button, response);
            }
        });
    }

    @Reference
    public void setGreeting(Greeting greeting) {
        this.greeting = greeting;
    }

    @Activate
    public void start() {
        pack();
        setVisible(true);
    }

    @Deactivate
    public void stop() {
        setVisible(false);
    }

    public static void main(String[] args) {
        new GreetUI().start();
    }
}