我试过下面的一个例子，一切似乎都很好，除非你正在做一些不同的事情：

import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Insets;
import javax.swing.BorderFactory;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.SwingUtilities;
import javax.swing.border.Border;
import javax.swing.border.EmptyBorder;

public class TestApp {

    public TestApp() {
        createAndShowGui();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(TestApp::new);
    }

    private void createAndShowGui() {
        JFrame frame = new JFrame("TestApp");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

        JPanel panel = new JPanel();
        panel.setBorder(new EmptyBorder(20, 20, 20, 20));
        panel.setBackground(Color.WHITE);

        JButton button = new JButton("Primary");
        button.setOpaque(false);
        button.setBackground(null);
        button.setFocusPainted(false);
        button.setForeground(new Color(69, 143, 253));
        RoundedBorder blueLineBorder = new RoundedBorder(new Color(69, 143, 253), 10);
        Border emptyBorder = BorderFactory.createEmptyBorder(button.getBorder().getBorderInsets(button).top, button.getBorder().getBorderInsets(button).left, button.getBorder().getBorderInsets(button).bottom, button.getBorder().getBorderInsets(button).right);
        button.setBorder(BorderFactory.createCompoundBorder(blueLineBorder, emptyBorder));

        panel.add(button);

        frame.add(panel);
        frame.pack();
        frame.setVisible(true);
    }

    private static class RoundedBorder implements Border {

        private int radius = 10;
        private Color color;

        private RoundedBorder(Color color, int radius) {
            this.color = color;
            this.radius = radius;
        }

        @Override
        public Insets getBorderInsets(Component c) {
            return new Insets(this.radius + 1, this.radius + 1, this.radius + 1, this.radius + 1);
        }

        @Override
        public boolean isBorderOpaque() {
            return true;
        }

        @Override
        public void paintBorder(Component c, Graphics g, int x, int y, int width, int height) {
            g.setColor(color);
            g.drawRoundRect(x, y, width - 1, height - 1, radius, radius);
        }
    }
}