java动态验证码实例

以下是一个使用Java实现动态验证码的示例，它使用Java的Swing库来创建GUI并生成随机验证码：

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.util.Random;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;

public class DynamicCaptcha extends JPanel implements ActionListener {
    private static final long serialVersionUID = 1L;
    private String captchaString;
    private JTextField captchaTextField;
    private JButton submitButton;

    public DynamicCaptcha() {
        generateCaptcha();
        captchaTextField = new JTextField(20);
        submitButton = new JButton("Submit");
        submitButton.addActionListener(this);
        add(captchaTextField);
        add(submitButton);
    }

    public void generateCaptcha() {
        Random random = new Random();
        String alphabet = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
        StringBuilder sb = new StringBuilder();
        for (int i = 0; i < 6; i++) {
            sb.append(alphabet.charAt(random.nextInt(alphabet.length())));
        }
        captchaString = sb.toString();
    }

    public void paint(Graphics g) {
        super.paint(g);
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, getWidth(), getHeight());
        g.setColor(Color.BLACK);
        g.setFont(new Font("Arial", Font.BOLD, 24));
        g.drawString(captchaString, 100, 100);
    }

    public void actionPerformed(ActionEvent e) {
        String input = captchaTextField.getText();
        if (input.equals(captchaString)) {
            System.out.println("Captcha validation successful!");
        } else {
            System.out.println("Captcha validation failed!");
        }
    }

    public static void main(String[] args) {
        JFrame frame = new JFrame("Dynamic Captcha");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setSize(400, 200);
        frame.add(new DynamicCaptcha());
        frame.setVisible(true);
    }
}

这个示例代码创建了一个继承自JPanel的DynamicCaptcha类，它包含一个生成验证码的方法generateCaptcha()和一个重写paint()方法以在面板上绘制验证码。在main()方法中，它创建了一个JFrame并将DynamicCaptcha实例添加到其中以显示GUI。用户可以输入验证码并单击提交按钮来验证它是否正确。