使用AWT组件实现验证码功能

import java.awt.Color;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.util.Random;

import javax.imageio.ImageIO;

public class Test {

    /**
     * @param args
     * @throws IOException 
     */
    public static void main(String[] args) throws IOException {
        //用于随机生成验证码的字符串集
        String[] strs = {"A","B","C","D","E","F","G","H","I","J","K","L","M","N","O","P","Q","R"
                        ,"S","T","U","V","W","X","Y","Z","a","b","c","d","e","f","g","h","i","j"
                        ,"k","l","m","n","o","p","q","r","s","t","u","v","w","x","y","z","0","1"
                        ,"2","3","4","5","6","7","8","9"};
        //随机生成干扰线的纵坐标y1和y2
        Random y1Random = new Random();
        Random y2Random = new Random();
        int y1 = y1Random.nextInt(31);
        int y2 = y2Random.nextInt(31);
        
        //随机生成用于组成验证码的字符串所在集的下标值
        Random code1Random = new Random();
        Random code2Random = new Random();
        Random code3Random = new Random();
        Random code4Random = new Random();
        int code1Index = code1Random.nextInt(62);
        int code2Index = code2Random.nextInt(62);
        int code3Index = code3Random.nextInt(62);
        int code4Index = code4Random.nextInt(62);
        
        //随机生成rgb颜色
        Random rRandom = new Random();
        Random gRandom = new Random();
        Random bRandom = new Random();
        int r = rRandom.nextInt(256);
        int g = gRandom.nextInt(256);
        int b = bRandom.nextInt(256);
        Color color = new Color(r, g, b);
        
        //拼接成完整字符串
        String codeString = strs[code1Index] + strs[code2Index] + strs[code3Index] + strs[code4Index];
        
        //定义一个宽70像素,高30像素的jpg图片
        BufferedImage bi = new BufferedImage(70, 30, BufferedImage.TYPE_INT_RGB);
        //定义graphis绘画对象
        Graphics2D graphics2d = bi.createGraphics();        
        graphics2d.setBackground(Color.WHITE);
        graphics2d.setColor(color);
        graphics2d.setFont(new Font(Font.SANS_SERIF, Font.BOLD, 20));
        graphics2d.clearRect(0, 0, 70, 30);
　　　　　　 //绘制干扰线
        graphics2d.drawLine(0, y1, 70, y2);
        
        //居中绘制字符串
        FontMetrics fontMetrics = graphics2d.getFontMetrics();
        int stringWidth = fontMetrics.stringWidth(codeString);
        int stringAscent = fontMetrics.getAscent();
        int xCode = 70 / 2 - stringWidth / 2;
        int yCode = 30 / 2 + stringAscent / 2;
        graphics2d.drawString(codeString, xCode, yCode);
        
        //输出图片
        File file = new File("C:\Users\zhengbing\Desktop\image.jpg");
        ImageIO.write(bi, "jpeg", file);
    }

}

最后可以返回校验字符串codeString,来达到验证的功能