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