生成随机码验证

package com.weis.utils;

import java.awt.Color;
import java.awt.Font;
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;

import org.apache.commons.lang.StringUtils;


/**
 * 随机生成验证码图片
 */
public class RandCodeImageUtil {
    
    private static final int COUNT = 200;
    /**
     * 定义图形长度
     */
    private static final int WIDTH = 100;
    /**
     * 定义图形高度
     */
    private static final int HEIGHT = 25;
    /**
     * 干扰线的长度=1.414*LINE_WIDTH
     */
    private static final int LINE_WIDTH = 2;

    /**
     * 验证码缓存
     */
    public static final String LOGIN_CAPTCHA = "_LOGIN_CAPTCHA";
    public static final String LOGIN_CAPTCHA_NAMESPACE = "RandCode";
    
    public static void main(String[] args) throws IOException {
        createRandImage();
    }

    private static void createRandImage() throws IOException {
        // 设置页面不缓存
        //response.setHeader("Pragma", "No-cache");
        //response.setHeader("Cache-Control", "no-cache");
        //response.setDateHeader("Expires", 0);
        // 在内存中创建图像
        final BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);
        // 获取图形上下文
        final Graphics2D graphics = (Graphics2D) image.getGraphics();
        // 设定背景颜色
        graphics.setColor(Color.WHITE);
        graphics.fillRect(0, 0, WIDTH, HEIGHT);
        graphics.drawRect(0, 0, WIDTH - 1, HEIGHT - 1);
        final Random random = new Random();
        // 随机产生干扰线，使图象中的认证码不易被其它程序探测到
        for (int i = 0; i < COUNT; i++) {
            graphics.setColor(getRandColor(150, 200)); // ---3
            final int x = random.nextInt(WIDTH - LINE_WIDTH - 1) + 1; // 保证画在边框之内
            final int y = random.nextInt(HEIGHT - LINE_WIDTH - 1) + 1;
            final int xl = random.nextInt(LINE_WIDTH);
            final int yl = random.nextInt(LINE_WIDTH);
            graphics.drawLine(x, y, x + xl, y + yl);
        }
        // 取随机产生的认证码(4位数字)
        final String resultCode = exctractRandCode(null,4);
        for (int i = 0; i < resultCode.length(); i++) {
            // 设置字体颜色 Color.BLACK
            graphics.setColor(new Color(0, 189, 206));
            // 设置字体样式
            graphics.setFont(new Font("Times New Roman", Font.BOLD, 24));
            // 设置字符，字符间距，上边距
            graphics.drawString(String.valueOf(resultCode.charAt(i)), (20 * i) + 6, 20);
        }

        // 图象生效
        graphics.dispose();
        // 输出图象到页面
        ImageIO.write(image, "JPEG", new File("d://a.JPEG"));
        //ImageIO.write(image, "JPEG", response.getOutputStream());
    }


    /**
     * 随机码
     * @param randCodeType 验证码类型：1数字，2小写字母，3大学字母，4字符，5混合字符串
     * @param randCodeLength 验证码长度
     * @return
     */
    private static String exctractRandCode(String randCodeType, int randCodeLength) {
        if (StringUtils.isBlank(randCodeType)) {
            return RandCodeImageEnum.NUMBER_CHAR.generateStr(randCodeLength);
        }
        return switchRandCode(randCodeType.charAt(0), randCodeLength);
    }

    private static String switchRandCode(char randCodeType, int randCodeLength) {
        switch (randCodeType) {
            case '2':
                // 小写
                return RandCodeImageEnum.LOWER_CHAR.generateStr(randCodeLength);
            case '3':
                // 大写
                return RandCodeImageEnum.UPPER_CHAR.generateStr(randCodeLength);
            case '4':
                // 字符
                return RandCodeImageEnum.LETTER_CHAR.generateStr(randCodeLength);
            case '5':
                // 混合字符串
                return RandCodeImageEnum.ALL_CHAR.generateStr(randCodeLength);
            default:
                return RandCodeImageEnum.NUMBER_CHAR.generateStr(randCodeLength);
        }
    }

    /**
     * 取得给定范围随机颜色
     * 
     * @param fc
     * @param bc
     * @return
     */
    private static Color getRandColor(int fc, int bc) {
        final Random random = new Random();
        if (fc > 255) {
            fc = 255;
        }
        if (bc > 255) {
            bc = 255;
        }
        final int r = fc + random.nextInt(bc - fc);
        final int g = fc + random.nextInt(bc - fc);
        final int b = fc + random.nextInt(bc - fc);
        return new Color(r, g, b);
    }

}


/**
 * 验证码辅助类
 *
 */
enum RandCodeImageEnum {
    /**
     * 混合字符串
     */
    ALL_CHAR("0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"),
    /**
     * 字符
     */
    LETTER_CHAR("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ"),
    /**
     * 小写字母
     */
    LOWER_CHAR("abcdefghijklmnopqrstuvwxyz"),
    /**
     * 数字
     */
    NUMBER_CHAR("0123456789"),
    /**
     * 大写字符
     */
    UPPER_CHAR("ABCDEFGHIJKLMNOPQRSTUVWXYZ");
    /**
     * 待生成的字符串
     */
    private String charStr;

    /**
     * @param charStr
     */
    private RandCodeImageEnum(final String charStr) {
        this.charStr = charStr;
    }

    /**
     * 生产随机验证码
     * 
     * @param codeLength 验证码的长度
     * @return 验证码
     */
    public String generateStr(final int codeLength) {
        final StringBuilder sb = new StringBuilder();
        final Random random = new Random();
        final String sourseStr = getCharStr();
        for (int i = 0; i < codeLength; i++) {
            sb.append(sourseStr.charAt(random.nextInt(sourseStr.length())));
        }
        return sb.toString();
    }

    /**
     * @return the {@link #charStr}
     */
    public String getCharStr() {
        return charStr;
    }
}