生成验证码

/**
 * 
 */
package org.jeecgframework.web.system.servlet;

import org.jeecgframework.core.util.ResourceUtil;

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

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;


/**
 * 随机生成验证图片
 * 
 * 
 */
public class RandCodeImageServlet extends HttpServlet {
    private static final long serialVersionUID = -1257947018545327308L;
    private static final String SESSION_KEY_OF_RAND_CODE = "randCode"; // todo 要统一常量
    /**
     * 
     */
    private static final int count = 200;

    /**
     * 定义图形大小
     */
    private static final int width = 105;
    /**
     * 定义图形大小
     */
    private static final int height = 35;
    // private Font mFont = new Font("Arial Black", Font.PLAIN, 15); //设置字体
    /**
     * 干扰线的长度=1.414*lineWidth
     */
    private static final int lineWidth = 2;

    @Override
    public void doGet(final HttpServletRequest request,
            final HttpServletResponse response) throws ServletException,
            IOException {
        // 设置页面不缓存
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        // response.setContentType("image/png");

        // 在内存中创建图象
        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); // ---1
        graphics.fillRect(0, 0, width, height);
        // 设定边框颜色
//        graphics.setColor(getRandColor(100, 200)); // ---2
        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 - lineWidth - 1) + 1; // 保证画在边框之内
            final int y = random.nextInt(height - lineWidth - 1) + 1;
            final int xl = random.nextInt(lineWidth);
            final int yl = random.nextInt(lineWidth);
            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();
        for (int i = 0; i < resultCode.length(); i++) {
            // 将认证码显示到图象中,调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
            // graphics.setColor(new Color(20 + random.nextInt(130), 20 + random
            // .nextInt(130), 20 + random.nextInt(130)));

            // 设置字体颜色
            graphics.setColor(Color.BLACK);
            // 设置字体样式
//            graphics.setFont(new Font("Arial Black", Font.ITALIC, 18));
            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)), (23 * i) + 8, 26);
        }

        // 将认证码存入SESSION
        request.getSession().setAttribute(SESSION_KEY_OF_RAND_CODE, resultCode);
        // 图象生效
        graphics.dispose();

        // 输出图象到页面
        ImageIO.write(image, "JPEG", response.getOutputStream());
    }

    @Override
    public void doPost(final HttpServletRequest request,
            final HttpServletResponse response) throws ServletException,
            IOException {
        doGet(request, response);
    }

    /**
     * @return 随机码
     */
    private String exctractRandCode() {
        final String randCodeType = "5";
        int randCodeLength = Integer.parseInt("4");
        if (randCodeType == null) {
            return RandCodeImageEnum.NUMBER_CHAR.generateStr(randCodeLength);
        } else {
            switch (randCodeType.charAt(0)) {
            case '1':
                return RandCodeImageEnum.NUMBER_CHAR.generateStr(randCodeLength);
            case '2':
                return RandCodeImageEnum.LOWER_CHAR.generateStr(randCodeLength);
            case '3':
                return RandCodeImageEnum.UPPER_CHAR.generateStr(randCodeLength);
            case '4':
                return RandCodeImageEnum.LETTER_CHAR.generateStr(randCodeLength);
            case '5':
                return RandCodeImageEnum.ALL_CHAR.generateStr(randCodeLength);

            default:
                return RandCodeImageEnum.NUMBER_CHAR.generateStr(randCodeLength);
            }
        }
    }

    /**
     * 描述：
     * 
     * @param fc
     *            描述：
     * @param bc
     *            描述：
     * 
     * @return 描述：
     */
    private Color getRandColor(int fc, int bc) { // 取得给定范围随机颜色
        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 StringBuffer sb = new StringBuffer();
        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;
    }

}