跨域验证码生成问题.

因为跨域 导致 session中的id不一致.

String captchaId = request.getSession().getId();

解决方案:
1.跨域后传送cookie,保持两个请求sessionid一致.
2.将生成的验证码存放到内存的缓存中. 然后验证就从缓存中对比. (近似验证)

package com.hupun.console.dubbo.http.proxy.rest.controller;

import com.bstek.common.log.Logger;
import com.bstek.common.log.LoggerFactory;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;

import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;


public class RandomValidateCode {

    private static Logger logger = LoggerFactory.getInstance().getLogger(RandomValidateCode.class);
    private Random random     = new Random();
    private String randString = "123456789ABCDEFGHIJKLMNPQRSTUVWXYZ"; // 随机产生的字符串

    private int    width      = 80;                                  // 图片宽
    private int    height     = 26;                                  // 图片高
    private int    lineSize   = 40;                                  // 干扰线数量
    private int    stringNum  = 4;                                   // 随机产生字符数量

    /*
     * 获得字体
     */
    private Font getFont() {
        return new Font("Fixedsys", Font.CENTER_BASELINE, 18);
    }

    /*
     * 获得颜色
     */
    private Color getRandColor(int fc, int bc) {
        if (fc > 255) fc = 255;
        if (bc > 255) bc = 255;
        int r = fc + random.nextInt(bc - fc - 16);
        int g = fc + random.nextInt(bc - fc - 14);
        int b = fc + random.nextInt(bc - fc - 18);
        return new Color(r, g, b);
    }

    /**
     * 生成随机图片
     */
    public String getRandcode(HttpServletRequest request, HttpServletResponse response) {
//        HttpSession session = request.getSession();
        // BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类
        String randomString = "";
        try {
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_BGR);
        Graphics g = image.getGraphics();// 产生Image对象的Graphics对象,改对象可以在图像上进行各种绘制操作
        g.fillRect(0, 0, width, height);
        g.setFont(new Font("Times New Roman", Font.ROMAN_BASELINE, 18));
        g.setColor(getRandColor(110, 133));
        // 绘制干扰线
        for (int i = 0; i <= lineSize; i++) {
            drowLine(g);
        }
        // 绘制随机字符

        for (int i = 1; i <= stringNum; i++) {
            randomString = drowString(g, randomString, i);
        }
//        session.removeAttribute(Constant.RANDOMCODEKEY);
//        session.setAttribute(Constant.RANDOMCODEKEY, randomString);
            g.dispose();
            ImageIO.setUseCache(false);
            ImageIO.write(image, "JPEG", response.getOutputStream());// 将内存中的图片通过流动形式输出到客户端
        } catch (Exception e) {
            logger.error(e, "生成随机图片失败!");
        }
        return randomString;
    }

    /*
     * 绘制字符串
     */
    private String drowString(Graphics g, String randomString, int i) {
        g.setFont(getFont());
        g.setColor(new Color(random.nextInt(101), random.nextInt(111), random.nextInt(121)));
        String rand = String.valueOf(getRandomString(random.nextInt(randString.length())));
        randomString += rand;
        g.translate(random.nextInt(3), random.nextInt(3));
        g.drawString(rand, 13 * i, 16);
        return randomString;
    }

    /*
     * 绘制干扰线
     */
    private void drowLine(Graphics g) {
        int x = random.nextInt(width);
        int y = random.nextInt(height);
        int xl = random.nextInt(13);
        int yl = random.nextInt(15);
        g.drawLine(x, y, x + xl, y + yl);
    }

    /*
     * 获取随机的字符
     */
    public String getRandomString(int num) {
        return String.valueOf(randString.charAt(num));
    }
}