生成的登录验证码Java类RandomCodeRender

import java.awt.Color;  import java.awt.Font;  import java.awt.Graphics;  import java.awt.image.BufferedImage;  import java.io.IOException;  import java.util.Random;  import javax.imageio.ImageIO;  import javax.servlet.ServletOutputStream;  import javax.servlet.http.Cookie;  import com.jfinal.render.Render;  import com.wangxiaowang.common.util.StringUtil;    public class RandomCodeRender extends Render {      private static final String[] strArr = {"3", "4", "5", "6", "7", "8", "9", "A", "B", "C", "D", "E", "F", "G", "H", "J", "K", "M", "N", "P", "Q", "R", "S", "T", "U", "V", "W", "X", "Y"};   static final int WIDTH = 85, HEIGHT = 20;      private String randomCodeKey;      public RandomCodeRender(String randomCodeKey) {    if (StringUtil.isBlank(randomCodeKey))     throw new IllegalArgumentException("randomCodeKey can not be blank");    this.randomCodeKey = randomCodeKey;   }      public void render() {    BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);    String vCode = drawGraphic(image);    vCode = RandomCodeService.encode(vCode);    Cookie cookie = new Cookie(randomCodeKey, vCode);    cookie.setMaxAge(-1);    cookie.setPath("/");    response.addCookie(cookie);    response.setHeader("Pragma","no-cache");          response.setHeader("Cache-Control","no-cache");          response.setDateHeader("Expires", 0);          response.setContentType("image/jpeg");                    ServletOutputStream sos = null;          try {     sos = response.getOutputStream();     ImageIO.write(image, "jpeg",sos);    } catch (Exception e) {     throw new RuntimeException(e);    }    finally {     try {sos.close();} catch (IOException e) {e.printStackTrace();}    }   }     private String drawGraphic(BufferedImage image){    // 获取图形上下文    Graphics g = image.createGraphics();    // 生成随机类    Random random = new Random();    // 设定背景色    g.setColor(getRandColor(200, 250));    g.fillRect(0, 0, WIDTH, HEIGHT);    // 设定字体    g.setFont(new Font("Times New Roman", Font.PLAIN, 18));      // 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到    g.setColor(getRandColor(160, 200));    for (int i = 0; i < 155; i++) {     int x = random.nextInt(WIDTH);     int y = random.nextInt(HEIGHT);     int xl = random.nextInt(12);     int yl = random.nextInt(12);     g.drawLine(x, y, x + xl, y + yl);    }      // 取随机产生的认证码(6位数字)    String sRand = "";    for (int i = 0; i < 6; i++) {     String rand = String.valueOf(strArr[random.nextInt(strArr.length)]);     sRand += rand;     // 将认证码显示到图象中     g.setColor(new Color(20 + random.nextInt(110), 20 + random.nextInt(110), 20 + random.nextInt(110)));     // 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     g.drawString(rand, 13 * i + 6, 16);    }      // 图象生效    g.dispose();        return sRand;   }      /*    * 给定范围获得随机颜色    */   private Color getRandColor(int fc, int bc) {    Random random = new Random();    if (fc > 255)     fc = 255;    if (bc > 255)     bc = 255;    int r = fc + random.nextInt(bc - fc);    int g = fc + random.nextInt(bc - fc);    int b = fc + random.nextInt(bc - fc);    return new Color(r, g, b);   }  }