java_验证码模块(servlet).md

java_验证码模块(servlet)


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.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
@SuppressWarnings("serial" )
public class CheckCodeImage extends HttpServlet {
       private Font mFont = new Font( "Arial Black", Font.PLAIN, 16);//字体

       /**
       * 获得随机颜色
       * @param fc 颜色值下限
       * @param bc 颜色值上限
       * @return
       */
       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);
      }

       public void doGet(HttpServletRequest request, HttpServletResponse response)
                   throws ServletException, IOException {
            
             //取消缓存
            response.setHeader( "Pragma", "No-cache" );
            response.setHeader( "Cache-Control", "no-cache" );
            response.setDateHeader( "Expires", 0);
            response.setContentType( "image/jpeg");// 设置响应内容为图片
             int width = 58, height = 28;// 图片高度、宽度
            BufferedImage image = new BufferedImage(width, height,
                        BufferedImage. TYPE_INT_RGB);// 构造图片生成器
            Graphics g = image.getGraphics(); //构造画板
            Random random = new Random();// 随机数生成器
            g.setColor(getRandColor(200, 250)); //获得随机颜色
            g.fillRect(1, 1, width - 1, height - 1); //填充矩形
            g.setColor( new Color(102, 102, 102));
            g.drawRect(0, 0, width + 1, height - 1); //绘制矩形的边框
            g.setFont( mFont);// 设置字体
            g.setColor(getRandColor(160, 200));
             for (int i = 0; i < 155; i++) {//画 155条随机直线
                   int x = random.nextInt(width - 1);
                   int y = random.nextInt(height - 1);
                   int xl = random.nextInt(6) + 1;
                   int yl = random.nextInt(12) + 1;
                  g.drawLine(x, y, x + xl, y + yl);
            }
             for (int i = 0; i < 70; i++) {//画 70条随机直线
                   int x = random.nextInt(width - 1);
                   int y = random.nextInt(height - 1);
                   int xl = random.nextInt(12) + 1;
                   int yl = random.nextInt(6) + 1;
                  g.drawLine(x, y, x - xl, y - yl);
            }
            String sRand = "";
             for (int i = 0; i < 4; i++) { //画 4个随机字符串
                  String tmp = getRandomChar();
                  sRand += tmp;
                  g.setColor( new Color(20 + random.nextInt(110), 20 + random
                              .nextInt(110), 20 + random.nextInt(110)));
                  g.drawString(tmp, 12 * i + 1, 18); //画随机字符串
            }
            HttpSession session = request.getSession( true);
            session.setAttribute( "checkCodeImage", sRand); // 绑定这个随机字符串到 session
            g.dispose(); //释放资源
            ImageIO. write(image, "JPEG", response.getOutputStream());
      }

       private String getRandomChar() { // 获得随机字符串
             int rand = (int) Math.round(Math.random() * 2);
             long itmp = 0;
             char ctmp = '\u0000' ;
             switch (rand) {
             case 1:
                  itmp = Math. round(Math.random () * 25 + 65);
                  ctmp = ( char) itmp;
                   return String.valueOf(ctmp);
             case 2:
                  itmp = Math. round(Math.random () * 25 + 97);
                  ctmp = ( char) itmp;
                   return String.valueOf(ctmp);
             default:
                  itmp = Math. round(Math.random () * 9);
                   return String.valueOf(itmp);
            }
      }

       public void doPost(HttpServletRequest request, HttpServletResponse response)
                   throws ServletException, IOException {
             this.doGet(request, response);
      }

}