Servlet生成随机验证码

package com.yc.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.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

@WebServlet("/code")
public class CreateCodeServlet extends HttpServlet{
private static final long serialVersionUID = -8482385671566727162L;

   @Override
   protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
       response.setHeader("Pragma", "no-cache");
       response.setHeader("Cache-Control", "no-cache");
       response.setDateHeader("Expires", 0);
       String code = getRandomCode();

       // 将随机生成的验证码存到session中，以便用户登录的时候获取校验
       HttpSession session = request.getSession();
       session.setAttribute("validateCode", code);

// 创建验证码图形对象，大小为110*28
BufferedImage image = getCodeImage(code, 110, 28);

ImageIO.write(image, "JPEG", response.getOutputStream());
}

   /**
   * 获取验证码图形
   * @param code
   * @param width
   * @param height
   * @return
   */
   private BufferedImage getCodeImage(String code, int width, int height) {
       // 创建图形对象
       BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

       // 获取图形的绘制绘制对象
       Graphics g = image.getGraphics();

       // 设置图形的背景颜色
       g.setColor(getRandomColor(225, 30));

// 设置绘制的边界
g.fillRect(0, 0, width, height);

// 设置字体 Courier New
g.setFont(new Font("楷体", Font.ITALIC, 20));

// 生产干扰线

       // 设置干扰线的颜色
       g.setColor(getRandomColor(160, 40));

       // 随机绘制干扰线
       int x1, y1, x2, y2;
       Random rd = new Random();
       for (int i = 0; i < 100; i++) {
           x1 = rd.nextInt(width);
           y1 = rd.nextInt(height);
           x2 = rd.nextInt(width);
           y2 = rd.nextInt(height);
           g.drawLine(x1, y1, x2, y2);
       }

       // 绘制验证码
       char[] codes = code.toCharArray();
       for (int i = 0, len = codes.length; i < len; i++) {
           // 设置验证码绘制的颜色
           g.setColor(getRandomColor(50, 80));

g.drawString(String.valueOf(codes[i]), 10 + 24*i, 20);
}

g.dispose();

return image;
}

   /**
   * 生成验证码的方法
   * @return
   */
   private String getRandomCode() {
       // 如何生存4位的随机验证码？ - 包含大写字母、小写字母和数字
       Random rd = new Random();
       StringBuffer sbf = new StringBuffer();
       int flag;
       for (int i = 0; i < 4; i++) {
           flag = rd.nextInt(4);
           switch(flag) {
           case 0: sbf.append(rd.nextInt(10)); break; // 生成数字
           case 1: sbf.append((char)(rd.nextInt(26) + 65)); break; // 生成大写字母
           case 2: sbf.append((char)(rd.nextInt(26) + 97)); break;   // 生成小写字母
           case 3: sbf.append((char)(rd.nextInt(20000) + 19968)); break;   // 生成小写字母
           }
       }
       return sbf.toString();
   }

   /**
   * 获取随机颜色的方法
   * @return
   */
   private Color getRandomColor(int start, int bound) {
       Random rd = new Random();
       int r = start + rd.nextInt(bound);
       int g = start + rd.nextInt(bound);
       int b = start + rd.nextInt(bound);
       return new Color(r, g, b);
   }
}

Servlet生成随机验证码

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