Java算术验证码

CaptcahCode类

package com.jiegeng.code;


import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletResponse;
import java.awt.*;
import java.awt.font.FontRenderContext;
import java.awt.geom.Rectangle2D;
import java.awt.image.BufferedImage;
import java.util.Random;

/**
 * 验证码工具类
 */
public class CaptcahCode {

    /**
     * 算术表达式验证码
     *
     * 1.干扰线的产生
     * 2.范围随机颜色，随机数
     *
     * @param response
     * @return
     */
    public static String drawImageVerificate(HttpServletResponse response) {
        //定义验证码的宽度和高度
        int width = 120;
        int height = 25;
        //在内存中创建图片
        BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
        //创建图片上下文
        Graphics2D g = image.createGraphics();
        //产生随机对象，此随机对象主要用于算术表达式的数字
        Random random= new Random();
        //设置背景
        g.setColor(getRandomColor(240,250));
        //设置字体
        g.setFont(new Font("微软雅黑",Font.PLAIN,22 ));
        //开始绘制
        g.fillRect(0,0,width,height);

        //干扰线的绘制，绘制干扰线到图片中
        g.setColor(getRandomColor(180,230));
        for (int i = 0; i < 100; i++) {
            int x = random.nextInt(width);
            int y = random.nextInt(height);
            int x1 = random.nextInt(60);
            int y1 = random.nextInt(60);
            g.drawLine(x,y,x1,y1);
        }

        //开始进行对算术验证码表达式的拼接
        int num1 = (int)(Math.random()*10+1);
        int num2 = (int)(Math.random()*10+1);
        int fuhao = random.nextInt(3);//产生一个0-2之间的随机整数
        //记录符号
        String fuhaostr = null;
        int result = 0;
        switch (fuhao){
            case 0: fuhaostr = "+";result = num1 + num2;break;
            case 1: fuhaostr = "-";result = num1 - num2;break;
            case 2: fuhaostr = "*";result = num1 * num2;break;
        }
        //拼接算术表达式，用户图片显示
        String calc = num1 + " " + fuhaostr + " " + num2 + " = ?";
        //设置随机颜色
        g.setColor(new Color(20+random.nextInt(110),20+random.nextInt(110),20+random.nextInt(110)));
        //绘制表达式
        g.drawString(calc,5,25);
        //结束绘制
        try {
            //输出图片到页面
            ImageIO.write(image, "jpg", response.getOutputStream());
            return String.valueOf(result);
        }catch (Exception e){
            e.printStackTrace();
            return null;
        }
    }

    /**
     * 范围随机颜色
     *
     * @param fc
     * @param bc
     * @return
     */
    public static Color getRandomColor(int fc, int bc) {
        //利用随机数
        Random random = new Random();
        //随机颜色，了解颜色-Color(red,green,blue).rgb三元色0-255
        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);
    }
}

code.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<%
    //1.清空浏览器缓存。目的是为了清除浏览器的缓存，因为浏览器
    //会对网站的资源文件和图像进行记忆存储，如果被浏览器加载过的图片会被记忆起来
    //文件就不会和服务器做交互，如果我们验证不清空的话可能会造成一个问题就是，验证刷新以后没有效果

    response.setHeader("pragma","no-cache");
    response.setHeader("cache-control","no-cache");
    response.setHeader("expires","0");

    //2.调用编写的生成验证码工具
    String code = CaptcahCode.drawImageVerificate(response);
    session.setAttribute("code", code);

    //3.如何解决getOutputStream()异常问题
    out.clear();
    out=pageContext.pushBody();
%>


    

index.jsp

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

  
    
    
    
    
  
  
    
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