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package Servlet_FLC;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;

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;

public class NumServlet extends HttpServlet {
    public void doGet(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
      doPost(request,response);
    }

    
    public void doPost(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        //设置页面不缓存  
        response.setHeader("Pragma", "No-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);
        // 在内存中创建图象  
        int width = 60, height = 20;
        BufferedImage image = new BufferedImage(width, height,
                BufferedImage.TYPE_INT_RGB);
        // 获取图形上下文  
        Graphics g = image.getGraphics();
        //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));
        //画边框  
        //g.setColor(new Color());  
        //g.drawRect(0,0,width-1,height-1);  
        
        g.setColor(getRandColor(160, 200));
         //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  
        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(4位数字)  
        String sRand = "";
        for (int i = 0; i < 4; i++) {
            String rand = String.valueOf(random.nextInt(10));
            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);
        }
        // 将认证码存入SESSION  
        request.getSession().setAttribute("numrand", sRand);
        // 图象生效  
        g.dispose();  
        // 输出图象到页面  
        ImageIO.write(image, "JPEG", response.getOutputStream());
        
        
    }
    public Color getRandColor(int fc, int bc) {//给定范围获得随机颜色  
        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);
    }

    
}