drawrandnumber.java

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package com.yhcms.manage.admin.biz;

import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Random;
import javax.servlet.http.HttpServletRequest;

public class DrawRandNumber
{

    private static BufferedImage image = new BufferedImage(50, 20, 1);
    private static DrawRandNumber instance = new DrawRandNumber();
    public static final Random RANDOM = new Random();

    private DrawRandNumber()
    {
    }

    private void init()
    {
    }

    public static DrawRandNumber getInstance()
    {
        return instance;
    }

    public synchronized String writeRandNumber(int bits, int to, HttpServletRequest request)
        throws IOException
    {
        String rand = getRandNumber(bits, to);
        setSession(request, rand);
        return rand;
    }

    public synchronized Image drawRandNumber(int bits, int to, HttpServletRequest request)
    {
        String rand = getRandNumber(bits, to);
        Graphics g = image.getGraphics();
        refreshBgColor(g);
        g.setColor(getRandColor(20, 130));
        g.drawString(rand, 6, 16);
        g.dispose();
        setSession(request, rand);
        return image;
    }

    private String getRandNumber(int bits, int to)
    {
    	StringBuffer randBuffer = new StringBuffer();
        for(int i = 1; i <= bits; i++)
            randBuffer.append(RANDOM.nextInt(to));

        return randBuffer.toString();
    }

    private void setSession(HttpServletRequest request, String rand)
    {
    	request.getSession(true).setAttribute("rand",rand);
    }

    private void refreshBgColor(Graphics g)
    {
        g.fillRect(0, 0, 50, 20);
        g.setFont(new Font("Times New Roman", 0, 18));
        g.setColor(getRandColor(160, 200));
        for(int i = 0; i < 100; i++)
        {
            int x = RANDOM.nextInt(50);
            int y = RANDOM.nextInt(20);
            int xl = RANDOM.nextInt(12);
            int yl = RANDOM.nextInt(12);
            g.drawLine(x, y, x + xl, y + yl);
        }

    }

    private Color getRandColor(int fc, int bc)
    {
        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);
    }

}