package com.jy.servlet;
/*
 * 时间:2018-08-08
 * 作者：黄奇
 * */
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;

public class CheckCodeServlet extends HttpServlet{
	private static final long serialVersionUID = 8597644014366031304L;

	public void service(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		/*
		 * 绘图
		 */
		//1.创建一个内存映像对象(画布)。
		BufferedImage image = 
			new BufferedImage(80,30,
					BufferedImage.TYPE_INT_RGB);
		//2.获得画笔
		Graphics g = image.getGraphics();
		//3.给画笔上色
		Random r = new Random();
		g.setColor(new Color(r.nextInt(255),
				r.nextInt(255),r.nextInt(255)));
		//4.开始绘图
		//4.1给画布设置背景颜色 
		g.fillRect(0, 0, 80, 30);
		//4.2给画笔设置一个颜色
		g.setColor(new Color(0,0,0));
		g.setFont(new Font(null,Font.ITALIC,20));
		//4.3在画布上绘图
		//A~Z,0~9随机选取５位
		String number = getNumber(5);
		//将验证码(number)绑订到session对象上
		HttpSession session = request.getSession();
		session.setAttribute("number", number);
		g.drawString(number, 5, 20);
		//4.4加上一些干扰线
		for(int i=0;i<8;i++){
			g.drawLine(r.nextInt(80),
					r.nextInt(30), 
					r.nextInt(80), 
					r.nextInt(30));
		}
		/*
		 * 将图片压缩并输出  
		 */
		//1.设置content-type消息头，告诉浏览器
		//返回的是一个jpeg格式的图片
		response.setContentType("image/jpeg");
		//2.获得一个字节输出流(因为是图片)
		OutputStream ops = 
			response.getOutputStream();
		//3.将图片压缩并输出
		javax.imageio.ImageIO
		.write(image, "jpeg", ops);
		ops.close();
		
	}
	
	/*
	 * 返回指定长度的一个字符串
	 * (由A~Z,0~9中选取)
	 */
	private String getNumber(int size) {
		String number = "";
		String chars = "ABCDEFGHI" +
				"JKLMNOPQRSTUVWXYZ01234" +
				"56789";
		Random r = new Random();
		for(int i=0;i<size;i++){
			number += chars.charAt(
					r.nextInt(chars.length()));
		}
		return number;
	}

}