package com.fgkj.servlets;

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

import sun.misc.BASE64Encoder;

public class IdentifyingServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		this.doPost(request, response);
	}

	
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {

		//服务器通知浏览器不要缓存
		response.setHeader("pragma","no-cache");
		response.setHeader("cache-control","no-cache");
		response.setHeader("expires","0");
		
		//在内存中创建一个长80，宽30的图片，默认黑色背景
		//参数一：长
		//参数二：宽
		//参数三：颜色
		int width = 80;
		int height = 30;
		BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
		
		//获取画笔
		Graphics g = image.getGraphics();
		//设置画笔颜色为灰色
		g.setColor(Color.GRAY);
		//填充图片
		g.fillRect(0,0, width,height);
		
		//产生4个随机验证码，12Ey
		String checkCode = getCheckCode();
		//将验证码放入HttpSession中
		request.getSession().setAttribute("CHECKCODE_SERVER",checkCode);
		
		//设置画笔颜色为黄色
		g.setColor(Color.YELLOW);
		//设置字体的小大
		g.setFont(new Font("黑体",Font.BOLD,24));
		//向图片上写入验证码
		g.drawString(checkCode,15,25);
		
		//将内存中的图片输出到浏览器
		//参数一：图片对象
		//参数二：图片的格式，如PNG,JPG,GIF
		//参数三：图片输出到哪里去
		//ImageIO.write(image,"PNG",response.getOutputStream());
		String png_base64=BufferedImageToBase64(image);
		OutputStream stream = response.getOutputStream();
		stream.write(png_base64.getBytes("UTF-8"));
		
	}
	/**
	 * 产生4位随机字符串 
	 */
	private String getCheckCode() {
		String base = "0123456789ABCDEFGHIJKLMNOPQRSTIVWXYZabcdefghijklmnopqrstuvwxyz";
		int size = base.length();
		Random r = new Random();
		StringBuffer sb = new StringBuffer();
		for(int i=1;i<=4;i++){
			//产生0到size-1的随机值
			int index = r.nextInt(size);
			//在base字符串中获取下标为index的字符
			char c = base.charAt(index);
			//将c放入到StringBuffer中去
			sb.append(c);
		}
		return sb.toString();

	}
    //BufferedImage转为base64字符串
	private String  BufferedImageToBase64(BufferedImage image){
		 ByteArrayOutputStream baos = new ByteArrayOutputStream();//io流
		 try {
			ImageIO.write(image, "png", baos);
		} catch (IOException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}//写入流中
         byte[] bytes = baos.toByteArray();//转换成字节
         BASE64Encoder encoder = new BASE64Encoder();
         String png_base64 = encoder.encodeBuffer(bytes).trim();//转换成base64串
         png_base64 = png_base64.replaceAll("\n", "").replaceAll("\r", "");//删除 \r\n
         
 //      ImageIO.write(bufferedImage, "png", new File("D:/qrcode1.png"));
         //System.out.println("值为："+"data:image/jpg;base64,"+png_base64);
         return   "data:image/jpg;base64,"+png_base64;
	}
}