package com.fgkj.servlets;
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import java.awt.Color;
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import java.awt.Font;
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import java.awt.Graphics;
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import java.awt.image.BufferedImage;
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import java.io.ByteArrayOutputStream;
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import java.io.IOException;
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import java.io.OutputStream;
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import java.io.PrintWriter;
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import java.util.Random;
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import javax.imageio.ImageIO;
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import javax.servlet.ServletException;
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import javax.servlet.http.HttpServlet;
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import javax.servlet.http.HttpServletRequest;
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import javax.servlet.http.HttpServletResponse;
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import sun.misc.BASE64Encoder;
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public class IdentifyingServlet extends HttpServlet {
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public void doGet(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException {
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this.doPost(request, response);
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}
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public void doPost(HttpServletRequest request, HttpServletResponse response)
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throws ServletException, IOException {
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//服务器通知浏览器不要缓存
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response.setHeader("pragma","no-cache");
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response.setHeader("cache-control","no-cache");
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response.setHeader("expires","0");
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//在内存中创建一个长80，宽30的图片，默认黑色背景
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//参数一：长
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//参数二：宽
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//参数三：颜色
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int width = 80;
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int height = 30;
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BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
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//获取画笔
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Graphics g = image.getGraphics();
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//设置画笔颜色为灰色
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g.setColor(Color.GRAY);
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//填充图片
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g.fillRect(0,0, width,height);
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//产生4个随机验证码，12Ey
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String checkCode = getCheckCode();
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//将验证码放入HttpSession中
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request.getSession().setAttribute("CHECKCODE_SERVER",checkCode);
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//设置画笔颜色为黄色
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g.setColor(Color.YELLOW);
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//设置字体的小大
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g.setFont(new Font("黑体",Font.BOLD,24));
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//向图片上写入验证码
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g.drawString(checkCode,15,25);
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//将内存中的图片输出到浏览器
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//参数一：图片对象
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//参数二：图片的格式，如PNG,JPG,GIF
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//参数三：图片输出到哪里去
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//ImageIO.write(image,"PNG",response.getOutputStream());
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String png_base64=BufferedImageToBase64(image);
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OutputStream stream = response.getOutputStream();
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stream.write(png_base64.getBytes("UTF-8"));
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}
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/**
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* 产生4位随机字符串
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*/
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private String getCheckCode() {
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String base = "0123456789ABCDEFGHIJKLMNOPQRSTIVWXYZabcdefghijklmnopqrstuvwxyz";
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int size = base.length();
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Random r = new Random();
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StringBuffer sb = new StringBuffer();
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for(int i=1;i<=4;i++){
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//产生0到size-1的随机值
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int index = r.nextInt(size);
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//在base字符串中获取下标为index的字符
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char c = base.charAt(index);
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//将c放入到StringBuffer中去
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sb.append(c);
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}
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return sb.toString();
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}
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//BufferedImage转为base64字符串
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private String BufferedImageToBase64(BufferedImage image){
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ByteArrayOutputStream baos = new ByteArrayOutputStream();//io流
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try {
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ImageIO.write(image, "png", baos);
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} catch (IOException e) {
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// TODO Auto-generated catch block
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e.printStackTrace();
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}//写入流中
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byte[] bytes = baos.toByteArray();//转换成字节
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BASE64Encoder encoder = new BASE64Encoder();
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String png_base64 = encoder.encodeBuffer(bytes).trim();//转换成base64串
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png_base64 = png_base64.replaceAll("\n", "").replaceAll("\r", "");//删除 \r\n
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// ImageIO.write(bufferedImage, "png", new File("D:/qrcode1.png"));
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//System.out.println("值为："+"data:image/jpg;base64,"+png_base64);
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return "data:image/jpg;base64,"+png_base64;
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}
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}
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