## 后端验证码文件 ```java package web; 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 { public void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { System.out.println("CheckcodeServlet's service"); /* * 一、绘图 */ /* * step1,创建一个内存映像对象(画布) * BufferedImage(宽度,高度,类型) */ BufferedImage image = new BufferedImage(80,30, BufferedImage.TYPE_INT_RGB); /* * step2,获得一个画笔 */ Graphics g = image.getGraphics(); /* * step3,给笔设置颜色 */ Random r = new Random(); g.setColor(new Color(255,255,255)); /* * step4,给画布设置背景颜色 * fillRect(x,y,width,height) */ g.fillRect(0, 0, 80, 30); /* * step5,绘图 */ g.setColor(new Color(r.nextInt(255), r.nextInt(255),r.nextInt(255))); //Font(字体,风格,大小) g.setFont(new Font(null,Font.ITALIC,22)); String number = getNumber(5); //将number绑订到session对象上 HttpSession session = request.getSession(); session.setAttribute("number", number); //drawString(String,x,y) x,y是左下角的坐标 g.drawString(number, 2, 23); //step6,加一些干扰线 for(int i=0;i<6;i++){ g.drawLine(r.nextInt(80), r.nextInt(30), r.nextInt(80), r.nextInt(30)); } /* * 二、将图片压缩并发送给浏览器 */ //设置content-type消息头，告诉 //浏览器返回的是图片 response.setContentType("image/jpeg"); //一定要获得字节输出流 OutputStream ops = response.getOutputStream(); //write方法会对原始图片(image)按照 //指定的压缩算法(jpeg)进行压缩，并且 //将压缩之后的数据输出到指定的流(ops)。 javax.imageio.ImageIO.write(image, "jpeg", ops); ops.close(); } /* * 生成一个验证码，该验证码由"A~Z","0~9"中 随机选取5个字符组成 */ private String getNumber(int size) { String rs = ""; String strs = "ABCDEFGHIJKLMNOPQ" + "RSTUVWXYZ0123456789"; Random r = new Random(); for(int i=0;i<size;i++){ rs += strs.charAt(r.nextInt(strs.length())); } return rs; } } ``` ## 前台的验证码的获取方式 ``` $(this).find( "img").attr("src" ,"../getcode.htm?num=" +num); ```