黑马day04 画一个汉字的随机验证码的图片

下面的程序详细介绍了如何画一个随机验证码发送到客户端即浏览器进行显示：

1.画随机验证码的代码：

package cn.itheima.response;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
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;

public class ValiImage extends HttpServlet {
	public void doGet(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		//告知浏览器不缓存
		response.setDateHeader("Expires", -1);
		response.setHeader("Cache-Control", "no-cache");
		response.setHeader("Pragma", "no-cache");
		int height=30;
		int width=130;
		//1.得到内存中的图片
		BufferedImage image=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
		//2.得到画布
		Graphics2D g = (Graphics2D) image.getGraphics();
		//3.填充背景色
		g.setColor(Color.LIGHT_GRAY);
		g.fillRect(0, 0, width, height);
		//4.画一个矩形
		g.setColor(Color.black);
		g.drawRect(0, 0, width-1, height-1);
		//5.随机斜线
		for(int i=0;i<4;i++){
			g.setColor(Color.RED);
			g.drawLine(randNum(0,width), randNum(0,height), randNum(0,width), randNum(0,height));
		}
		//6.随机写一个汉字
		String base = "\u7684\u4e00\u4e86\u662f\u6211\u4e0d\u5728\u4eba\u4eec\u6709\u6765\u4ed6\u8fd9\u4e0a\u7740\u4e2a\u5730\u5230\u5927\u91cc\u8bf4\u5c31\u53bb\u5b50\u5f97\u4e5f\u548c\u90a3\u8981\u4e0b\u770b\u5929\u65f6\u8fc7\u51fa\u5c0f\u4e48\u8d77\u4f60\u90fd\u628a\u597d\u8fd8\u591a\u6ca1\u4e3a\u53c8\u53ef\u5bb6\u5b66\u53ea\u4ee5\u4e3b\u4f1a\u6837\u5e74\u60f3\u751f\u540c\u8001\u4e2d\u5341\u4ece\u81ea\u9762\u524d\u5934\u9053\u5b83\u540e\u7136\u8d70\u5f88\u50cf\u89c1\u4e24\u7528\u5979\u56fd\u52a8\u8fdb\u6210\u56de\u4ec0\u8fb9\u4f5c\u5bf9\u5f00\u800c\u5df1\u4e9b\u73b0\u5c71\u6c11\u5019\u7ecf\u53d1\u5de5\u5411\u4e8b\u547d\u7ed9\u957f\u6c34\u51e0\u4e49\u4e09\u58f0\u4e8e\u9ad8\u624b\u77e5\u7406\u773c\u5fd7\u70b9\u5fc3\u6218\u4e8c\u95ee\u4f46\u8eab\u65b9\u5b9e\u5403\u505a\u53eb\u5f53\u4f4f\u542c\u9769\u6253\u5462\u771f\u5168\u624d\u56db\u5df2\u6240\u654c\u4e4b\u6700\u5149\u4ea7\u60c5\u8def\u5206\u603b\u6761\u767d\u8bdd\u4e1c\u5e2d\u6b21\u4eb2\u5982\u88ab\u82b1\u53e3\u653e\u513f\u5e38\u6c14\u4e94\u7b2c\u4f7f\u5199\u519b\u5427\u6587\u8fd0\u518d\u679c\u600e\u5b9a\u8bb8\u5feb\u660e\u884c\u56e0\u522b\u98de\u5916\u6811\u7269\u6d3b\u90e8\u95e8\u65e0\u5f80\u8239\u671b\u65b0\u5e26\u961f\u5148\u529b\u5b8c\u5374\u7ad9\u4ee3\u5458\u673a\u66f4\u4e5d\u60a8\u6bcf\u98ce\u7ea7\u8ddf\u7b11\u554a\u5b69\u4e07\u5c11\u76f4\u610f\u591c\u6bd4\u9636\u8fde\u8f66\u91cd\u4fbf\u6597\u9a6c\u54ea\u5316\u592a\u6307\u53d8\u793e\u4f3c\u58eb\u8005\u5e72\u77f3\u6ee1\u65e5\u51b3\u767e\u539f\u62ff\u7fa4\u7a76\u5404\u516d\u672c\u601d\u89e3\u7acb\u6cb3\u6751\u516b\u96be\u65e9\u8bba\u5417\u6839\u5171\u8ba9\u76f8\u7814\u4eca\u5176\u4e66\u5750\u63a5\u5e94\u5173\u4fe1\u89c9\u6b65\u53cd\u5904\u8bb0\u5c06\u5343\u627e\u4e89\u9886\u6216\u5e08\u7ed3\u5757\u8dd1\u8c01\u8349\u8d8a\u5b57\u52a0\u811a\u7d27\u7231\u7b49\u4e60\u9635\u6015\u6708\u9752\u534a\u706b\u6cd5\u9898\u5efa\u8d76\u4f4d\u5531\u6d77\u4e03\u5973\u4efb\u4ef6\u611f\u51c6\u5f20\u56e2\u5c4b\u79bb\u8272\u8138\u7247\u79d1\u5012\u775b\u5229\u4e16\u521a\u4e14\u7531\u9001\u5207\u661f\u5bfc\u665a\u8868\u591f\u6574\u8ba4\u54cd\u96ea\u6d41\u672a\u573a\u8be5\u5e76\u5e95\u6df1\u523b\u5e73\u4f1f\u5fd9\u63d0\u786e\u8fd1\u4eae\u8f7b\u8bb2\u519c\u53e4\u9ed1\u544a\u754c\u62c9\u540d\u5440\u571f\u6e05\u9633\u7167\u529e\u53f2\u6539\u5386\u8f6c\u753b\u9020\u5634\u6b64\u6cbb\u5317\u5fc5\u670d\u96e8\u7a7f\u5185\u8bc6\u9a8c\u4f20\u4e1a\u83dc\u722c\u7761\u5174\u5f62\u91cf\u54b1\u89c2\u82e6\u4f53\u4f17\u901a\u51b2\u5408\u7834\u53cb\u5ea6\u672f\u996d\u516c\u65c1\u623f\u6781\u5357\u67aa\u8bfb\u6c99\u5c81\u7ebf\u91ce\u575a\u7a7a\u6536\u7b97\u81f3\u653f\u57ce\u52b3\u843d\u94b1\u7279\u56f4\u5f1f\u80dc\u6559\u70ed\u5c55\u5305\u6b4c\u7c7b\u6e10\u5f3a\u6570\u4e61\u547c\u6027\u97f3\u7b54\u54e5\u9645\u65e7\u795e\u5ea7\u7ae0\u5e2e\u5566\u53d7\u7cfb\u4ee4\u8df3\u975e\u4f55\u725b\u53d6\u5165\u5cb8\u6562\u6389\u5ffd\u79cd\u88c5\u9876\u6025\u6797\u505c\u606f\u53e5\u533a\u8863\u822c\u62a5\u53f6\u538b\u6162\u53d4\u80cc\u7ec6";
		for(int i=0;i<4;i++){
			g.setColor(Color.black);
			int r=randNum(-45, 45);
			g.rotate(1.0*r/180*Math.PI, 5+30*i, 21);//旋转?
			g.setFont(new Font("黑体", Font.BOLD, 15));
			g.drawString(base.charAt(randNum(0, base.length()-1))+"", 5+30*i, 21);
			g.rotate(1.0*-r/180*Math.PI, 5+30*i, 21);//旋转的是画布，因此旋转完，要归位
		}

		//将指定格式的文件输出到response缓冲区
		ImageIO.write(image, "jpg", response.getOutputStream());
	}
	//随机产生begin--end 之间的数字
	public int randNum(int begin,int end){
		Random rand=new Random();
		return rand.nextInt(end-begin)+begin;//5-10 10-5=5 5+5=10
	}
	public void doPost(HttpServletRequest request, HttpServletResponse response)
			throws ServletException, IOException {
		doGet(request, response);
	}

}

2.一个简单的登陆页面

<!DOCTYPE html>
<html>
  <head>
    <title>registOK.html</title>

    <meta http-equiv="content-type" content="text/html; charset=UTF-8">

    <!--<link rel="stylesheet" type="text/css" href="./styles.css">-->
	<script type="text/javascript">
		function changeImg(img){
			//当点击图片的时候就转到指定的连接进行刷新页面
			img.src="/day04/servlet/ValiImage?time="+new Date().getTime();
		}
	</script>
  </head>
<body>
	<form action="#" method="post">
		用户名：<input type="text" name="username"/><br/>
   		密码：<input type="password" name="password"/><br/>
   		验证码：<img style="cursor: pointer;" src="/day04/servlet/ValiImage" onclick="changeImg(this)">
   		<input type="submit" value="submit"/><br/>
	</form>

</body>
</html>

3.运行结果：