Java生成验证码

代码如下：

                response.setContentType("image/jpeg");
		ServletOutputStream out = response.getOutputStream();
		// 定义验证码边框的长和高
		int width = 60;
		int height = 20;
		// 定义图片缓冲区，使用RGB模式输出图片
		BufferedImage img = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);
		// 定义画笔工具对象
		Graphics graph = img.getGraphics();
		// 设置验证码框的背景颜色
		graph.setColor(new Color(200, 200, 200));
		// 使用上面设置的颜色填充整个矩形框
		graph.fillRect(0, 0, width, height);
		// 定义要显示的验证码
		StringBuffer codeStr = new StringBuffer("");
		// 定义验证码数组
		String code[] = { "A", "a", "B", "b", "C", "c", "D", "d", "E", "e",
				"F", "f", "G", "g", "H", "h", "I", "i", "J", "j", "K", "k",
				"L", "l", "M", "m", "N", "n", "O", "o", "P", "p", "Q", "q",
				"R", "r", "S", "s", "T", "t", "U", "u", "V", "v", "W", "w",
				"X", "x", "Y", "y", "Z", "z", "0", "1", "2", "3", "4", "5",
				"6", "7", "8", "9", "0", "1", "2", "3", "4", "5", "6", "7",
				"8", "9", "0", "1", "2", "3", "4", "5", "6", "7", "8", "9",
				"0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "0", "1",
				"2", "3", "4", "5", "6", "7", "8", "9", "0", "1" };
		// 定义随机数对象
		Random rnd = new Random();
		// 使用for循环生成随机数，使用随机数从数组中取出字符作为验证码
		for (int i = 0; i < 4; i++) {
			//每循环一次取出一个字符
			String cStr = code[rnd.nextInt(104)];
			//设置每一个输出的验证码的颜色
			graph.setColor(new Color(rnd.nextInt(125),rnd.nextInt(125),rnd.nextInt(125)));
			//设置输出验证码的字体
			graph.setFont(new Font("",Font.PLAIN,20+rnd.nextInt(5)));
			//绘制每一个验证码
			graph.drawString(cStr, 15*i+rnd.nextInt(5), 20-rnd.nextInt(5));
			//将每一个验证码添加到整体验证码中
			codeStr.append(cStr);
		}
		//定义验证码字符串
		String codeInfo = codeStr.toString();
		//将验证码放在session中
		request.getSession().setAttribute("code", codeInfo);
		//随机产生100个干扰点
		   for (int i = 0; i < 100; i++)
		   {
		    int x = rnd.nextInt(width);
		    int y = rnd.nextInt(height);
		    graph.setColor(new Color(rnd.nextInt(185)+40,rnd.nextInt(185)+40,rnd.nextInt(185)+40));
		    //设置干扰点的位置长宽
		    graph.drawOval(x, y, 1, 1);
		   }
		   //将图片输出到页面上
		   ImageIO.write(img, "JPEG", out);
		out.flush();
		out.close();