JavaWeb用户信息管理系统-在登录中添加验证码功能

1 验证码生成的servlet

@WebServlet("/validateCode.do")
public class ValidateCodeServlet extends HttpServlet {

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

		// 在内存中创建图象
		int width = 70, height = 45;
		BufferedImage image = new BufferedImage(width, height,
				BufferedImage.TYPE_INT_RGB);
		// 获取图形上下文
		Graphics g = image.getGraphics();
		// 生成随机类
		Random random = new Random();
		// 设定背景色
		g.setColor(getRandColor(200, 250));
		g.fillRect(0, 0, width, height);
		// 设定字体
		g.setFont(new Font("Times New Roman", Font.PLAIN, 20));
		// 随机产生155条干扰线，使图象中的认证码不易被其它程序探测到
		g.setColor(getRandColor(160, 200));
		for (int i = 0; i < 155; i++) {
			int x = random.nextInt(width);
			int y = random.nextInt(height);
			int xl = random.nextInt(12);
			int yl = random.nextInt(12);
			g.drawLine(x, y, x + xl, y + yl);
		}
		// 取随机产生的认证码(4位数字)
		String sRand = "";
		for (int i = 0; i < 4; i++) {
			String rand = String.valueOf(random.nextInt(10));
			sRand += rand;
			// 将认证码显示到图象中
			g.setColor(new Color(20 + random.nextInt(110), 20 + random
					.nextInt(110), 20 + random.nextInt(110)));
			// 调用函数出来的颜色相同，可能是因为种子太接近，所以只能直接生成
			g.drawString(rand, 13 * i + 6, 16);
		}
		// 图象生效
		g.dispose();
		
		try {
			ImageIO.write(image, "JPEG", response.getOutputStream());
		} catch (Exception e) {
			System.out.println("验证码图片产生出现错误：" + e.toString());
		}
		//保存验证码到Session
		request.getSession().setAttribute(Constants.VALIDATE_CODE_KEY, sRand);
		
	}


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

		this.doGet(request, response);
	}
	/*
	 * 给定范围获得随机颜色
	 */
	private Color getRandColor(int fc, int bc) {
		Random random = new Random();
		if (fc > 255)
			fc = 255;
		if (bc > 255)
			bc = 255;
		int r = fc + random.nextInt(bc - fc);
		int g = fc + random.nextInt(bc - fc);
		int b = fc + random.nextInt(bc - fc);
		return new Color(r, g, b);
	}
}

2 验证码标签

<span>
<input name="code" type="text" value="验证码" onclick="JavaScript:this.value=''"/>
</span>
<cite>
<img id="code" src="validateCode.do" onclick="change()">
</cite>

3 修改以前的filter，因为拦截了/validateCode.do

if(uri.indexOf("login.jsp") != -1 || uri.indexOf("login.do") != -1|| uri.indexOf("validateCode.do") != -1)

进行放行，因为验证码是login内嵌，必须展示出来的不能进行拦截。

4 效果