【原创】Strtus实现验证码

1.CheckCode 生成验证码类

package com.zwj.tools;

import javax.servlet.http.HttpServlet;
import java.io.*;
import javax.servlet.*;
import javax.servlet.http.*;
import java.awt.*;
import java.awt.image.*;
import javax.imageio.ImageIO;

/**
 * 模块功能: 生成验证码
 */
@SuppressWarnings("serial")
public class CheckCode extends HttpServlet {
	private static int WIDTH = 60;
	private static int HEIGHT = 25;

	public void doGet(HttpServletRequest request, HttpServletResponse response) {
		try {
			HttpSession session = request.getSession();
			response.setContentType("image/jpeg");
			ServletOutputStream sos = response.getOutputStream();
			// 设置浏览器不要缓存此图片
			response.setHeader("Pragma", "No-cache");
			response.setHeader("Cache-Control", "no-cache");
			response.setDateHeader("Expires", 0);
			// 创建内存图象并获得其图形上下文
			BufferedImage image = new BufferedImage(WIDTH, HEIGHT,
					BufferedImage.TYPE_INT_RGB);
			Graphics g = image.getGraphics();
			// 产生随机的认证码
			char[] rands = generateCheckCode();
			// 产生图像
			drawBackground(g);
			drawRands(g, rands);
			// 结束图像 的绘制 过程， 完成图像
			g.dispose();
			// 将图像输出到客户端
			ByteArrayOutputStream bos = new ByteArrayOutputStream();
			ImageIO.write(image, "JPEG", bos);
			byte[] buf = bos.toByteArray();
			response.setContentLength(buf.length);
			// 下面的语句也可写成： bos.writeTo(sos);
			sos.write(buf);
			bos.close();
			sos.close();
			// 将当前验证码存入到 Session 中
			session.setAttribute("check_code", new String(rands));
			// 直接使用下面的代码将有问题， Session 对象必须在提交响应前获得
			// request.getSession().setAttribute("check_code",new
			// String(rands));
		} catch (Exception e) {
			e.printStackTrace();
		}
	}

	/**
	 * 定义验证码的字符表
	 * 
	 * @return
	 */
	private char[] generateCheckCode() {
		String chars = "123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";
		char[] rands = new char[4];
		for (int i = 0; i < 4; i++) {
			int rand = (int) (Math.random() * 61);
			rands[i] = chars.charAt(rand);
		}
		return rands;
	}

	/**
	 * 划出随机数值
	 * 
	 * @param
	 * @param rands
	 */
	private void drawRands(Graphics g, char[] rands) {
		g.setColor(Color.BLUE);
		g.setFont(new Font(null, Font.PLAIN | Font.PLAIN, 18));
		g.drawString("" + rands[0], 1, 17);
		g.drawString("" + rands[1], 16, 15);
		g.drawString("" + rands[2], 31, 18);
		g.drawString("" + rands[3], 46, 16);
		// System.out.println(rands);
	}

	/**
	 * 画图片背景
	 * 
	 * @param g
	 */
	private void drawBackground(Graphics g) {
		g.setColor(new Color(0xDCDCDC));
		g.fillRect(0, 0, WIDTH, HEIGHT);
		// 随机产生 120 个干扰点
		for (int i = 0; i < 120; i++) {
			int x = (int) (Math.random() * WIDTH);
			int y = (int) (Math.random() * HEIGHT);
			int red = (int) (Math.random() * 255);
			int green = (int) (Math.random() * 255);
			int blue = (int) (Math.random() * 255);
			g.setColor(new Color(red, green, blue));
			g.drawOval(x, y, 1, 0);
		}
	}

	/**
	 * 验证用户输入的验证码
	 * 
	 * @param request
	 * @param response
	 * @return
	 */
	public static boolean checkLook(HttpServletRequest request,
			HttpServletResponse response, String check) {
		response.setContentType("text/html;charset=GB2312");
		try {
			// PrintWriter out = response.getWriter();
			HttpSession session = request.getSession(false);
			check = check.toLowerCase(); // 把用户输入的验证码转换成小写
			if (session == null)
				return false;
			String savedCode = (String) session.getAttribute("check_code");
			savedCode = savedCode.toLowerCase(); // 把存到session里的值转换成小写
			if (savedCode == null)
				return false;
			if (!savedCode.equals(check))
				return false;
		} catch (Exception e) {
			e.printStackTrace();
		}
		return true;
	}
}

2. 配置web.xml

    <!-- 验证码 -->
    <servlet> 
    	<servlet-name>CheckCode</servlet-name> 
    	<servlet-class>com.zwj.tools.CheckCode</servlet-class> 
  </servlet> 
  <servlet-mapping> 
    	<servlet-name>CheckCode</servlet-name> 
    	<url-pattern>/CheckCode</url-pattern> 
  </servlet-mapping> 

3. 在action用调用验证码类

// 验证用户输入的验证码
if (CheckCode.checkLook(request, response, validateChar)) {

             System.out.println("验证码成功！");
/**
* 当用户操作成功后，注意把session中的验证码清空: 这样可以防止用户不停的做某个操作.
 **/
    request.getSession(false).removeAttribute("check_code");

}else
{
	   System.out.println("验证码错误！");
	   return mapping.getInputForward();
}

4. jsp页面的显示

         验证码：<img align="middle" src="CheckCode" />