JAVA 验证码

1:ImageServlet.java

import hotbox.smis.action.SessionControl;
import hotbox.smis.action.SessionObject;

import java.awt.Color;

import java.awt.Font;

import java.awt.Graphics;

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;

@SuppressWarnings("serial")
public class ImageServlet extends HttpServlet {

	public void doGet(HttpServletRequest request, HttpServletResponse response)

	throws ServletException, IOException {

		this.doPost(request, response);

	}

	// 生成数字和字母的验证码

	public void doPost(HttpServletRequest request, HttpServletResponse response)

	throws ServletException, IOException {

		BufferedImage img = new BufferedImage(68, 22,

		BufferedImage.TYPE_INT_RGB);

		// 得到该图片的绘图对象

		Graphics g = img.getGraphics();

		Random r = new Random();

		Color c = new Color(200, 150, 255);

		g.setColor(c);

		// 填充整个图片的颜色

		g.fillRect(0, 0, 68, 22);

		// 向图片中输出数字和字母

		StringBuffer sb = new StringBuffer();

		char[] ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".toCharArray();

		int index, len = ch.length;

		for (int i = 0; i < 4; i++) {
			index = r.nextInt(len);
			g
					.setColor(new Color(r.nextInt(88), r.nextInt(188), r
							.nextInt(255)));
			g.setFont(new Font("Arial", Font.BOLD | Font.ITALIC, 16));// 输出的字体和大小
			g.drawString("" + ch[index], (i * 15) + 3, 18);// 写什么数字，在图片的什么位置画
			sb.append(ch[index]);

		}
		SessionObject so = new SessionObject();
		so.setScope(new String[] {});
		so.setSessionObj(sb.toString());
		SessionControl.insertSessionObject("CURRENT_LOGIN_SAFECODE", so);
		ImageIO.write(img, "JPG", response.getOutputStream());

	}
}

2:web.xml

<!-- 实现验证码 -->
<servlet>
		<servlet-name>ImageServlet</servlet-name>
		<servlet-class>hotbox.smis.web.ImageServlet</servlet-class>
	</servlet>
	<servlet-mapping>
		<servlet-name>ImageServlet</servlet-name>
		<url-pattern>/servlet/ImageServlet</url-pattern>
	</servlet-mapping>

3:abc.jsp

<script>
function reloadVerifyCode(){
	   var timenow = new Date().getTime();
	   document.getElementById("safecode").src="<%=request.getContextPath()%>/servlet/ImageServlet?d="+timenow;
	   }
</script>
<img
		alt="验证码" id="safecode" style="height: 25px; cursor: pointer;"
		src="<%=request.getContextPath()%>/servlet/ImageServlet"
		onclick="reloadVerifyCode()"></img>