验证码 数字和大小写字母

在jsp页面：

<img  id="img" src="ImageServlet" onclick="javascript:this.src='ImageServlet?id='+  Math.random();" alt="换一个">	
<a href="javascript:reGetRandom();"><font size="2">换一张</font></a>

 

js：

//重新获得验证码
    function reGetRandom(){
    	var imge=document.getElementById("img");
    	//重新设置src属性，这里要注意ImageServlet后面带有一个随机的参数
    	imge.src="ImageServlet?seed="+Math.random();
    }

 

web.xml:

<servlet>
    <description>This is the description of my J2EE component</description>
    <display-name>This is the display name of my J2EE component</display-name>
    <servlet-name>ImageServlet</servlet-name>
    <servlet-class>cn.com.crystalnet.common.ImageServlet</servlet-class>
  </servlet>

  <servlet-mapping>
    <servlet-name>ImageServlet</servlet-name>
    <url-pattern>/ImageServlet</url-pattern>
  </servlet-mapping>

 

 

 

package cn.com.crystalnet.common;

import java.io.IOException;
import java.io.PrintWriter;

import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
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.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;

public class ImageServlet extends HttpServlet {

	/**
	 * title：产生验证码输入到JSP
	 * 
	 * @author 王立壮
	 * 
	 * @param request
	 *            the request send by the client to the server
	 * @param response
	 *            the response send by the server to the client
	 * @throws ServletException
	 *             if an error occurred
	 * @throws IOException
	 *             if an error occurred
	 */

	public char[] getRand() {
		char[] rand = new char[4];
		String str = "0123456789qwertyuioplkjhgfdsazxcvbnmQWERTYUIOPLKJHGFDSAZXCVBNM";
		for (int i = 0; i < 4; i++) {
			Random rd = new Random();
			int index = rd.nextInt(str.length());
			// 通过下标获取字符
			rand[i] = str.charAt(index);
		}
		return rand;
	}

	public Color getRandColor(int fc, int bc) {// 给定范围获得随机颜色

		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);

	}

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

		// 设置页面不缓存

		response.setHeader("Pragma", "No-cache");

		response.setHeader("Cache-Control", "no-cache");

		response.setDateHeader("Expires", 0);

		// 在内存中创建图象

		int width = 60, height = 20;

		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, 18));

		// 画边框

		// g.setColor(new Color());

		// g.drawRect(0,0,width-1,height-1);

		// 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 = "";
		char[] rand = this.getRand();
		System.out.println(new String(rand));
		for (int i = 0; i < 4; i++) {

			String r = Character.toString(rand[i]);

			sRand += r;

			// 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(r, 13 * i + 6, 16);

		}

		// 将认证码存入SESSION

		request.getSession().setAttribute("rand", sRand);

		// 图象生效

		g.dispose();

		// 输出图象到页面

		ImageIO.write(image, "JPEG", response.getOutputStream());

	}

	@Override
	protected void doPost(HttpServletRequest req, HttpServletResponse resp)
			throws ServletException, IOException {
		doGet(req, resp);
	}

}