Ajax验证码（JSP+SERVLET）

servlet代码：

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.ServletOutputStream;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class ImageAction extends HttpServlet {
	/**
	 * 执行登陆的业务处理
	 * @param request:发送上来的请求
	 * @return destJsp：目标URL
	 */
	public void service(HttpServletRequest request,HttpServletResponse response) throws IOException,ServletException{
		//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(220,250));
		g.fillRect(0,width,height);
		//设定字体
		g.setFont(new Font("Times New Roman",Font.PLAIN,18));
		//画边框
		//g.drawRect(0,width-1,height-1);
		g.draw3DRect(0,height-1,true);
		//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(6位数字)
		String sRand = "";
		String s = "012345678901234567890123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ012345678901234567890123456789abcdefghijklmnopqrstuvwxyz";
		for (int i = 0; i < 4; i++) {
			char rand =s.charAt(random.nextInt(s.length()));
			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(String.valueOf(rand),13 * i + 6,16);
		}
		g.drawOval(0,12,60,11);
		// 将认证码存入SESSION
		request.getSession().setAttribute("rand",sRand);
		// 图象生效
		g.dispose();
		ServletOutputStream output;
		try {
			output = response.getOutputStream();
			// 输出图象到页面
			ImageIO.write(image,"JPEG",output);
		} catch (IOException e) {
			e.printStackTrace();
		}
	}
	
	/**
	 * 生成随机颜色
	 */
	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);
	}
}

web.xml代码

<servlet>
  <servlet-name>ImageAction</servlet-name>
  <servlet-class>cn.netjava.servlet.ImageAction</servlet-class>
  </servlet>
  <servlet-mapping>
  <servlet-name>ImageAction</servlet-name>
  <url-pattern>/ImageAction</url-pattern>
  </servlet-mapping>

index.HTML代码

<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd">
<html>
<head>
<Meta http-equiv="Content-Type" content="text/html; 

charset=UTF-8">
<title>验证码测试</title>

<script type="text/javascript">

//取得XMLHttpRequest对象是AJAX的要点
//此getXMLRequest()方法是根据不同浏览器来取得XMLHttpRequest对象
function getXMLRequest(){
	var request;
	try{
        //for火狐等浏览器
        request = new XMLHttpRequest();
	}catch(e){
        try{
            //for IE
            

request = new ActiveXObject("Microsoft.XMLHttp");  
        }catch(e){
            alert("您的浏览器不支持AJAX!!!");
            return null;
        }
	}
	return request;
}

//此checkcode()方法是更换验证码图片的要点
function checkcode(){
	var request = getXMLRequest();//得到XMLHttpRequest对象
	request.onreadystatechange = function(){
        if

(request.readyState == 4){
            document.getElementById("code").src = "ImageAction？"+Math.random();//改变验证码图片
        }
	}
                //将请求发送出去
	

request.open("GET","ImageAction",true);
	request.send(null);
}

</script>

</head>

<body>
//因为是单一功能测试，所以页面比较简单
//只有一个验证码的图片和一行字........
<img id="code" 

src="ImageAction"><br>
<a href="#" onclick="checkcode()">看不清，换一张</a>
</body>

</html>

Ajax验证码（JSP+SERVLET）

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