AJAX+jsp无刷新验证码实例

来源：作者：出处：巧巧读书 2007-07-19 进入讨论组

访问 http://www.qqread.com/j2ee/n244788.html

2,num.jsp,反馈xmlhttp请求的页面

<%@ page contentType="text/html; charset=GBK" language="java" import="java.sql.*" errorPage="" pageEncoding="GBK"%>
<%
//set Chinese Char
//Cody by JarryLi@gmail.com;

//homepage:jiarry.126.com
request.setCharacterEncoding("GBK");
response.setCharacterEncoding("GBK");
response.setContentType("text/html; charset=GBK");
%>
<%
String num=request.getParameter("num");
String random=(String)session.getAttribute("random");

if(num!=null&&random!=null)
{
if(!num.equals(random))
{
/*
out.println("<script>alert('验证码错误！请重试。')</script>");
out.println("<script>history.go(-1)</script>");
//response.sendRedirect("img.jsp");
*/
out.print("validate_failed:"+random);
}
else
{
//out.println("<center>验证成功！</center>");
out.print("validate_successful:"+random);
}
}
%>

3,random.jsp,生成验证码图片的页面
<%@ page autoFlush="false" import="java.util.*,java.awt.*,java.awt.image.*,com.sun.image.codec.jpeg.*,java.util.*" %>

<%
//set Chinese Char
//Cody by JarryLi@gmail.com;
//homepage:jiarry.126.com
request.setCharacterEncoding("GBK");
response.setCharacterEncoding("GBK");
response.setContentType("text/html; charset=GBK");
%>
<%
String chose="0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ";

char display[]={'0',' ','0',' ','0',' ','0'},ran[]={'0','0','0','0'},temp;

Random rand=new Random();

for(int i=0;i<4;i++)
{

temp=chose.charAt(rand.nextInt(chose.length()));

display[i*2]=temp;

ran[i]=temp;
}

String random=String.valueOf(display);

session.setAttribute("random",String.valueOf(ran));
%>
<%

        out.clear();
        response.setContentType("image/jpeg");
        response.addHeader("pragma","NO-cache");
        response.addHeader("Cache-Control","no-cache");
        response.addDateHeader("Expries",0);
        int width=80, height=30;
        BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics g = image.getGraphics();
        //以下填充背景颜色
        g.setColor(Color.GREEN);
        g.fillRect(0, 0, width, height);
       //设置字体颜色
        g.setColor(Color.RED);
        Font font=new Font("Arial",Font.PLAIN,20);
        g.setFont(font);
        //g.drawString(random,5,14);
        g.drawString(random,5,20);
        g.dispose();
        ServletOutputStream outStream = response.getOutputStream();
        JPEGImageEncoder encoder =JPEGCodec.createJPEGEncoder(outStream);
        encoder.encode(image);
        outStream.close();
   %>