验证码

今天搞了好长时间的验证码，终于弄好了

首先先创建validating.jsp，专门生成图片验证码

代码:

<%@ page language="java" contentType="text/html; charset=UTF-8"
    pageEncoding="UTF-8"%>
<%@ page import="java.util.Random"%>
<%@ page import="java.io.OutputStream"%>
<%@ page import="java.awt.Color"%>
<%@ page import="java.awt.Font"%>
<%@ page import="java.awt.Graphics"%>
<%@ page import="java.awt.image.BufferedImage"%>
<%@ page import="javax.imageio.ImageIO"%>
     <h1>hello</h1>
<%
int width = 60;
int height = 32;
//create the image
BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
Graphics g = image.getGraphics();
// set the background color
g.setColor(new Color(0xDCDCDC));
g.fillRect(0, 0, width, height);
// draw the border
g.setColor(Color.black);
g.drawRect(0, 0, width - 1, height - 1);
// create a random instance to generate the codes
Random rdm = new Random();
String hash1 = Integer.toHexString(rdm.nextInt());
// make some confusion
for (int i = 0; i < 50; i++) {
int x = rdm.nextInt(width);
int y = rdm.nextInt(height);
g.drawOval(x, y, 0, 0);
}
// generate a random code
String capstr = hash1.substring(0, 4);
//将生成的验证码存入session
session.setAttribute("validateCode", capstr);
g.setColor(new Color(0, 100, 0));
g.setFont(new Font("Candara", Font.BOLD, 24));
g.drawString(capstr, 8, 24);
g.dispose();
//输出图片
response.setContentType("image/jpeg");
out.clear();
out = pageContext.pushBody();
OutputStream strm = response.getOutputStream();
ImageIO.write(image, "jpeg", strm);
strm.close();
%>
一般将它放在webapp下，或者webroot下

使用${pageContext.request,contextPath}/validating.jsp可得到

在登录页面

  验证码：<img src="${pageContext.request.contextPath}/validating.jsp" id="yanzheng"/> 
   <a href="javascript:void(0);" οnclick="changge();">看不清 换一张 </a>

<script type="text/javascript">
function changge(){
var img=document.getElementById("yanzheng");
img.src=img.src+"?"; //意思是让图片重新加载一次 效果类似与直接刷新yanzhengma.jsp有了这个，就能让图片重新加载了
}