下面直接附上我的例子：
截图如下：
代码如下：
1.JAVA类：CodeServlet.java:
[java]
package cn.gov.csrc.servlet;
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.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 CodeServlet extends HttpServlet {
/**
* 产生验证码图片
*/
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("image/jpeg");
response.setHeader("Cache-Control", "no-cache");
response.setHeader("Pragma", "No-cache");
response.setDateHeader("Expires", 0L);
int width = 80;
int height = 30;
BufferedImage image = new BufferedImage(width, height, 1);
Graphics g = image.getGraphics();
Random random = new Random();
g.setColor(getRandColor(200, 250));
g.fillRect(0, 0, width, height);
g.setFont(new Font("Arial", 0, 25));
g.setColor(getRandColor(160, 200));
for (int i = 0; i < 155; i++) {
int x = random.nextInt(width + 100);
int y = random.nextInt(height + 100);
int xl = random.nextInt(10);
int yl = random.nextInt(12);
g.drawOval(x, y, x + xl, y + yl);
}
String code = request.getParameter("code");
String sRand = code;
for (int i = 0; i < sRand.length(); i++) {
String rand = sRand.substring(i, i + 1);
g.setColor(new Color(20 + random.nextInt(110), 20 + random
.nextInt(110), 20 + random.nextInt(110)));
g.drawString(rand, 14 * i + 5, 25);
}
g.dispose();
javax.servlet.ServletOutputStream imageOut = response.getOutputStream();
JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(imageOut);
encoder.encode(image);
}
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);
}
}
2.Web.xml文件：
[html]
<?xml version="1.0" encoding="UTF-8"?>
<web-app version="2.5" xmlns="http://java.sun.com/xml/ns/javaee"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://java.sun.com/xml/ns/javaee
http://java.sun.com/xml/ns/javaee/web-app_2_5.xsd">
<display-name></display-name>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>CodeServlet</servlet-name>
<servlet-class>cn.gov.csrc.servlet.CodeServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>CodeServlet</servlet-name>
<url-pattern>/CodeServlet</url-pattern>
</servlet-mapping>
</web-app>
[javascript]
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%>
<%
String path = request.getContextPath();
String basePath = request.getScheme() + "://"
+ request.getServerName() + ":" + request.getServerPort()
+ path + "/";
%>
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
<html>
<head>
<base href="<%=basePath%>">
<title>验证码测试</title>
<meta http-equiv="pragma" content="no-cache">
<meta http-equiv="cache-control" content="no-cache">
<meta http-equiv="expires" content="0">
<meta http-equiv="keywords" content="keyword1,keyword2,keyword3">
<meta http-equiv="description" content="This is my page">
<script language="javascript" type="text/javascript">
var code ; //在全局 定义验证码
function createCode(){
code = "";
var codeLength = 5;//验证码的长度
//所有候选组成验证码的字符，可以用中文
var selectChar = new Array(0,1,2,3,4,5,6,7,8,9,'A','B','C',
'D','E','F','G','H','I','J','K','L','M','N','O','P',
'Q','R','S','T','U','V','W','X','Y','Z','a','b','c',
'd','e','f','g','h','i','j','k','l','m','n','o','p',
'q','r','s','t','u','v','w','x','y','z');
for(var i=0;i<codeLength;i++){
var charIndex = Math.floor(Math.random()*60);
code +=selectChar[charIndex];
}
return code;
}
function validate (){
var inputCode = document.getElementById("vcode").value.toLowerCase();
if(inputCode.length <=0){
alert("请输入验证码！");
return false;
}
else if(inputCode != code.toLowerCase()){
alert("验证码输入错误！");
show();//刷新验证码
return false;
}else{
alert("^-^ OK");
return true;
}
}
function show(){
//显示验证码
document.getElementById("code").src="CodeServlet?code="+createCode();
}
window.onload = function() {
//document.οnlοad=show();
show();//页面加载时加载验证码
//这时无论在ie还是在firefox中，js没有加载完，页面的东西是不会被执行的；
}
</script>
</head>
<body>
<form οnsubmit="return validate();" action="" method="post">
<h3>jsp+js+servlet实现验证码</h3>
<br /> 用户名：<input type="text" name="" /><br /> 请输入验证码： <input
type="text" id="vcode" style="width: 60;" maxLength="5" /> <img
src="" id="code" /> <a href="#" mce_href="#"
οnclick="javascript:show();return false;">看不清,换一张!</a><br /> <input
type="submit" />
</form>
</body>
</html>