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                        /Java实现验证码制作

为什么按照教程写的一样不能显示验证码？是哪里错了吗？

//index.jsp

<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>

String path = request.getContextPath();

String basePath = request.getScheme()+"://"+request.getServerName()+":"+request.getServerPort()+path+"/";

<html>

<head>

function reloadCode(){

var time=new Date().getTime();

document.getElementById("imagecode").src="<%=request.getContextPath() %>/servlet/ImgeServlet?d="+time;

}

</script>

</head>

<body>

验证码：<input type="text" name="checkcode">

<img alt="验证码" id="imagecode" src="<%=request.getContextPath() %>/servlet/ImgeServlet"/>

</body>

</html>

//ImageServlet.java

package com.muke;

import java.awt.Color;

import java.awt.color.*;

import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.io.IOException;

import java.util.Random;

import javax.imageio.ImageIO;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class ImageServlet extends HttpServlet{

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

BufferedImage bi = new BufferedImage(80, 22, BufferedImage.TYPE_INT_RGB);

//画一个图片

Graphics g=bi.getGraphics();

Color c=new Color(200,150,255);

g.setColor(c);

g.fillRect(0, 0, 80, 22);

//背景图片内容

char[] ch="ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".toCharArray();

//随机获取四个字符

Random r=new Random();

int len=ch.length,index;

//定义一个

StringBuffer sb=new StringBuffer();

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

index=r.nextInt(len);

//随机颜色

g.setColor(new Color(r.nextInt(88),r.nextInt(188),r.nextInt(255)));

//将字符画到图片上

g.drawString(ch[index]+"", (i*15)+3, 18);

//将字符保存起来

sb.append(ch[index]);

}

//将字符保存在

request.getSession().setAttribute("piccode", sb.toString());

//进行输出

ImageIO.write(bi,"JPG",response.getOutputStream());

}

//web.xml

<?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">

<servlet-name>ImageServlet</servlet-name>

<servlet-class>com.muke.ImageServlet</servlet-class>

</servlet>

<servlet-mapping>

<servlet-name>ImageServlet</servlet-name>

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

</servlet-mapping>

<welcome-file-list>

<welcome-file>index.jsp</welcome-file>

</welcome-file-list>

<login-config>

<auth-method>BASIC</auth-method>