                        课程
                    
                        /后端开发
                        
                            /Java
                        
                        /Java实现验证码制作

servlet验证码显示不出来

验证码显示一直是个×
index.jsp
<%@ page language="java" import="java.util.*" pageEncoding="gbk"%>
<%
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>My JSP 'index.jsp' starting page</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">
	<!--
	<link rel="stylesheet" type="text/css" href="styles.css">
	-->
	<script type="text/javascript">
		function reloadCode(){
			var time = new Date().getTime();
			document.getElementById("imagecode").src="<%=request.getContextPath() %>/servlet/ImageServlet?d="+time;
		}
	</script>
  </head>
  
  <body>
  <form action="<%=request.getContextPath() %>/servlet/LoginServlet" method="get">
    验证码：<input type="text" name="checkcode"/>
    <img alt="验证码" id="imagecode" src="<%=request.getContextPath() %>/servlet/ImageServlet"/>
    <a href="javascript: reloadCode();">看不清楚</a><br>
    <input type="submit" value="提交">
    </form>
  </body>
</html>

imageservlet.java

package com.CheckCode;

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.ServletException;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

public class ImageServlet extends HttpServlet {

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

//1.定义BufferedImage对象，参数(宽度，高度，图片类型)

BufferedImage bi = new BufferedImage(68, 22, BufferedImage.TYPE_INT_RGB);

//2.获得Graphics对象

Graphics g = bi.getGraphics();

//3.设置颜色

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

//4.把颜色给g对象

g.setColor(c);

//5.画框

g.fillRect(0, 0, 68, 22);

//6.指定验证码内容

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

//7.创建random随机对象获取验证码

Random r = new Random();

int len = ch.length; //获取ch长度

int index; //创建一个随机索引变量

StringBuffer sb = new StringBuffer(); //用于保存验证码的值

//通过循环随机取四位

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

index = r.nextInt(len);

//设置字符随机颜色

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

//设置字符随机位置

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

//将验证码添加到sb对象中

sb.append(ch[index]);

}

//将验证码保存到Session对象中，方便之后进行验证

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

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

}

protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

super.doPost(req, resp);

}

web.xml

<?xml version="1.0" encoding="UTF-8"?>

<web-app version="3.1" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd">

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

<servlet-class>com.CheckCode</servlet-class>

</servlet>

<servlet-mapping>

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

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

</servlet-mapping>

</web-app>