在Servlet中，设置响应正文的类型为image/jpeg，表示响应的是一个图片，然后通过java.awt包中的操作图形图像的类来生成一个图像
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java.awt.image.BufferedImage：创建该对象时，会在缓存中构造一个图像
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java.awt.Graphics：该类的对象表示一个画笔，用来话矩形，写字，添加颜色
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java.util.Random：该类的对象用于生成随机输
新建ValidateCodeServlet类public class ValidateCodeServlet extends HttpServlet {
/** * Constructor of the object. */ public ValidateCodeServlet() { super(); } /** * Destruction of the servlet. <br> */ public void destroy() { super.destroy(); // Just puts "destroy" string in log // Put your code here } /** * The doGet method of the servlet. <br> * * This method is called when a form has its tag value method equals to get. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { this.doPost(request, response); } /** * The doPost method of the servlet. <br> * * This method is called when a form has its tag value method equals to post. * * @param request the request send by the client to the server * @param response the response send by the server to the client * @throws ServletException if an error occurred * @throws IOException if an error occurred */ public Color getRandomColor(int fc,int bc){ Random random = new Random(); Color randomColor = null; if(fc>255) fc=255; if(bc>255) bc=255; //设置个0-255之间的随机颜色值 int r=fc+random.nextInt(bc-fc); int g=fc+random.nextInt(bc-fc); int b=fc+random.nextInt(bc-fc); randomColor = new Color(r,g,b); return randomColor;//返回具有指定红色、绿色和蓝色值的不透明的 sRGB 颜色 } public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException { //禁止页面缓存 response.setHeader("Pragma", "No-cache"); response.setHeader("Cache-Control", "No-cache"); response.setDateHeader("Expires", 0); response.setContentType("image/jpeg"); //设置响应正文的MIME类型为图片 int width=60, height=20; /**创建一个位于缓存中的图像，宽度60，高度20 */ BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Graphics g = image.getGraphics(); //获取用于处理图形上下文的对象，相当于画笔 Random random = new Random(); //创建生成随机数的对象 g.setColor(getRandomColor(200,250)); //设置图像的背景色 g.fillRect(0, 0, width, height); //画一个矩形 ，坐标（0，0），宽度60，高度20 g.setFont(new Font("Times New Roman",Font.PLAIN,18)); //设定字体格式 g.setColor(getRandomColor(160,200)); for(int i=0;i<130;i++){ //产生130条随机干扰线 int x = random.nextInt(width); int y = random.nextInt(height); int xl = random.nextInt(12); int yl = random.nextInt(12); g.drawLine(x,y,x+xl,y+yl); //在图象的坐标（x,y）和坐标（x+x1,y+y1）之间画干扰线 } String strCode=""; for (int i=0;i<4;i++){ String strNumber=String.valueOf(random.nextInt(10)); //把随机数转换成String字符串 strCode=strCode+strNumber; //设置字体的颜色 g.setColor(new Color(15+random.nextInt(120),15+random.nextInt(120),15+random.nextInt(120))); g.drawString(strNumber,13*i+6,16); //将验证码依次画到图像上,坐标（x=13*i+6,y=16） } request.getSession().setAttribute("Code",strCode); //把验证码保存到Session中 g.dispose(); //释放此图像的上下文以及它使用的所有系统资源 ImageIO.write(image, "JPEG", response.getOutputStream()); //输出JPEG格式的图像 response.getOutputStream().flush(); //刷新输出流 response.getOutputStream().close(); //关闭输出流 } /** * Initialization of the servlet. <br> * * @throws ServletException if an error occurs */ public void init() throws ServletException { // Put your code here }}
index.jsp页面
<%@ 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>用户注册</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">
-->
<style type="text/css">
table{
font-size:12px;
font-family: 隶书;
color:gray;
border: 1px green solid;
}
input{
font-size:12px;
font-family: 隶书;
color:gray;
}
</style>
</head>
<body>
<form action="" method="post">
<table align="center">
<tr>
<td>用户名：</td>
<td><input type="text" name="name" /></td>
</tr>
<tr>
<td>密码：</td>
<td><input type="password" name="pwd" /></td>
</tr>
<tr>
<td>性别：</td>
<td>
<input type="radio" name="sex" value="男" />男
<input type="radio" name="sex" value="女" />女
</td>
</tr>
<tr>
<td>年龄：</td>
<td><input type="text" name="age" /></td>
</tr>
<tr>
<td>Email：</td>
<td><input type="text" name="email" /></td>
</tr>
<tr>
<td>验证码：</td>
<td>
<img alt="" src="validatecode" >
</td>
</tr>
<tr>
<td>输入验证码：</td>
<td>
<input type="text" name="code"/>
</td>
</tr>
<tr>
<td colspan="2" align="center">
<input type="submit" value="注 册" />
<input type="reset" value="重 置" />
</td>
</tr>
</table>
</form>
</body>
</html>
web.xml文件配置
<servlet>
<description>This is the description of my J2EE component</description>
<display-name>This is the display name of my J2EE component</display-name>
<servlet-name>ValidateCodeServlet</servlet-name>
<servlet-class>com.lh.servlet.ValidateCodeServlet</servlet-class>
</servlet>
<servlet-mapping>
<servlet-name>ValidateCodeServlet</servlet-name>
<url-pattern>/validatecode</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>