java部分
package com.servlet; import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.PrintWriter;
import java.util.Random; import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
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 IdentityServlet extends HttpServlet {
//不包括0，O，1，I等难以辨认的字符
public static final char[] CHARS={'2','3','4','5','6','7','8','9','A','B','C','D','E','F','G','H','I','J','K','L','M','N','P','Q','R','S','T','U','V','W','X','Y','Z'}; public static Random random=new Random();
//获取随机码
public static String getRandomString(){
StringBuffer buffer=new StringBuffer();
for(int i=0;i<6;i++){
buffer.append(CHARS[random.nextInt(CHARS.length)]);
}
return buffer.toString();
}
//获取随机颜色
public static Color getRandomColor(){
return new Color(random.nextInt(255),random.nextInt(255),random.nextInt(255));
}
//获取所给颜色的相反值
public static Color getReverseColor(Color c){
return new Color(255-c.getRed(),255-c.getGreen(),255-c.getBlue());
} public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { response.setContentType("image/jpeg");//设置输出类型
String randomString=getRandomString();//获取随机数
request.getSession(true).setAttribute("randomString", randomString);//将随机数放入session中
int width=100;//图片宽度
int height=30;//图片高度 Color color=getRandomColor();//获取颜色，用于背景色
Color reverse=getReverseColor(color);//发色，用于前背景 BufferedImage bi=new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);//创建一个彩色图片 Graphics2D g=bi.createGraphics();//获取绘图对象
g.setFont(new Font(Font.SANS_SERIF,Font.BOLD,16));//设置字体
g.setColor(color);//设置颜色
g.fillRect(0, 0, width, height);//绘制背景
g.setColor(reverse);
g.drawString(randomString, 18, 20);//设置颜色 //绘制遭点
for(int i=0, n=random.nextInt(50);i<n;i++){
g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);
}
ServletOutputStream out=response.getOutputStream();
JPEGImageEncoder encoder=JPEGCodec.createJPEGEncoder(out);
encoder.encode(bi);
out.flush(); } public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException { } }
web.xml部分
<?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> <servlet>
<servlet-name>IdentityServlet</servlet-name>
<servlet-class>com.servlet.IdentityServlet</servlet-class>
</servlet> <servlet-name>IdentityServlet</servlet-name>
<url-pattern>/servlet/IdentityServlet</url-pattern>
</servlet-mapping>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
</web-app>
html部分
<%@ 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>
<script type="text/javascript">
function reloadImage(){
document.getElementById('btn').disabled=true;
document.getElementById('identity').src='servlet/IdentityServlet?ts='+new Date().getTime();
}
</script>
</head> <body>
<img src="servlet/IdentityServlet" id='identity' onclick="btn.disabled=false;"/>
<input type="button" value="换一个" onclick="reloadImage()" id='btn'>
</body>
</html>
运行结果：