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' οnclick="btn.disabled=false;"/><input type="button" value="换一个" οnclick="reloadImage()" id='btn'></body>
</html>
运行结果：
