礼悟：
好好学习合思考，尊师重道存感恩。叶见寻根三返一，江河湖海同一体。
虚怀若谷良心主，愿行无悔给最苦。读书锻炼强身心，诚劝且行且珍惜。
javaEE：7
javaSE：1.8
JSTL：1.2.2
server：tomcat 8.5
browser：Chrome/Firefox
os：windows7 x64
ide：MyEclipse 2017
工程目录结构
web.xml
<?xml version="1.0" encoding="UTF-8"?><web-app xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns="http://xmlns.jcp.org/xml/ns/javaee" xsi:schemaLocation="http://xmlns.jcp.org/xml/ns/javaee http://xmlns.jcp.org/xml/ns/javaee/web-app_3_1.xsd" id="WebApp_ID" version="3.1"> ?<display-name>Day12</display-name> ?<welcome-file-list> ???<welcome-file>index.html</welcome-file> ???<welcome-file>index.htm</welcome-file> ???<welcome-file>index.jsp</welcome-file> ???<welcome-file>default.html</welcome-file> ???<welcome-file>default.htm</welcome-file> ???<welcome-file>default.jsp</welcome-file> ?</welcome-file-list> ?????<servlet> ?<servlet-name>VerifyCodeServlet</servlet-name> ?<servlet-class>com.jizuiku.servlet.VerifyCodeServlet</servlet-class> ?</servlet> ???<servlet-mapping> ?<servlet-name>VerifyCodeServlet</servlet-name> ?<url-pattern>/VerifyCodeServlet</url-pattern> ?</servlet-mapping> ?</web-app>
Servlet类代码
package com.jizuiku.servlet;import java.awt.Color;import java.awt.Font;import java.awt.Graphics2D;import java.awt.image.BufferedImage;import java.io.FileOutputStream;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;/** * ?* ?* @author 博客园-给最苦 * @version V2017.11.30 */public class VerifyCodeServlet extends HttpServlet {@Overrideprotected void doGet(HttpServletRequest req, HttpServletResponse response) throws ServletException, IOException {// 这个代码是需要优化的，生成图片的代码可以整合为一个工具类int width = 100;int height = 50;int imageType = BufferedImage.TYPE_INT_BGR;BufferedImage myImage = new BufferedImage(width, height, imageType);Graphics2D pen = (Graphics2D) myImage.getGraphics();pen.setColor(Color.WHITE);pen.fillRect(0, 0, 100, 50);Font font = new Font("微软雅黑", 2, 25);pen.setFont(font);pen.setColor(Color.blue);pen.drawString(Integer.toString(new Random().nextInt(100)), 20, 35);// ????????????????????????????重点！response.getOutputStream();ImageIO.write(myImage, "JPEG", response.getOutputStream());}}
index.jsp
<%@ 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>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 _change() {var img = document.getElementById("pictureImg");// new Date().getTime() 因为缓存而生img.setAttribute("src", "/Day12/VerifyCodeServlet?time=" + new Date().getTime());}</script></head><body><img id="pictureImg" src="/Day12/VerifyCodeServlet" /><a href="javascript:_change()">换一换</a></body></html>浏览器查看index.jsp页面
点击超链接，换一张看看
学习资源：itcast和itheima视频库。如果您有公开的资源，可以分享给我的话，用您的资源学习也可以。
博文是观看视频后，融入思考写成的。博文好，是老师讲得好。博文坏，是 给最苦 没认真。
HttpServletResponse getOutputStream 点击超链接更换图片(需要js函数的配合)
原文地址：http://www.cnblogs.com/jizuiku/p/7993273.html