HttpServletResponse getOutputStream 点击超链接更换图片(需要js函数的配合)
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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 { @Override protected 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
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