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建立一个web工程
编写servlet,生成图像
package com.imooc; import java.awt.Color; import java.awt.Graphics; import java.awt.image.BufferedImage; import java.io.IOException; import java.util.Random; import javax.imageio.ImageIO; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class ImageSevlet extends HttpServlet { public void doGet(HttpServletRequest request,HttpServletResponse response) throws IOException { System.err.println("doget into"); BufferedImage bi = new BufferedImage(68, 22, BufferedImage.TYPE_INT_RGB); //画图 Graphics g = bi.getGraphics(); Color c = new Color(200,150,255); g.setColor(c); g.fillRect(0, 0, 68, 22);//画背景 //画验证码图片里面的内容 char[] ch = "ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789".toCharArray(); Random r = new Random(); //获取随机的4个类 int len = ch.length, index;//len-1是ch下标的取值上限 StringBuffer sb = new StringBuffer(); for(int i = 0; i < 4 ; i++) { index = r.nextInt(len); //获取随机位置,即获取到了字符 //,new 一个新的颜色,不让字符的颜色一致,随机取, g.setColor(new Color(r.nextInt(88),r.nextInt(188),r.nextInt(255)));//随机颜色 //画在图片上,位置 g.drawString(ch[index]+"", (i*15)+3, 18); //保存生成的字符 sb.append(ch[index]); } //放在session中 request.getSession().setAttribute("verifyCode", sb.toString()); //输出到response中,write(RenderedImage im, String formatName, OutputStream output) ImageIO.write(bi, "jpg", response.getOutputStream()); } }
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>verifyCode</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> <description></description> <display-name>ImageSevlet</display-name> <servlet-name>ImageSevlet</servlet-name> <servlet-class>com.imooc.ImageSevlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>ImageSevlet</servlet-name> <url-pattern>/servlet/ImageSevlet</url-pattern> </servlet-mapping> </web-app>
jsp
<%@ page language="java" contentType="text/html; charset=UTF-8" pageEncoding="UTF-8"%> <% String nameSpace = request.getContextPath(); %> <% String projectPath = request.getScheme() + "://" + request.getServerName() + ":" + request.getServerPort() + nameSpace + "/"; %> <%--以后可以在页面直接使用$("basepath") --%> <%-- <c:set value="<%=projectPath %>" var="basePath"/> --%> <!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN" "http://www.w3.org/TR/html4/loose.dtd"> <html> <head> <meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> <title>Insert title here</title> <script type="text/javascript"> function reloadCode() { //解决缓存的问题 var time = new Date().getTime(); //在路径后面加上时间是因为这样每次请求的url不一样,浏览器就不会缓存,如果有缓存的影响那么图片就不会刷新 document.getElementById("verifyCode").src="<%=projectPath %>servlet/ImageSevlet?id="+time; } </script> </head> <body> 验证码:<input type="text" name = "verifyCode"/> <img id="verifyCode" src="<%=projectPath %>servlet/ImageSevlet" alt="verifyCode"> <a href="javascript:reloadCode();"> 看不清,刷新</a> <br> </body> </html>
效果(把浏览器放大了的效果)
后台验证
package com.imooc; import java.io.IOException; import java.io.PrintWriter; import javax.servlet.ServletException; import javax.servlet.http.HttpServlet; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; public class LoginServlet extends HttpServlet { @Override public void doGet(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { String verifyCode = (String) req.getSession().getAttribute("verifyCode"); String code = req.getParameter("verifyCode"); System.out.println(verifyCode); System.out.println(code); System.out.println(verifyCode.equalsIgnoreCase(code)); //设置页面类型,解决中文乱码的问题 resp.setContentType("text/html;charset=gbk"); PrintWriter out = resp.getWriter(); if(verifyCode.equalsIgnoreCase(code)) { out.print("success"); } else { out.print("false"); } } }
在web.xml中加入servlet
<servlet> <description></description> <servlet-name>LoginServlet</servlet-name> <servlet-class>com.imooc.LoginServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>LoginServlet</servlet-name> <url-pattern>/servlet/LoginServlet</url-pattern> </servlet-mapping>
修改上面的jsp,实际就是加入了form
<form action="<%=projectPath %>servlet/LoginServlet" method="get"> 验证码:<input type="text" name = "verifyCode"/> <img id="verifyCode" src="<%=projectPath %>servlet/ImageSevlet" alt="verifyCode"> <a href="javascript:reloadCode();"> 看不清,刷新</a> <br> <input type="submit" value="submit"> </form>
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原文地址：http://www.cnblogs.com/rocky-AGE-24/p/5932619.html
