本文实例为大家分享了Java图片验证码代码，供大家参考，具体内容如下
网页显示效果:
index.jsp
使用两种方式强制图片更新：
1、设置图片输出时不缓存。
2、用js改变请求的地址。
<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> <html> <head> <title>第一个web项目的主页</title> <script type="text/javascript"> function changeImg(){ var _img=document.getElementById("_img"); var time=new Date().getTime();//浏览器认为相同的动作(被过滤)没必要应答,所以用时间值改变src值(即请求)(事实上是同一请求) _img.src="confirm"+time;//用js改变请求的地址 } </script> </head> <body> <h2>主页主页</h2> <h2>湖南长沙</h2> <h3>发布方式一......</h3> <img src="images/1.jpg"/> <br/> <a href="jsps/a.jsp">去到子页</a> <hr/> <form > 姓名:<input type="text" name="nmae"/><br/> 密码:<input type="password" name="pwd"/> <br/> 确认密码:<input type="text" name=pwd2/> <br/> 验证码:<input type="text" /><img id="_img" src="confirm"/> <!-- 不可行 <a href="confirm">看不清</a> <br/> --> <a href="javascript:changeImg();">看不清</a> <br/> <input type="submit" value="注册"/> </form> </body> </html>
自动生成验证码的java代码
关键类(以下类为基础部分的内容)
BufferedImage
ImageIO
Graphics/Graphics2D
import java.awt.Color; import java.awt.Font; import java.awt.Graphics; import java.awt.image.BufferedImage; 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; public class ImageServlet extends HttpServlet{ @Override protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException { // System.out.println("jinlaile"); resp.setContentType("image/jpeg");//jpeg是图片格式。设置响应内容的类型为jpeg的图片 int width=64; int height=40; BufferedImage bImg=new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); Graphics g=bImg.getGraphics(); //背景 g.setColor(Color.white); g.fillRect(0, 0, width, height); //字体颜色 g.setFont(new Font("aa", Font.BOLD,18)); //用随机数生成验证码:4个0~9以内的整数 Random r=new Random(); for(int i=0;i<=4;i++){ int t=r.nextInt(10);//10以内的随机整数 int y=10+r.nextInt(20);//上下位置:10~30 Color c=new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)); g.setColor(c); g.drawString(""+t, i*16, y); } //画干扰线 for(int i=1;i<8;i++){ Color c=new Color(r.nextInt(255), r.nextInt(255), r.nextInt(255)); g.setColor(c); g.drawLine(r.nextInt(width), r.nextInt(height), r.nextInt(width), r.nextInt(height)); } //把图形刷到bImg对象中 g.dispose();//相当于IO中的close()方法带自动flush(); ImageIO.write(bImg,"JPEG", resp.getOutputStream());//通过resp获取req的outputStream对象,发向客户端的socket的封装,即写到客户端 } }
web.xml
<"1.0" encoding="UTF-8"?> <web-app version="3.0" 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_3_0.xsd"> <display-name></display-name> <> <servlet> <servlet-name>bbbb</servlet-name> <jsp-file>/WEB-INF/b.jsp</jsp-file> </servlet> <> <servlet> <servlet-name>img</servlet-name> <servlet-class>cn.hncu.servlet.ImageServlet</servlet-class> </servlet> <servlet-mapping> <servlet-name>bbbb</servlet-name> <url-pattern>/bb.asp</url-pattern> </servlet-mapping> <servlet-mapping> <servlet-name>img</servlet-name> <url-pattern>/confirm</url-pattern> </servlet-mapping> <welcome-file-list> <welcome-file>index.jsp</welcome-file> </welcome-file-list> </web-app>