前言：
为了防止用户恶意,或者使用软件外挂提交一些内容,就得用验证码来阻止,虽然这个会影响用户体验,但为了避免一些问题很多网站都使用了验证码;今天下午参 考文档弄了一个验证码,这里分享一下;这是一个web工程,首先是页面,这里只是一个显示验证码页面index.jsp,使用默认生成的就可以了,表单没 有做提交,如下：
<%@ page language="java" import="java.util.*" pageEncoding="UTF-8"%> <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
下面是后台代码,这里是一个Servlet,不要忘记在web.xml中配置请求url：
package com.wf.web;
import java.io.IOException;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;public class ImageServlet extends HttpServlet { private static final long serialVersionUID = 1L; public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("image/jpeg");//设置相应类型,告诉浏览器输出的内容为图片
response.setHeader("Pragma", "No-cache");//设置响应头信息，告诉浏览器不要缓存此内容
response.setHeader("Cache-Control", "no-cache");
response.setDateHeader("Expire", 0);
RandomValidateCode randomValidateCode = new RandomValidateCode(); try {
randomValidateCode.getRandcode(request, response);//输出图片方法
} catch (Exception e) {
e.printStackTrace();
}
} public void doPost(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
doGet(request, response);
}
}这个类是生成验证码的方法,如下：
package com.wf.web;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.util.Random;
import javax.imageio.ImageIO;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;public class RandomValidateCode { public static final String RANDOMCODEKEY = "RANDOMVALIDATECODEKEY";//放到session中的key
private Random random = new Random(); private String randString = "0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";//随机产生的字符串
private int width = 80;//图片宽
private int height = 26;//图片高
private int lineSize = 40;//干扰线数量
private int stringNum = 4;//随机产生字符数量
/*
* 获得字体 */
private Font getFont(){ return new Font("Fixedsys",Font.CENTER_BASELINE,18);
} /*
* 获得颜色 */
private Color getRandColor(int fc,int bc){ if(fc > 255)
fc = 255; if(bc > 255)
bc = 255; int r = fc + random.nextInt(bc-fc-16); int g = fc + random.nextInt(bc-fc-14); int b = fc + random.nextInt(bc-fc-18); return new Color(r,g,b);
} /**
* 生成随机图片 */
public void getRandcode(HttpServletRequest request,
HttpServletResponse response) {
HttpSession session = request.getSession(); //BufferedImage类是具有缓冲区的Image类,Image类是用于描述图像信息的类
BufferedImage image = new BufferedImage(width,height,BufferedImage.TYPE_INT_BGR);
Graphics g = image.getGraphics();//产生Image对象的Graphics对象,改对象可以在图像上进行各种绘制操作
g.fillRect(0, 0, width, height);
g.setFont(new Font("Times New Roman",Font.ROMAN_BASELINE,18));
g.setColor(getRandColor(110, 133)); //绘制干扰线
for(int i=0;i<=lineSize;i++){
drowLine(g);
} //绘制随机字符
String randomString = ""; for(int i=1;i<=stringNum;i++){
randomString=drowString(g,randomString,i);
}
session.removeAttribute(RANDOMCODEKEY);
session.setAttribute(RANDOMCODEKEY, randomString);
System.out.println(randomString);
g.dispose(); try {
ImageIO.write(image, "JPEG", response.getOutputStream());//将内存中的图片通过流动形式输出到客户端
} catch (Exception e) {
e.printStackTrace();
}
} /*
* 绘制字符串 */
private String drowString(Graphics g,String randomString,int i){
g.setFont(getFont());
g.setColor(new Color(random.nextInt(101),random.nextInt(111),random.nextInt(121)));
String rand = String.valueOf(getRandomString(random.nextInt(randString.length())));
randomString +=rand;
g.translate(random.nextInt(3), random.nextInt(3));
g.drawString(rand, 13*i, 16); return randomString;
} /*
* 绘制干扰线 */
private void drowLine(Graphics g){ int x = random.nextInt(width); int y = random.nextInt(height); int xl = random.nextInt(13); int yl = random.nextInt(15);
g.drawLine(x, y, x+xl, y+yl);
} /*
* 获取随机的字符 */
public String getRandomString(int num){ return String.valueOf(randString.charAt(num));
}
}这里附带吧web.xml也加上吧,希望对初学者有帮助
<?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"> ImageServlet<servlet-class>com.wf.web.ImageServletclass>ImageServlet/imageServletindex.jsp
就这么多,验证码是保存在session中的,或者cookie也行,但都要必须及时清除。
