java实现图片验证码（java自动生成验证码图片）

java实现图片验证码（java自动生成验证码图片）

本文实例为大家分享了java实现图片验证码的具体代码，供大家参考，具体内容如下

目的:

2) 防止表单重复提交

生成验证码的要点:

1) 使用java代码生成图片对象

BufferedImage

2) 使用Random生成随机字符串

3) 将图片对象用

ImageIO.write(图片对象, "jpeg|png", 响应字节输出流)返回给客户端浏览器

验证验证码：

要点：

1) 将验证码文字存入session作用域

2) 表单提交时，对比session中的验证码和表单中的验证码

CaptchaUtils.java

package cn.seeker.utils;

import javax.imageio.ImageIO;

import java.awt.*;

import java.awt.image.BufferedImage;

import java.io.FileNotFoundException;

import java.io.FileOutputStream;

import java.io.IOException;

import java.io.OutputStream;

import java.util.*;

import java.util.List;

public class CaptchaUtil {

public static String [] fuhao = {"+","-","*","/"};

public static int num = 0;

//生成随机算式

public static String random(){

List list = new ArrayList();

Random ran = new Random();

int n1 = ran.nextInt(10);

int n2 = ran.nextInt(10);

String f = fuhao[ran.nextInt(fuhao.length)];

StringBuilder sb = new StringBuilder(4);

switch (f){

case "+":

num = n1+n2;

break;

case "-":

num =n1-n2;

break;

case "*":

num = n1*n2;

break;

case "/":

if(n2 == 0){

n2 = ran.nextInt(10)+1;

num = n1/n2;

}else{

num = n1/n2;

}

break;

}

sb.append(n1);

sb.append(f);

sb.append(n2);

sb.append("=");

return sb.toString();

}

public static void outputImage(String str, OutputStream os){

Random ran = new Random();

//创建图片对象

BufferedImage img = http://new BufferedImage(100,40, BufferedImage.TYPE_INT_RGB);

//获取画布

Graphics g = img.getGraphics();

//设置背景

g.setColor(Color.white);

g.fillRect(0,0,100,40);

//写字

g.setColor(Color.black);

g.setFont(new Font("微软雅黑",Font.PLAIN,30));

g.drawString(str,10,40);

//随机三条线

g.drawLine(ran.nextInt(100),ran.nextInt(40),

ran.nextInt(100),ran.nextInt(40));

g.drawLine(ran.nextInt(100),ran.nextInt(40),

ran.nextInt(100),ran.nextInt(40));

g.drawLine(ran.nextInt(100),ran.nextInt(40),

ran.nextInt(100),ran.nextInt(40));

// 4. 输出结果

// 常见的压缩格式：jpeg(有损压缩), png(无损压缩) ...

try {

ImageIO.write(img, "png", os);

} catch (IOException e) {

e.printStackTrace();

}

}

}

regist.jsp

<%--

Created by IntelliJ IDEA.

User: Administrator

Date: 2018/10/14

Time: 15:43

To change this template use File | Settings | File Templates.

--%>

<%@ page contentType="text/html;charset=UTF-8" language="java" %>

输入验证码：

CaptchaServlet.java

package cn.seeker.controller;

import cn.seeker.utils.CaptchaUtil;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

@WebServlet(urlPatterns = "/captcha.png")

public class CaptchaServlet extends HttpServlet {

@Override

protected void service(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {

response.setContentType("image/png");

//获取随机字符串

String random = CaptchaUtil.random();

//输出图片

CaptchaUtil.outputImage(random,response.getOutputStream());

//存入结果

request.getSession().setAttribute("res",CaptchaUtil.num);

}

}

registServlet.jsp

package cn.seeker.controller;

import javax.servlet.ServletException;

import javax.servlet.annotation.WebServlet;

import javax.servlet.http.HttpServlet;

import javax.servlet.http.HttpServletRequest;

import javax.servlet.http.HttpServletResponse;

import java.io.IOException;

@WebServlet(urlPatterns = "/regist")

public class registServlet extends HttpServlet {

@Override

protected void service(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {

String cap = req.getParameter("cap");

Integer res = (Integer)req.getSession().getAttribute("res");

if(Integer.parseInt(cap) == res) {

// 填写正确，注册成功

req.getSession().removeAttribute("res");

System.out.println("注册成功");

resp.sendRedirect("/index.jsp");

} else {

req.setAttribute("error", "验证码不正确");

req.getRequestDispatcher("/jsp/regist.jsp").forward(req,resp);

}

}

}

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