javaweb achieve image verification code, and verify operation

First we have to draw good from the server code, and then spread to the foreground by means of the stream, and then pass over the foreground and background verification code generated verification code to verify. Code is to prevent some of the robots operate as a means
not much to say, the following code first to generate it, here I made a generated code package

/**
 * Copyright (C), 2018-2019, XXX有限公司
 * FileName: ImageCode
 * Author:   1543057945
 * Date:     2019/1/11 17:18
 * Description:
 * History:
 * <author>          <time>          <version>          <desc>
 * 张良敏         修改时间           版本号              描述
 */
package Utils;

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.font.ImageGraphicAttribute;
import java.awt.image.BufferedImage;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.Random;
import java.util.concurrent.CountDownLatch;

/**
 * 〈一句话功能简述〉<br> 
 * 〈〉
 *
 * @author 1543057945
 * @create 2019/1/11
 * @since 1.0.0
 */
public class ImageCode {
    //验证码个数
     private int count=4;
    //验证码宽度，且设置每个字的宽度
     private int width=count*50;
    //验证码高度
     private int height=50;
    //图片验证码key
     private String code="";
    public ImageCode() {
    }
    public ImageCode(int count, int width, int height) {
        this.count = count;
        this.width = width;
        this.height = height;
    }
    public int getCount() {
        return count;
    }
    public String getCode() {
        return code;
    }
    public int getWidth() {
        return width;
    }
    public int getHeight() {
        return height;
    }
    public void setCount(int count) {
        this.count = count;
        width=this.count*50;
    }

    public void setWidth(int width) {
        this.width = width;
    }

    public void setHeight(int height) {
        this.height = height;
    }
    //测试写入
    public static void main(String[] args){
        long startend=System.currentTimeMillis();
        ImageCode imageCode=new ImageCode();
        //默认验证码位数为4，我这里设为5
        imageCode.setCount(5);
        //得到缓冲区
        BufferedImage image = imageCode.getImage();
        //得到真实验证码
        String code=imageCode.getCode();
        long endTime=System.currentTimeMillis();
        System.out.println("验证码为："+code+"\n花费时间为："+(endTime-startend)+"\n到E盘根目录下看，文件名为11.jpg");
    }
    public BufferedImage getImage(){
        //图片缓冲区
        BufferedImage image = new BufferedImage(width,height,1);
        //获得笔
        Graphics graphics = image.getGraphics();
        //设置初始画笔为白色
        graphics.setColor(new Color(255,255,254));
        //画满整个图，也就是把图片先变为白色
        graphics.fillRect(0,0,width,height);
        Random rd=new Random();
        //设置字体
        Font font=new Font("宋体",Font.PLAIN,35+rd.nextInt(10));
        graphics.setFont(font);
        char[] chars="qweCRYHrtasdfBxy678934VTGopNUFKuighjklzSXEDLOP12cvbnmQAZWJMI50".toCharArray();
        //画验证码
        for (int i = 0; i <count ; i++) {
            String string="";
            string+=chars[rd.nextInt(chars.length)]+"";
            graphics.setColor(new Color(rd.nextInt(254),rd.nextInt(254),rd.nextInt(254)));
            graphics.drawString(string,55*i+rd.nextInt(10),27+rd.nextInt(15));
            code+=string;
        }
        //干扰点
        for (int i = 0; i <25*count ; i++) {
            graphics.setFont(new Font("宋体",Font.PLAIN,15));
            String string=".";
            graphics.setColor(new Color(rd.nextInt(255),rd.nextInt(255),rd.nextInt(255)));
            graphics.drawString(string,rd.nextInt(width),rd.nextInt(height));
        }
        //干扰线
        for (int i = 0; i <count+count/2 ; i++) {
            graphics.setFont(new Font("宋体",Font.PLAIN,10));
            graphics.setColor(new Color(rd.nextInt(255),rd.nextInt(255),rd.nextInt(255)));
            graphics.drawLine(rd.nextInt(width),rd.nextInt(height),rd.nextInt(width),rd.nextInt(height));
        }
        //归还笔
        graphics.dispose();
        //写到流里面需要用到ImageIo
        //这里做的测试，在本地测试下是否画的是那回事
        /*try {
            ImageIO.write(image,"jpg",new FileOutputStream("E:/11.jpg"));
        } catch (IOException e) {
            e.printStackTrace();
        }*/
        return image;
    }
}




接下来我们要写servlet代码了，其实就是一个生成验证码的接口



 package Utils;
import javax.imageio.ImageIO;
import javax.servlet.ServletException;
import javax.servlet.ServletOutputStream;
import javax.servlet.annotation.WebServlet;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
import javax.servlet.http.HttpSession;
import java.awt.image.BufferedImage;
import java.io.IOException;

@WebServlet(name = "GetImgServlet",urlPatterns = {"/imgcode"})
public class GetImgServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
    }
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置页面内容为image形式
        response.setContentType("image/jpg");
        //防止乱码
        response.setCharacterEncoding("UTF-8");
        //定义获取验证码的对象
        ImageCode imageCode=new ImageCode();
        //得到图片缓冲区
        BufferedImage img = imageCode.getImage();
        //得到文字验证码
        String code = imageCode.getCode();
        //获得用户session
        HttpSession session = request.getSession();
        //将文字验证码保存到客户端session,方便验证
        session.setAttribute("imgcode",code);
        System.out.println("生成的验证码为："+code);
        //获得sevlet输出流
        ServletOutputStream outputStream = response.getOutputStream();
        //写到客户端
        ImageIO.write(img,"jpg",outputStream);
        //关闭输出流
        if(outputStream!=null){
            outputStream.close();
        }
    }
}

做好验证码api之后我们还要进行前台交互下，看到底有没有作用


这是html文档
   <!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>验证码</title>
    <script src="https://cdn.bootcss.com/jquery/3.3.1/jquery.js"></script>
</head>
<body>
<table border="0" cellpadding="0" cellspacing="0">
    <tr>
        <td>
            <input type="text" name="code">
        </td>
        <td>
            <img src="/imgcode" style="height: 30px;width: 120px">
        </td>
    </tr>
    <tr>
        <td colspan="2">
            <center><button type="button" class="button">验证</button></center>
        </td>
    </tr>
</table>
<script>
    $(document).ready(function () {
        //设置按钮的点击事件
        $(".button").click(function () {
            var code = $("input[name='code']");
            if (code.val() == null || code.val() == "") {
                alert("请输入验证码后再认证");
            } else {
                //有值了，我们就体检到后台验证，通过post
                $.post("/checkcode", code.serialize(), function (data, stauts) {
                    if (stauts = 'success') {
                        if (data == "验证正确")
                            alert("验证正确");
                        else
                            alert("验证码错误");
                    } else {
                        alert("请求错误");
                    }
                })
            }
        })

        //点击图片切换验证码
        $("img").click(function () {
            $("img").attr("src","/imgcode?"+Math.random())
        })
    })
</script>

</body>
</html>

This is the interface to accept a verification code

package Utils;

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 javax.servlet.http.HttpSession;
import java.io.IOException;
import java.io.PrintWriter;

@WebServlet(name = "CheckCodeServlet",urlPatterns ={"/checkcode"})
public class CheckCodeServlet extends HttpServlet {
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //设置页面类型
        response.setContentType("text/html,charset=urf-8");
        response.setCharacterEncoding("utf-8");
        //得到请求参数
        String code = request.getParameter("code");
        //得到session
        HttpSession session = request.getSession();
        //得到生成的验证码
        String imgcode = (String) session.getAttribute("imgcode");
        PrintWriter writer = response.getWriter();
        if (imgcode.equalsIgnoreCase(code)){
            System.out.println(imgcode+"\n"+code);
            writer.print("验证正确");
            //验证之后最好销毁下之前的
            session.setAttribute("imgcode","");
        }else{
            writer.print("验证码错误");
        }
        writer.close();
    }

    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doPost(request,response);
    }
}

Enter the correct code will be prompted to

enter the prompt error

Well, the end of the tutorial, hope to help you, you can get a little change in the use of the actual project