Java图片验证码简单实现

一、前言

因为之前做Javaweb项目都是直接copy老师的验证码生成类，没有很仔细的去阅读

几个小时前写一个小项目的时候发现这最好还是自己写，便顺便学了java中的绘图函数

在网上找了一些资料，便开始研究（魔改）了，以下是实现代码

二、代码实现

2.1 前端JSP页面

index.jsp

一个模拟登录的页面，其中有供用户输入的文本框，可以提供简单的校验功能，这里做演示用

<%--
  Created by IntelliJ IDEA.
  User: konley
  Date: 2020/7/9
  Time: 21:14
  To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>

  
    
  
  
    
    

      
      

      

        
        检查
      
    
  

实现点击更换图片使用了原生JavaScript实现，具体代码分析如下

//入口函数
window.onload=function(){
    //获得验证码图片元素，并绑定点击事件
    var codeImg = document.getElementById("checkCode");
    codeImg.onclick=function () {
        //瞎传一个参数，防止浏览器缓存，这里用时间戳，可以做到永不重复
        codeImg.src="CheckCodeServlet?QAQ="+new Date().getTime();
    }
}

也可以用jquery实现，这里略过

2.2 绘制验证码工具类

IdentfiyCode.java

实现绘制验证码的功能，提供了几个构造方法，默认为构造一个160*40，4个字符，干扰线20条的图片

主要方法

public void write(OutputStream sos) ：写入方法

public String getCode()：获得当前验证码，小写形式

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
import javax.imageio.ImageIO;

public class IdentifyCode {
    // 图片的宽度。
    private int width = 160;
    // 图片的高度。
    private int height = 40;
    // 验证码字符个数
    private int codeCount = 4;
    // 验证码干扰线数
    private int lineCount = 20;
    // 验证码
    private String code = null;
    // 验证码图片Buffer
    private BufferedImage buffImg = null;
    Random random = new Random();

    // 生成默认定义的图片
    public IdentifyCode() {
        creatImage();
    }

    // 自定义图片宽和高
    public IdentifyCode(int width, int height) {
        this.width = width;
        this.height = height;
        creatImage();
    }

    // 自定义图片宽、高和字符个数
    public IdentifyCode(int width, int height, int codeCount) {
        this.width = width;
        this.height = height;
        this.codeCount = codeCount;
        creatImage();
    }

    // 自定义宽、高、字符个数和干扰线条数
    public IdentifyCode(int width, int height, int codeCount, int lineCount) {
        this.width = width;
        this.height = height;
        this.codeCount = codeCount;
        this.lineCount = lineCount;
        creatImage();
    }

    // 生成图片
    private void creatImage() {
        int fontWidth = width / codeCount;// 字体的宽度
        int fontHeight = height - 5;// 字体的高度
        int codeY = height - 8;

        // 图像buffer
        buffImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics g = buffImg.getGraphics();
        // Graphics2D g = buffImg.createGraphics();
        // 设置背景色
        g.setColor(getRandColor(200, 250));
        g.fillRect(0, 0, width, height);

        // 设置字体
        // Font font1 = getFont(fontHeight);
        Font font = new Font("Fixedsys", Font.BOLD, fontHeight);
        g.setFont(font);

        // 设置干扰线
        for (int i = 0; i < lineCount; i++) {
            int xs = random.nextInt(width);
            int ys = random.nextInt(height);
            int xe = xs + random.nextInt(width);
            int ye = ys + random.nextInt(height);
            g.setColor(getRandColor(1, 255));
            g.drawLine(xs, ys, xe, ye);
        }

        // 添加噪点
        float yawpRate = 0.01f;// 噪声率
        int area = (int) (yawpRate * width * height);
        for (int i = 0; i < area; i++) {
            int x = random.nextInt(width);
            int y = random.nextInt(height);

            buffImg.setRGB(x, y, random.nextInt(255));
        }

        String str1 = randomStr(codeCount);// 得到随机字符
        this.code = str1;
        for (int i = 0; i < codeCount; i++) {
            String strRand = str1.substring(i, i + 1);
            g.setColor(getRandColor(1, 255));
            // g.drawString(a,x,y);
            // a为要画出来的东西，x和y表示要画的东西最左侧字符的基线位于此图形上下文坐标系的 (x, y) 位置处

            g.drawString(strRand, i * fontWidth + 3, codeY);
        }

    }

    // 得到随机字符
    private String randomStr(int n) {
        String str1 = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
        String str2 = "";
        int len = str1.length() - 1;
        double r;
        for (int i = 0; i < n; i++) {
            r = (Math.random()) * len;
            str2 = str2 + str1.charAt((int) r);
        }
        return str2;
    }

    // 得到随机颜色
    private Color getRandColor(int fc, int bc) {// 给定范围获得随机颜色
        if (fc > 255) {
            fc = 255;
        }
        if (bc > 255) {
            bc = 255;
        }
        int r = fc + random.nextInt(bc - fc);
        int g = fc + random.nextInt(bc - fc);
        int b = fc + random.nextInt(bc - fc);
        return new Color(r, g, b);
    }

    /**
     * 产生随机字体
     */
    private Font getFont(int size) {
        Random random = new Random();
        Font font[] = new Font[5];
        font[0] = new Font("Ravie", Font.PLAIN, size);
        font[1] = new Font("Antique Olive Compact", Font.PLAIN, size);
        font[2] = new Font("Fixedsys", Font.PLAIN, size);
        font[3] = new Font("Wide Latin", Font.PLAIN, size);
        font[4] = new Font("Gill Sans Ultra Bold", Font.PLAIN, size);
        return font[random.nextInt(5)];
    }

    // 扭曲方法
    private void shear(Graphics g, int w1, int h1, Color color) {
        shearX(g, w1, h1, color);
        shearY(g, w1, h1, color);
    }

    private void shearX(Graphics g, int w1, int h1, Color color) {

        int period = random.nextInt(2);

        boolean borderGap = true;
        int frames = 1;
        int phase = random.nextInt(2);

        for (int i = 0; i < h1; i++) {
            double d = (double) (period >> 1)
                    * Math.sin((double) i / (double) period
                    + (6.2831853071795862D * (double) phase)
                    / (double) frames);
            g.copyArea(0, i, w1, 1, (int) d, 0);
            if (borderGap) {
                g.setColor(color);
                g.drawLine((int) d, i, 0, i);
                g.drawLine((int) d + w1, i, w1, i);
            }
        }

    }

    private void shearY(Graphics g, int w1, int h1, Color color) {

        int period = random.nextInt(40) + 10; // 50;

        boolean borderGap = true;
        int frames = 20;
        int phase = 7;
        for (int i = 0; i < w1; i++) {
            double d = (double) (period >> 1)
                    * Math.sin((double) i / (double) period
                    + (6.2831853071795862D * (double) phase)
                    / (double) frames);
            g.copyArea(i, 0, 1, h1, 0, (int) d);
            if (borderGap) {
                g.setColor(color);
                g.drawLine(i, (int) d, i, 0);
                g.drawLine(i, (int) d + h1, i, h1);
            }

        }

    }
    //写入方法
    public void write(OutputStream sos) throws IOException {
        ImageIO.write(buffImg, "png", sos);
        sos.close();
    }

    public BufferedImage getBuffImg() {
        return buffImg;
    }

    //获取取得的验证码，小写形式
    public String getCode() {
        return code.toLowerCase();
    }

}

2.3 请求验证码图片的Servlet

CheckCodeServlet.java

使用IdentfiyCode工具类获取验证码后，写入到jsp中

并将验证码存入session，用于后面的校验

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.io.IOException;

/**
 * @author konley
 * @date 2020-07-09 21:18
 */
@WebServlet("/CheckCodeServlet")
public class CheckCodeServlet extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // 设置响应的类型格式为图片格式
        response.setContentType("image/jpeg");
        // 禁止图像缓存。
        response.setHeader("Pragma", "no-cache");
        response.setHeader("Cache-Control", "no-cache");
        response.setDateHeader("Expires", 0);

        // 自定义宽、高、字数和干扰线的条数
        IdentifyCode code = new IdentifyCode(100, 30, 4, 10);
        // 将验证码code存入session
        HttpSession session = request.getSession();
        session.setAttribute("code", code.getCode());
        // 响应图片
        ServletOutputStream out = response.getOutputStream();
        code.write(out);
        try {
            out.flush();
        } finally {
            out.close();
        }
    }
}

2.4 简单的用户输入校验

将用户输入的验证码与工具类生成的验证码进行比对，这里以比对完毕后在页面显示为例

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;
import java.io.PrintWriter;

/**
 * @author konley
 * @date 2020-07-09 21:44
 */
@WebServlet("/Longin")
public class Longin extends HttpServlet {
    @Override
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        doGet(request,response);
    }

    @Override
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        //获取用户输入的验证码和真实验证码
        String inputCode = request.getParameter("inputCode");
        String code = (String) request.getSession().getAttribute("code");
        PrintWriter pw = response.getWriter();
        //简单检验,记得将用户输入转为小写
        if (inputCode.toLowerCase().equals(code)){
            pw.write("success");
        }else{
            pw.write("false");
        }
    }
}

三、效果截图