Operating environment:
IDEA：2021.2.4
Tomcat server: Tomcat 8.5.81
JDK：java1.8.0
Building a Java Web environment will not be explained in detail, because it is very basic!
Let's get to work!
Today we are going to create 2 classes [Generate Captcha class, Servlet class] and a JSP file that displays the QR code
To briefly explain first, this is a small feature [core] in one of my experiments
Here is my project structure directory: (FYI)
Our protagonist today is three of these files:
- The main function of the GenerateCodeServlet under the servlet package: to respond to our browser request and call the Java class ValidateCode to generate a verification code
- The ValidateCode class under the validate package, the main function: to generate our captcha image
- The ValidateCode .jsp under the web package displays our captcha
Start by creating our ValidateCode class
Code Reference:
package com.fly.code.validate;
import jdk.internal.util.xml.impl.Input;
import org.junit.Test;
import javax.imageio.ImageIO;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.*;
/**
* @author: fly
* @Date: 2023-03-24 8:52
* @Description:
* 1. 实现动态生成验证码字符串
* 2. 验证码可使用大小写字母+数字的形式
*/
public class ValidateCode {
public static int randomNumber(String str) {
return (int) Math.floor(Math.random()*str.length());
}
/**
* 动态生成验证码字符串 【数字+字母(大小写)】
* @return 4位随机验证码
*/
public static String generateCode(){
// 从该字符串随机抽取 4 个字符
String libs = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz1234567890";
StringBuilder buffer = new StringBuilder();
for (int i = 0;i < 4;i++) {
char ch = libs.charAt(randomNumber(libs));
buffer.append(ch);
}
return String.valueOf(buffer);
}
/**
* 生成图片
*/
public static BufferedImage createImage(String code,String path,int imageWid,int imageHei,int imageType) {
BufferedImage image = new BufferedImage(imageWid,imageHei,imageType);
Graphics2D graph;
graph = image.createGraphics();
// 设置背景色
graph.setBackground(Color.WHITE);
// 设置背景颜色填充范围
graph.fillRect(0,0,imageWid,imageHei);
// 设置画笔颜色
graph.setColor(Color.BLACK);
// 设置字体大小
graph.setFont(new Font("微软雅黑", Font.PLAIN, 25));
// graph.drawLine(0,16,imageWid,16);
graph.drawString(code,imageWid/5,25);
// 保存图片
try {
ImageIO.write(image,"JPG",new File(path));
} catch (IOException e) {
e.printStackTrace();
}
return image;
}
/**
* 保存图片
*/
public static void save(String savePath,String filepath,HttpServletRequest request) {
InputStream is = null;
OutputStream os = null;
byte[] buffer = new byte[1024];
int len = 0;
try {
is = new FileInputStream(filepath);
os = new FileOutputStream(savePath);
while((len = is.read(buffer)) != -1) {
os.write(buffer,0,len);
}
} catch (IOException e) {
e.printStackTrace();
} finally {
if (is != null) {
try {
is.close();
} catch (IOException e) {
e.printStackTrace();
}
}
if (os != null) {
try {
os.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
} Among them, the method of saving pictures (save) is not used Oh~
Next, create our GenerateCodeServlet class
Code:
package com.fly.code.servlet; /**
* @author: fly
* @Date: 2023-03-24 9:12
* @Description: 返回验证码图片
*/
import com.fly.code.validate.ValidateCode;
import org.apache.tomcat.jni.Time;
import org.junit.Test;
import javax.servlet.*;
import javax.servlet.http.*;
import javax.servlet.annotation.*;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.io.InputStream;
import java.util.Arrays;
import java.util.Properties;
import java.util.UUID;
@WebServlet(name = "GenerateCodeServlet", value = "/generateCodeServlet")
public class GenerateCodeServlet extends HttpServlet {
private static final String BASE_URL = "D:\\学习2\\大三下\\物联网平台应用设计\\实验4";
@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
// 获取随机验证码
String code = ValidateCode.generateCode();
// HttpSession对象存储验证码
HttpSession session = request.getSession();
session.setAttribute("code",code);
// BufferedImage(一个带缓冲区图像类)将生成的验证码图片存到一个图像缓冲区
String uuid = String.valueOf(UUID.randomUUID());
uuid = uuid.replaceAll("-","");
session.setAttribute("uuid",uuid);
String path = "/validate-code/" + uuid + ".jpg";
String realPath = request.getServletContext().getRealPath(path);
// 创建二维码图片，并保存到 /validate-code 目录下
ValidateCode.createImage(code,realPath,100,32,BufferedImage.TYPE_INT_RGB);
try {
// 等待图片生成完毕
Thread.sleep(5000);
} catch (InterruptedException e) {
e.printStackTrace();
}
// 重定向到登录页面
response.sendRedirect("/test/ValidateCode.jsp");
}
}
Finally, create the JSP file
Code:
<%@ page import="java.io.*" %><%--
Created by IntelliJ IDEA.
User: local-feng
Date: 2023/3/24
Time: 10:19
To change this template use File | Settings | File Templates.
--%>
<%@ page contentType="text/html;charset=UTF-8" language="java" %>
<html>
<head>
<title>验证码图片显示</title>
</head>
<body>
<%
String uuid = (String) session.getAttribute("uuid");
String path = "/validate-code/" + uuid + ".jpg";
path = request.getContextPath() + path;
%>
<img src="<%=path%>" title="验证码" alt="验证码">
</body>
</html> Okay, run our Tomcat container!
Tomcat is configured as follows:
Visit our website: http://localhost:8023/test/generateCodeServlet
After waiting 5 seconds for the captcha image to be generated, we successfully see the captcha in the browser
We can also see the captcha image we generated in File Explorer:
Expand your knowledge:
With captcha, what can we do? Of course, the landing page!
Understand this dynamic generation of captcha, you can also make a landing page!
Maybe it's not me who generates the verification code online, because this method is too slow, and I need to wait for the generation time of the verification code image.
For example: like this! This is an experiment in our class, [of course, the interface is not carefully beautified]