使用后臺返回驗證碼圖片，驗證碼存到session中后端實現校驗，前端只展示驗證碼圖片。

本篇用SpringBoot Thymeleaf實現驗證碼生成。

創建springboot項目 引入依賴

完整pom.xml

<?xml version='1.0' encoding='UTF-8'?><project xmlns='http://maven.apache.org/POM/4.0.0' xmlns:xsi='http://www.w3.org/2001/XMLSchema-instance' xsi:schemaLocation='http://maven.apache.org/POM/4.0.0 https://maven.apache.org/xsd/maven-4.0.0.xsd'> <modelVersion>4.0.0</modelVersion> <parent><groupId>org.springframework.boot</groupId><artifactId>spring-boot-starter-parent</artifactId><version>2.2.6.RELEASE</version><relativePath/> <!-- lookup parent from repository --> </parent> <groupId>com.example</groupId> <artifactId>web</artifactId> <version>0.0.1-SNAPSHOT</version> <name>web</name> <description>Demo project for Spring Boot</description> <properties><java.version>1.8</java.version> </properties> <dependencies><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId></dependency><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> <exclusions><exclusion> <groupId>org.junit.vintage</groupId> <artifactId>junit-vintage-engine</artifactId></exclusion> </exclusions></dependency><!-- ThymeLeaf 依賴 --><dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-thymeleaf</artifactId></dependency> </dependencies> <build><plugins> <plugin><groupId>org.springframework.boot</groupId><artifactId>spring-boot-maven-plugin</artifactId> </plugin></plugins> </build></project>

application.yml配置 Thymeleaf

#Thymeleaf配置spring: mvc: static-path-pattern: /** thymeleaf: mode: HTML encoding: UTF-8 #關閉緩存 cache: false

創建CaptchaController.java 類

package com.example.web.controller;import com.example.web.util.VerifyCode;import org.springframework.web.bind.annotation.RequestMapping;import org.springframework.web.bind.annotation.RestController;import javax.imageio.ImageIO;import javax.servlet.http.HttpServletRequest;import javax.servlet.http.HttpServletResponse;import java.awt.image.BufferedImage;import java.io.IOException;import java.io.OutputStream;@RestControllerpublic class CaptchaController { /* 獲取驗證碼圖片*/ @RequestMapping('/getVerifyCode') public void getVerificationCode(HttpServletResponse response, HttpServletRequest request) {try { int width = 200; int height = 69; BufferedImage verifyImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);//生成對應寬高的初始圖片 String randomText = VerifyCode.drawRandomText(width, height, verifyImg);//單獨的一個類方法，出于代碼復用考慮，進行了封裝。功能是生成驗證碼字符并加上噪點，干擾線，返回值為驗證碼字符 request.getSession().setAttribute('verifyCode', randomText); response.setContentType('image/png');//必須設置響應內容類型為圖片，否則前臺不識別 OutputStream os = response.getOutputStream(); //獲取文件輸出流 ImageIO.write(verifyImg, 'png', os);//輸出圖片流 os.flush(); os.close();//關閉流} catch (IOException e) { e.printStackTrace();} }}

創建VerifyCode.java 工具類

package com.example.web.util;import java.awt.*;import java.awt.image.BufferedImage;import java.util.Random;public class VerifyCode { public static String drawRandomText(int width, int height, BufferedImage verifyImg) {Graphics2D graphics = (Graphics2D) verifyImg.getGraphics();graphics.setColor(Color.WHITE);//設置畫筆顏色-驗證碼背景色graphics.fillRect(0, 0, width, height);//填充背景graphics.setFont(new Font('微軟雅黑', Font.BOLD, 40));//數字和字母的組合String baseNumLetter = '123456789abcdefghijklmnopqrstuvwxyzABCDEFGHJKLMNPQRSTUVWXYZ';StringBuilder builder = new StringBuilder();int x = 10; //旋轉原點的 x 坐標String ch;Random random = new Random();for (int i = 0; i < 4; i++) { graphics.setColor(getRandomColor()); //設置字體旋轉角度 int degree = random.nextInt() % 30; //角度小于30度 int dot = random.nextInt(baseNumLetter.length()); ch = baseNumLetter.charAt(dot) + ''; builder.append(ch); //正向旋轉 graphics.rotate(degree * Math.PI / 180, x, 45); graphics.drawString(ch, x, 45); //反向旋轉 graphics.rotate(-degree * Math.PI / 180, x, 45); x += 48;}//畫干擾線for (int i = 0; i < 6; i++) { // 設置隨機顏色 graphics.setColor(getRandomColor()); // 隨機畫線 graphics.drawLine(random.nextInt(width), random.nextInt(height), random.nextInt(width), random.nextInt(height));}//添加噪點for (int i = 0; i < 30; i++) { int x1 = random.nextInt(width); int y1 = random.nextInt(height); graphics.setColor(getRandomColor()); graphics.fillRect(x1, y1, 2, 2);}return builder.toString(); } /** * 隨機取色 */ private static Color getRandomColor() {Random ran = new Random();return new Color(ran.nextInt(256),ran.nextInt(256), ran.nextInt(256)); }}

創建UserController.java 類

package com.example.web.controller;import org.springframework.stereotype.Controller;import org.springframework.web.bind.annotation.RequestMapping;@Controllerpublic class UserController { @RequestMapping('/login') public String login() {return 'login'; }}

resources/templates目錄下創建login.html

<!DOCTYPE html><html lang='en' xmlns:th='http://www.thymeleaf.org'><head> <meta charset='UTF-8'> <title>Show User</title></head><body><a href='javascript:void(0);' rel='external nofollow'> <img th:src='http://m.b3g6.com/bcjs/@{getVerifyCode}' onclick='changeCode()' /></a></body><!-- 引入JQuery --><script src='http://m.b3g6.com/static/js/jquery.min.js' th:src='http://m.b3g6.com/bcjs/@{/js/jquery.min.js}'></script><script> function changeCode() {const src = 'http://m.b3g6.com/getVerifyCode?' + new Date().getTime(); //加時間戳，防止瀏覽器利用緩存$(’.verifyCode’).attr('src', src); }</script></html>

啟動項目訪問http://localhost:8080/login

點擊圖片可以更換驗證碼，至于后面的后臺驗證就不講了。參考文章后臺java 實現驗證碼生成

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