前言
基于之前两篇(《spring boot高性能实现二维码扫码登录(上)——单服务器版》和《spring boot高性能实现二维码扫码登录(中)——Redis版》)的基础，我们使用消息队列的订阅与发布来实现二维码扫码登录的效果。
一、实现原理
1.参考微信的二维码登录机制
首先，请求后端拿到二维码。然后通过http长连接请求后端，并获取登录认证信息。这时，当二维码被扫，则记录seesion并跳转至内部页面。
如果没有扫码二维码，则线程会等到30秒(也有的说是20秒)，如果再此期间，二维码被扫，则唤醒线程。如果二维码没有被扫，并且30秒等待结束，则前端页面再次请求服务器。
2.线程等待机制
我使用CountDownLatch来控制线程的等待和唤醒。控制器返回Callable<>对象来达到“非阻塞”的目的。
3.订阅与广播机制
参考：https://spring.io/guides/gs/messaging-redis/
使用redis的消息队列机制，当然使用别的中间件来做消息队列是可以的。这里是为了演示方便才使用redis，时间项目中我很少用redis做消息队列。
使用单例模式存储一个Map<>对象，用于保存登录状态。当在30秒内请求不到被扫的结果，则阻塞线程。当二维码被扫后，通过redis发送广播，当其中后端服务器(可以是多台服务器)接收到广播后，唤醒被请求的那台服务器的线程。
二、代码编写
<?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 http://maven.apache.org/xsd/maven-4.0.0.xsd"> <modelVersion>4.0.0</modelVersion> <groupId>com.demo</groupId> <artifactId>auth</artifactId> <version>0.0.1-SNAPSHOT</version> <packaging>jar</packaging> <name>auth</name> <description>二维码登录</description> <parent> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-parent</artifactId> <version>2.0.0.RELEASE</version> <relativePath /> <!-- lookup parent from repository --> </parent> <properties> <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding> <project.reporting.outputEncoding>UTF-8</project.reporting.outputEncoding> <java.version>1.8</java.version> </properties> <dependencies> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-thymeleaf</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-web</artifactId> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-devtools</artifactId> <scope>runtime</scope> </dependency> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-test</artifactId> <scope>test</scope> </dependency> <!-- zxing --> <dependency> <groupId>com.google.zxing</groupId> <artifactId>core</artifactId> <version>3.3.0</version> </dependency> <dependency> <groupId>com.google.zxing</groupId> <artifactId>javase</artifactId> <version>3.3.0</version> </dependency> <!-- redis --> <dependency> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-starter-data-redis</artifactId> </dependency> <!-- session --> <dependency> <groupId>org.springframework.session</groupId> <artifactId>spring-session-data-redis</artifactId> </dependency> <dependency> <groupId>commons-codec</groupId> <artifactId>commons-codec</artifactId> </dependency> </dependencies> <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> </plugins> </build> </project>
存储登录状态和接收广播的类：Receiver
package com.demo.auth; import java.util.Map; import java.util.concurrent.ConcurrentHashMap; import java.util.concurrent.CountDownLatch; public class Receiver { public static final String TOPIC_NAME = "login"; /** * 存储登录状态 */ private Map<String, CountDownLatch> loginMap = new ConcurrentHashMap<>(); /** * 接收登录广播 * * @param loginId */ public void receiveLogin(String loginId) { if (loginMap.containsKey(loginId)) { CountDownLatch latch = loginMap.get(loginId); if (latch != null) { // 唤醒登录等待线程 latch.countDown(); } } } public CountDownLatch getLoginLatch(String loginId) { CountDownLatch latch = null; if (!loginMap.containsKey(loginId)) { latch = new CountDownLatch(1); loginMap.put(loginId, latch); } else latch = loginMap.get(loginId); return latch; } public void removeLoginLatch(String loginId) { if (loginMap.containsKey(loginId)) { loginMap.remove(loginId); } } }
bean配置类：
package com.demo.auth; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.data.redis.connection.RedisConnectionFactory; import org.springframework.data.redis.core.StringRedisTemplate; import org.springframework.data.redis.listener.PatternTopic; import org.springframework.data.redis.listener.RedisMessageListenerContainer; import org.springframework.data.redis.listener.adapter.MessageListenerAdapter; @Configuration public class BeanConfig { @Bean public StringRedisTemplate template(RedisConnectionFactory connectionFactory) { return new StringRedisTemplate(connectionFactory); } @Bean public RedisMessageListenerContainer container(RedisConnectionFactory connectionFactory, MessageListenerAdapter listenerAdapter) { RedisMessageListenerContainer container = new RedisMessageListenerContainer(); container.setConnectionFactory(connectionFactory); // 订阅登录消息 container.addMessageListener(listenerAdapter, new PatternTopic(Receiver.TOPIC_NAME)); return container; } @Bean public MessageListenerAdapter listenerAdapter(Receiver receiver) { // 方法名 String methodName = "receiveLogin"; return new MessageListenerAdapter(receiver, methodName); } @Bean public Receiver receiver() { return new Receiver(); } }
控制器类：
package com.demo.auth; import java.awt.image.BufferedImage; import java.io.ByteArrayOutputStream; import java.util.HashMap; import java.util.Hashtable; import java.util.Map; import java.util.UUID; import java.util.concurrent.Callable; import java.util.concurrent.TimeUnit; import javax.imageio.ImageIO; import javax.servlet.http.HttpSession; import org.apache.commons.codec.binary.Base64; import org.springframework.beans.factory.annotation.Autowired; import org.springframework.data.redis.core.StringRedisTemplate; import org.springframework.data.redis.core.ValueOperations; import org.springframework.stereotype.Controller; import org.springframework.ui.Model; import org.springframework.web.bind.annotation.GetMapping; import org.springframework.web.bind.annotation.PathVariable; import org.springframework.web.bind.annotation.ResponseBody; import org.springframework.web.bind.annotation.SessionAttribute; import com.google.zxing.BarcodeFormat; import com.google.zxing.EncodeHintType; import com.google.zxing.MultiFormatWriter; import com.google.zxing.common.BitMatrix; import com.google.zxing.qrcode.decoder.ErrorCorrectionLevel; /** * 控制器 * * @author 刘冬博客http://www.cnblogs.com/GoodHelper * */ @Controller public class MainController { private static final String LOGIN_KEY = "key.value.login."; @Autowired private Receiver receiver; @Autowired private StringRedisTemplate redisTemplate; @GetMapping({ "/", "index" }) public String index(Model model, @SessionAttribute(WebSecurityConfig.SESSION_KEY) String user) { model.addAttribute("user", user); return "index"; } @GetMapping("login") public String login() { return "login"; } /** * 获取二维码 * * @return */ @GetMapping("login/getQrCode") public @ResponseBody Map<String, Object> getQrCode() throws Exception { Map<String, Object> result = new HashMap<>(); String loginId = UUID.randomUUID().toString(); result.put("loginId", loginId); // app端登录地址 String loginUrl = "http://localhost:8080/login/setUser/loginId/"; result.put("loginUrl", loginUrl); result.put("image", createQrCode(loginUrl)); ValueOperations<String, String> opsForValue = redisTemplate.opsForValue(); opsForValue.set(LOGIN_KEY + loginId, loginId, 5, TimeUnit.MINUTES); return result; } /** * app二维码登录地址，这里为了测试才传{user},实际项目中user是通过其他方式传值 * * @param loginId * @param user * @return */ @GetMapping("login/setUser/{loginId}/{user}") public @ResponseBody Map<String, Object> setUser(@PathVariable String loginId, @PathVariable String user) { ValueOperations<String, String> opsForValue = redisTemplate.opsForValue(); String value = opsForValue.get(LOGIN_KEY + loginId); if (value != null) { // 保存认证信息 opsForValue.set(LOGIN_KEY + loginId, user, 1, TimeUnit.MINUTES); // 发布登录广播消息 redisTemplate.convertAndSend(Receiver.TOPIC_NAME, loginId); } Map<String, Object> result = new HashMap<>(); result.put("loginId", loginId); result.put("user", user); return result; } /** * 等待二维码扫码结果的长连接 * * @param loginId * @param session * @return */ @GetMapping("login/getResponse/{loginId}") public @ResponseBody Callable<Map<String, Object>> getResponse(@PathVariable String loginId, HttpSession session) { // 非阻塞 Callable<Map<String, Object>> callable = () -> { Map<String, Object> result = new HashMap<>(); result.put("loginId", loginId); try { ValueOperations<String, String> opsForValue = redisTemplate.opsForValue(); String user = opsForValue.get(LOGIN_KEY + loginId); // 长时间不扫码，二维码失效。需重新获二维码 if (user == null) { result.put("success", false); result.put("stats", "refresh"); return result; } // 已登录 if (!user.equals(loginId)) { // 登录成,认证信息写入session session.setAttribute(WebSecurityConfig.SESSION_KEY, user); result.put("success", true); result.put("stats", "ok"); return result; } // 等待二维码被扫 try { // 线程等待30秒 receiver.getLoginLatch(loginId).await(30, TimeUnit.SECONDS); } catch (Exception e) { e.printStackTrace(); } result.put("success", false); result.put("stats", "waiting"); return result; } finally { // 移除登录请求 receiver.removeLoginLatch(loginId); } }; return callable; } /** * 生成base64二维码 * * @param content * @return * @throws Exception */ private String createQrCode(String content) throws Exception { try (ByteArrayOutputStream out = new ByteArrayOutputStream()) { Hashtable<EncodeHintType, Object> hints = new Hashtable<EncodeHintType, Object>(); hints.put(EncodeHintType.ERROR_CORRECTION, ErrorCorrectionLevel.H); hints.put(EncodeHintType.CHARACTER_SET, "utf-8"); hints.put(EncodeHintType.MARGIN, 1); BitMatrix bitMatrix = new MultiFormatWriter().encode(content, BarcodeFormat.QR_CODE, 400, 400, hints); int width = bitMatrix.getWidth(); int height = bitMatrix.getHeight(); BufferedImage image = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB); for (int x = 0; x < width; x++) { for (int y = 0; y < height; y++) { image.setRGB(x, y, bitMatrix.get(x, y) ? 0xFF000000 : 0xFFFFFFFF); } } ImageIO.write(image, "JPG", out); return Base64.encodeBase64String(out.toByteArray()); } } @GetMapping("/logout") public String logout(HttpSession session) { // 移除session session.removeAttribute(WebSecurityConfig.SESSION_KEY); return "redirect:/login"; } }
登录处理类：
package com.demo.auth; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletResponse; import javax.servlet.http.HttpSession; import org.springframework.context.annotation.Bean; import org.springframework.context.annotation.Configuration; import org.springframework.web.servlet.config.annotation.InterceptorRegistration; import org.springframework.web.servlet.config.annotation.InterceptorRegistry; import org.springframework.web.servlet.config.annotation.WebMvcConfigurer; import org.springframework.web.servlet.handler.HandlerInterceptorAdapter; /** * 登录配置 博客出处：http://www.cnblogs.com/GoodHelper/ * */ @Configuration public class WebSecurityConfig implements WebMvcConfigurer { /** * 登录session key */ public final static String SESSION_KEY = "user"; @Bean public SecurityInterceptor getSecurityInterceptor() { return new SecurityInterceptor(); } public void addInterceptors(InterceptorRegistry registry) { InterceptorRegistration addInterceptor = registry.addInterceptor(getSecurityInterceptor()); // 排除配置 addInterceptor.excludePathPatterns("/error"); addInterceptor.excludePathPatterns("/login"); addInterceptor.excludePathPatterns("/login/**"); // 拦截配置 addInterceptor.addPathPatterns("/**"); } private class SecurityInterceptor extends HandlerInterceptorAdapter { @Override public boolean preHandle(HttpServletRequest request, HttpServletResponse response, Object handler) throws Exception { HttpSession session = request.getSession(); if (session.getAttribute(SESSION_KEY) != null) return true; // 跳转登录 String url = "/login"; response.sendRedirect(url); return false; } } }
application.properties：
# session
spring.session.store-type=redis
前端页面index.html和login.html保存和之前一直：
<!DOCTYPE html> <html xmlns:th="http://www.thymeleaf.org"> <head> <meta charset="UTF-8"> <title>二维码登录</title> </head> <body> <h1>二维码登录</h1> <h4> <a target="_blank" href="http://www.cnblogs.com/GoodHelper/">from 刘冬的博客</a> </h4> <h3 th:text="'登录用户：' + ${user}"></h3> <br /> <a href="/logout">注销</a> </body> </html>
<!DOCTYPE html> <html xmlns:th="http://www.thymeleaf.org"> <head> <meta charset="UTF-8"> <title>二维码登录</title> <script src="//cdn.bootcss.com/angular.js/1.5.6/angular.min.js"></script> <script type="text/javascript"> /*<![CDATA[*/ var app = angular.module('app', []); app.controller('MainController', function($rootScope, $scope, $http) { //二维码图片src $scope.src = null; //获取二维码 $scope.getQrCode = function() { $http.get('/login/getQrCode').success(function(data) { if (!data || !data.loginId || !data.image) return; $scope.src = 'data:image/png;base64,' + data.image $scope.getResponse(data.loginId) }); } //获取登录响应 $scope.getResponse = function(loginId) { $http.get('/login/getResponse/' + loginId).success(function(data) { if (!data) { setTimeout($scope.getQrCode(), 1000); return; } //一秒后，重新获取登录二维码 if (!data.success) { if (data.stats == 'waiting') { //一秒后再次调用 setTimeout(function() { $scope.getResponse(loginId); }, 1000); } else { //重新获取二维码 setTimeout(function() { $scope.getQrCode(loginId); }, 1000); } return; } //登录成功，进去首页 location.href = '/' }).error(function(data, status) { //一秒后，重新获取登录二维码 setTimeout(function() { $scope.getQrCode(loginId); }, 1000); }) } $scope.getQrCode(); }); /*]]>*/ </script> </head> <body ng-app="app" ng-controller="MainController"> <h1>扫码登录</h1> <h4> <a target="_blank" href="http://www.cnblogs.com/GoodHelper/">from 刘冬的博客</a> </h4> <img ng-show="src" ng-src="{{src}}" /> </body> </html>
App.java：
package com.demo.auth; import org.springframework.boot.SpringApplication; import org.springframework.boot.autoconfigure.SpringBootApplication; @SpringBootApplication public class App { public static void main(String[] args) { SpringApplication.run(App.class, args); } }
三、运行效果
如下图所示，请求后台，如果没有扫码结果，则等待30秒：
如果30后，二维码依然没有被扫，则返回http状态200的相应。前端则需再次发起请求：
如果长时间不扫(5分钟)，则刷新二维码。
整个流程的运行效果如下图所示：
总结
使用Redis作为消息队列的目的是，发送和接受消息订阅。当然，如果是正式项目您最好使用性能高的消息队列中间件，我这里使用Redis是为了演示方便而已。
那么为什么要使用消息队列的订阅和广播呢？那是因为，如果有多台服务器，其中一台“对等”的服务器内存中里存储了登录的CountDownLatch来阻塞线程，而APP端扫码又访问了其他“对等”的服务器，如果不使用“广播机制”，那么阻塞线程的服务器就不会被唤醒，除非APP的请求刚好访问到被阻塞的那天服务器。
好了，关于扫码登录的博客就写完了。如果我这几篇博客中有不完善的地方或者是没有考虑到的地方，欢迎大家留言，谢谢。
如果你觉得我的博客对你有帮助，可以给我点儿打赏，左侧微信，右侧支付宝。
有可能就是你的一点打赏会让我的博客写的更好:)