Spring Cloud Gateway 源码剖析之配置初始化

梦里梦外; 2022-11-15 03:50 200阅读 0赞

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## 一、前言 ##

相信大多数公司都会有自己公司的专有网关服务，虽说是自研，但很少会有从零开始开发一个网关服务，基本上是基于市面上比较流行的网关组件像 Zuul、Gateway、Soul 等进行二次封装的。那如果自己公司有相应的网关业务需求的话，这就要对网关产品的底层原理要比较熟悉了，这样做起来也比较顺手。本系列只针对 Gateway 组件进行源码剖析，我在想第一篇如何说会比较好，本来想直接说核心流程的，想了想还是先从配置初始化说起。话不多说，接下来我们就开始 Spring Cloud Gateway 源码剖析之旅吧。

## 二、揭秘配置初始化 ##

那我们就从项目中 maven 依赖的 jar 包开始吧。

<dependency>
        <groupId>org.springframework.cloud</groupId>
        <artifactId>spring-cloud-starter-gateway</artifactId>
    </dependency>

直接跟进去发现有三个依赖，凭借我们的开发经验，盲猜一下 spring-cloud-gateway-core 就是 gateway 的核心依赖。  
![在这里插入图片描述][20210330221816281.png]  
直接找到对应的 maven 依赖包：

![在这里插入图片描述][20210330222150422.png]  
不知道大家有没有什么疑问，找了这个包，然后 gateway 是怎么与 Spring Boot 项目相关联的呢？

相信有一定经验的朋友知道 Spring Boot 启动的时候有个 @SpringBootApplication 注解，而这个注解包含了一个非常重要的子注解 @EnableAutoConfiguration，该注解表示开启自动配置功能，是 Spring Boot 框架最重要的注解，也是实现自动化配置的注解。

Spring Cloud Gateway 也是同样的套路，那我们直接找到 /META-INF/spring.factories 文件，果不其然

![在这里插入图片描述][20210330223153708.png]

> // Auto Configure  
> org.springframework.boot.autoconfigure.EnableAutoConfiguration=  
> // 依赖包的校验配置  
> org.springframework.cloud.gateway.config.GatewayClassPathWarningAutoConfiguration,  
> // 网关的核心配置  
> org.springframework.cloud.gateway.config.GatewayAutoConfiguration,  
> // 负载均衡相关依赖配置信息  
> org.springframework.cloud.gateway.config.GatewayLoadBalancerClientAutoConfiguration,  
> // 度量相关依赖配置信息  
> org.springframework.cloud.gateway.config.GatewayMetricsAutoConfiguration,  
> // 流控的依赖配置信息  
> org.springframework.cloud.gateway.config.GatewayRedisAutoConfiguration,  
> // 注册中心相关的依赖配置  
> org.springframework.cloud.gateway.discovery.GatewayDiscoveryClientAutoConfiguration

分析上面的自动配置之前，我们先来了解下 SpringBoot 常用注解的含义。

> // 执行顺序  
> @AutoConfigureBefore：在指定的配置类初始化前加载  
> @AutoConfigureAfter：在指定的配置类初始化后再加载  
> @AutoConfigureOrder：数越小越先初始化  
> // 条件配置  
> @ConditionalOnClass ： classpath中存在该类时起效  
> @ConditionalOnMissingClass ： classpath中不存在该类时起效  
> @ConditionalOnBean ： DI容器中存在该类型Bean时起效  
> @ConditionalOnMissingBean ： DI容器中不存在该类型Bean时起效  
> @ConditionalOnSingleCandidate ： DI容器中该类型Bean只有一个或@Primary的只有一个时起效  
> @ConditionalOnExpression ： SpEL表达式结果为true时  
> @ConditionalOnProperty ： 参数设置或者值一致时起效  
> @ConditionalOnResource ： 指定的文件存在时起效  
> @ConditionalOnJndi ： 指定的JNDI存在时起效  
> @ConditionalOnJava ： 指定的Java版本存在时起效  
> @ConditionalOnWebApplication ： Web应用环境下起效  
> @ConditionalOnNotWebApplication ： 非Web应用环境下起效

**1、GatewayClassPathWarningAutoConfiguration**

GatewayClassPathWarningAutoConfiguration 用于检查项目是否正确导入 spring-boot-starter-webflux 依赖，而不是错误导入 spring-boot-starter-web 依赖，同时 GatewayClassPathWarningAutoConfiguration 在 EnableAutoConfiguration 配置加载前加载。

@Configuration
    // 执行顺序注解
    // 当前注解标识需要在GatewayAutoConfiguration前加载此配置
    @AutoConfigureBefore({ GatewayAutoConfiguration.class})
    public class GatewayClassPathWarningAutoConfiguration { 
        private static final Log log = LogFactory.getLog(GatewayClassPathWarningAutoConfiguration.class);
        private static final String BORDER = "\n\n**********************************************************\n\n";
    
        public GatewayClassPathWarningAutoConfiguration() { 
        }
    
        @Configuration
        // 条件判断注解
        // classpath中不存在org.springframework.web.reactive.DispatcherHandler时起效，标识项目未导入了spring-boot-starter-webflux包
        @ConditionalOnMissingClass({ "org.springframework.web.reactive.DispatcherHandler"})
        protected static class WebfluxMissingFromClasspathConfiguration { 
            public WebfluxMissingFromClasspathConfiguration() { 
            	// 当前项目未导入了spring-boot-starter-webflux依赖时，打印警告日志
                GatewayClassPathWarningAutoConfiguration.log.warn("\n\n**********************************************************\n\nSpring Webflux is missing from the classpath, which is required for Spring Cloud Gateway at this time. Please add spring-boot-starter-webflux dependency.\n\n**********************************************************\n\n");
            }
        }
    
        @Configuration
        // 条件判断注解
        // classpath中存在org.springframework.web.servlet.DispatcherServlet时起效，标识项目导入了spring-boot-starter-web包
        @ConditionalOnClass(
            name = { "org.springframework.web.servlet.DispatcherServlet"}
        )
        protected static class SpringMvcFoundOnClasspathConfiguration { 
            public SpringMvcFoundOnClasspathConfiguration() { 
                // 当前项目导入了spring-boot-starter-web依赖时，打印警告日志
                GatewayClassPathWarningAutoConfiguration.log.warn("\n\n**********************************************************\n\nSpring MVC found on classpath, which is incompatible with Spring Cloud Gateway at this time. Please remove spring-boot-starter-web dependency.\n\n**********************************************************\n\n");
            }
        }
    }

**2、GatewayAutoConfiguration**

GatewayAutoConfiguration 是 Spring Cloud Gateway 核心配置类，这里只列几个核心的，初始化如下 ：

*  RoutePredicateHandlerMapping：查找匹配到 Route 并进行处理
 *  GatewayProperties：加载网关配置
 *  RouteDefinitionRouteLocator：创建一个根据 RouteDefinition 转换的路由定位器
 *  GatewayWebfluxEndpoint：管理网关的 HTTP API

@Configuration
    // 条件注解
    // 通过 spring.cloud.gateway.enabled 配置网关的开启与关闭
    // matchIfMissing = true => 网关默认开启。
    @ConditionalOnProperty(
        name = { "spring.cloud.gateway.enabled"},
        matchIfMissing = true
    )
    @EnableConfigurationProperties
    @AutoConfigureBefore({ HttpHandlerAutoConfiguration.class, WebFluxAutoConfiguration.class})
    @AutoConfigureAfter({ GatewayLoadBalancerClientAutoConfiguration.class, GatewayClassPathWarningAutoConfiguration.class})
    @ConditionalOnClass({ DispatcherHandler.class})
    public class GatewayAutoConfiguration { 
        public GatewayAutoConfiguration() { 
        }
    
        @Bean
        public StringToZonedDateTimeConverter stringToZonedDateTimeConverter() { 
            return new StringToZonedDateTimeConverter();
        }
    
        @Bean
        public RouteLocatorBuilder routeLocatorBuilder(ConfigurableApplicationContext context) { 
            return new RouteLocatorBuilder(context);
        }
    
        @Bean
        @ConditionalOnMissingBean
        public PropertiesRouteDefinitionLocator propertiesRouteDefinitionLocator(GatewayProperties properties) { 
            return new PropertiesRouteDefinitionLocator(properties);
        }
    
        @Bean
        @ConditionalOnMissingBean({ RouteDefinitionRepository.class})
        public InMemoryRouteDefinitionRepository inMemoryRouteDefinitionRepository() { 
            return new InMemoryRouteDefinitionRepository();
        }
    
        @Bean
        @Primary
        public RouteDefinitionLocator routeDefinitionLocator(List<RouteDefinitionLocator> routeDefinitionLocators) { 
            return new CompositeRouteDefinitionLocator(Flux.fromIterable(routeDefinitionLocators));
        }
    
        @Bean
        public RouteLocator routeDefinitionRouteLocator(GatewayProperties properties, List<GatewayFilterFactory> GatewayFilters, List<RoutePredicateFactory> predicates, RouteDefinitionLocator routeDefinitionLocator, @Qualifier("webFluxConversionService") ConversionService conversionService) { 
            return new RouteDefinitionRouteLocator(routeDefinitionLocator, predicates, GatewayFilters, properties, conversionService);
        }
    
        @Bean
        @Primary
        public RouteLocator cachedCompositeRouteLocator(List<RouteLocator> routeLocators) { 
            return new CachingRouteLocator(new CompositeRouteLocator(Flux.fromIterable(routeLocators)));
        }
    
        @Bean
        public RouteRefreshListener routeRefreshListener(ApplicationEventPublisher publisher) { 
            return new RouteRefreshListener(publisher);
        }
    
        @Bean
        public FilteringWebHandler filteringWebHandler(List<GlobalFilter> globalFilters) { 
            return new FilteringWebHandler(globalFilters);
        }
    
        @Bean
        public GlobalCorsProperties globalCorsProperties() { 
            return new GlobalCorsProperties();
        }
    
        @Bean
        public RoutePredicateHandlerMapping routePredicateHandlerMapping(FilteringWebHandler webHandler, RouteLocator routeLocator, GlobalCorsProperties globalCorsProperties, Environment environment) { 
            return new RoutePredicateHandlerMapping(webHandler, routeLocator, globalCorsProperties, environment);
        }
    
        @Bean
        public GatewayProperties gatewayProperties() { 
            return new GatewayProperties();
        }
        ...
    }

**3、GatewayLoadBalancerClientAutoConfiguration**

GatewayLoadBalancerClientAutoConfiguration 作用是初始化 LoadBalancerClientFilter 路由的负载均衡拦截器

@Configuration
    // 条件判断注解
    // classpath中存在LoadBalancerClient和RibbonAutoConfiguration和DispatcherHandler时此配置起效
    @ConditionalOnClass({ LoadBalancerClient.class, RibbonAutoConfiguration.class, DispatcherHandler.class})
    // 执行顺序注解
    @AutoConfigureAfter({ RibbonAutoConfiguration.class})
    @EnableConfigurationProperties({ LoadBalancerProperties.class})
    public class GatewayLoadBalancerClientAutoConfiguration { 
        public GatewayLoadBalancerClientAutoConfiguration() { 
        }
    
        @Bean
        // 条件判断注解
        // DI容器中存在LoadBalancerClient类型Bean时起效
        @ConditionalOnBean({ LoadBalancerClient.class})
        @ConditionalOnMissingBean({ LoadBalancerClientFilter.class})
        public LoadBalancerClientFilter loadBalancerClientFilter(LoadBalancerClient client, LoadBalancerProperties properties) { 
            return new LoadBalancerClientFilter(client, properties);
        }
    }

**4、GatewayMetricsAutoConfiguration**

GatewayMetricsAutoConfiguration 作用是初始化 GatewayMetricsFilter 路由的度量拦截器

@Configuration
    @ConditionalOnProperty(
        name = { "spring.cloud.gateway.enabled"},
        matchIfMissing = true
    )
    @AutoConfigureBefore({ HttpHandlerAutoConfiguration.class})
    @AutoConfigureAfter({ MetricsAutoConfiguration.class, CompositeMeterRegistryAutoConfiguration.class})
    @ConditionalOnClass({ DispatcherHandler.class, MeterRegistry.class, MetricsAutoConfiguration.class})
    public class GatewayMetricsAutoConfiguration { 
        public GatewayMetricsAutoConfiguration() { 
        }
    
        @Bean
        @ConditionalOnBean({ MeterRegistry.class})
        @ConditionalOnProperty(
            name = { "spring.cloud.gateway.metrics.enabled"},
            matchIfMissing = true
        )
        public GatewayMetricsFilter gatewayMetricFilter(MeterRegistry meterRegistry) { 
            return new GatewayMetricsFilter(meterRegistry);
        }
    }

**5、GatewayRedisAutoConfiguration**

GatewayRedisAutoConfiguration 配置作用是初始化初始化 RedisRateLimiter 限流功能的，RequestRateLimiterGatewayFilterFactory 基于 RedisRateLimiter 实现网关的限流功能。

@Configuration
    @AutoConfigureAfter({ RedisReactiveAutoConfiguration.class})
    @AutoConfigureBefore({ GatewayAutoConfiguration.class})
    @ConditionalOnBean({ ReactiveRedisTemplate.class})
    @ConditionalOnClass({ RedisTemplate.class, DispatcherHandler.class})
    class GatewayRedisAutoConfiguration { 
        GatewayRedisAutoConfiguration() { 
        }
    
        @Bean
        public RedisScript redisRequestRateLimiterScript() { 
            DefaultRedisScript redisScript = new DefaultRedisScript();
            redisScript.setScriptSource(new ResourceScriptSource(new ClassPathResource("META-INF/scripts/request_rate_limiter.lua")));
            redisScript.setResultType(List.class);
            return redisScript;
        }
    
        @Bean
        public ReactiveRedisTemplate<String, String> stringReactiveRedisTemplate(ReactiveRedisConnectionFactory reactiveRedisConnectionFactory) { 
            RedisSerializer<String> serializer = new StringRedisSerializer();
            RedisSerializationContext<String, String> serializationContext = RedisSerializationContext.newSerializationContext().key(serializer).value(serializer).hashKey(serializer).hashValue(serializer).build();
            return new ReactiveRedisTemplate(reactiveRedisConnectionFactory, serializationContext);
        }
    
        @Bean
        @ConditionalOnMissingBean
        public RedisRateLimiter redisRateLimiter(ReactiveRedisTemplate<String, String> redisTemplate, @Qualifier("redisRequestRateLimiterScript") RedisScript<List<Long>> redisScript, Validator validator) { 
            return new RedisRateLimiter(redisTemplate, redisScript, validator);
        }
    }

**6、GatewayDiscoveryClientAutoConfiguration**

GatewayDiscoveryClientAutoConfiguration 的作用是初始化配置路由中的注册发现服务信息

@Configuration
    // 同2
    @ConditionalOnProperty(
        name = { "spring.cloud.gateway.enabled"},
        matchIfMissing = true
    )
    @AutoConfigureBefore({ GatewayAutoConfiguration.class})
    @AutoConfigureAfter({ CompositeDiscoveryClientAutoConfiguration.class})
    @ConditionalOnClass({ DispatcherHandler.class, DiscoveryClient.class})
    @EnableConfigurationProperties
    public class GatewayDiscoveryClientAutoConfiguration { 
        public GatewayDiscoveryClientAutoConfiguration() { 
        }
    
        @Bean
        // 当classpath中存在DiscoveryClient起效
        @ConditionalOnBean({ DiscoveryClient.class})
        // 通过spring.cloud.gateway.discovery.locator.enabled配置注册中心查找的开启与关闭
        @ConditionalOnProperty(
            name = { "spring.cloud.gateway.discovery.locator.enabled"}
        )
        public DiscoveryClientRouteDefinitionLocator discoveryClientRouteDefinitionLocator(DiscoveryClient discoveryClient, DiscoveryLocatorProperties properties) { 
            return new DiscoveryClientRouteDefinitionLocator(discoveryClient, properties);
        }
    
        @Bean
        public DiscoveryLocatorProperties discoveryLocatorProperties() { 
            DiscoveryLocatorProperties properties = new DiscoveryLocatorProperties();
            properties.setPredicates(initPredicates());
            properties.setFilters(initFilters());
            return properties;
        }
    
        public static List<PredicateDefinition> initPredicates() { 
            ArrayList<PredicateDefinition> definitions = new ArrayList();
            PredicateDefinition predicate = new PredicateDefinition();
            predicate.setName(NameUtils.normalizeRoutePredicateName(PathRoutePredicateFactory.class));
            predicate.addArg("pattern", "'/'+serviceId+'/**'");
            definitions.add(predicate);
            return definitions;
        }
    
        public static List<FilterDefinition> initFilters() { 
            ArrayList<FilterDefinition> definitions = new ArrayList();
            FilterDefinition filter = new FilterDefinition();
            filter.setName(NameUtils.normalizeFilterFactoryName(RewritePathGatewayFilterFactory.class));
            String regex = "'/' + serviceId + '/(?<remaining>.*)'";
            String replacement = "'/${remaining}'";
            filter.addArg("regexp", regex);
            filter.addArg("replacement", replacement);
            definitions.add(filter);
            return definitions;
        }
    }

## 三、总结 ##

通过自动加载初始化上述六个配置实例，Spring Cloud Gateway 就完成自身的加载和初始化工作。跟着老周下来应该还算清晰吧，下一篇我们来说一下 Route 数据模型，敬请期待~

--------------------

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![在这里插入图片描述][20210305020119946.jpg_pic_center]  
喜欢的话，一键三连走一波。

[20210330221816281.png]: /images/20221022/2e4923376fd14d1cbc8abba246062f61.png
[20210330222150422.png]: /images/20221022/4464922b51ab4727ac93a9de2a5076a2.png
[20210330223153708.png]: /images/20221022/760abf1d612b4e35bf453f31c939525a.png
[20210305020119946.jpg_pic_center]: https://img-blog.csdnimg.cn/20210305020119946.jpg#pic_center