feign客户端扫描与注册FeignClientsRegistrar

最新推荐文章于 2025-10-14 10:39:21 发布

原创最新推荐文章于 2025-10-14 10:39:21 发布 · 2.9k 阅读

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CC 4.0 BY-SA版权

文章标签：

#java #spring #后端

本文解析了 Spring Cloud 中 Feign 客户端的注册机制，详细介绍了如何通过 FeignClientsRegistrar 注册 Feign 客户端，并探讨了其在 Spring 容器中的注册流程。

ImportBeanDefinitionRegistrar：registerBeanDefinitions注册定义的bean对象
ResourceLoaderAware：注册定义的配置
EnvironmentAware：获取springboot运行环境信息

阅读完后思考？
1.feign与ribbon的关系？
2.feign如何实现负载均衡？

一、EnableFeignClients说明

注解EnableFeignClients在使用前需要先导入FeignClientsRegistrar注册客户端启用feign客户端

二、FeignClientsRegistrar说明

FeignClientsRegistrar实现的类
实现ImportBeanDefinitionRegistrar接口中registerBeanDefinitions方法注册路由示例注册feign客户端配置和客户端
注册feign配置到容器

	/**
	 * 获取需要注册的feign客户端列表并执行注册
	 * @param metadata
	 * @param registry
	 */
	public void registerFeignClients(AnnotationMetadata metadata,
			BeanDefinitionRegistry registry) {
		//获取扫描器
		ClassPathScanningCandidateComponentProvider scanner = getScanner();
		scanner.setResourceLoader(this.resourceLoader)
		Set<String> basePackages;
		//获取启用Feign客户端的注解配置参数
		Map<String, Object> attrs = metadata.getAnnotationAttributes(EnableFeignClients.class.getName());
		//获取注解配置过滤器
		AnnotationTypeFilter annotationTypeFilter = new AnnotationTypeFilter(FeignClient.class);
		final Class<?>[] clients = attrs == null ? null
				: (Class<?>[]) attrs.get("clients");
		if (clients == null || clients.length == 0) {
			scanner.addIncludeFilter(annotationTypeFilter);
			basePackages = getBasePackages(metadata);
		}
		else {
			final Set<String> clientClasses = new HashSet<>();
			basePackages = new HashSet<>();
			for (Class<?> clazz : clients) {
				basePackages.add(ClassUtils.getPackageName(clazz));
				clientClasses.add(clazz.getCanonicalName());
			}
			AbstractClassTestingTypeFilter filter = new AbstractClassTestingTypeFilter() {
				@Override
				protected boolean match(ClassMetadata metadata) {
					String cleaned = metadata.getClassName().replaceAll("\\$", ".");
					return clientClasses.contains(cleaned);
				}
			};
			scanner.addIncludeFilter(
					new AllTypeFilter(Arrays.asList(filter, annotationTypeFilter)));
		}

		for (String basePackage : basePackages) {
			//获取指定包下定义的BeanDefinition
			Set<BeanDefinition> candidateComponents = scanner
					.findCandidateComponents(basePackage);
			for (BeanDefinition candidateComponent : candidateComponents) {
				if (candidateComponent instanceof AnnotatedBeanDefinition) {
					// verify annotated class is an interface
					AnnotatedBeanDefinition beanDefinition = (AnnotatedBeanDefinition) candidateComponent;
					AnnotationMetadata annotationMetadata = beanDefinition.getMetadata();
					Assert.isTrue(annotationMetadata.isInterface(),
							"@FeignClient can only be specified on an interface");

					Map<String, Object> attributes = annotationMetadata
							.getAnnotationAttributes(
									FeignClient.class.getCanonicalName());

					String name = getClientName(attributes);
					registerClientConfiguration(registry, name,
							attributes.get("configuration"));

					registerFeignClient(registry, annotationMetadata, attributes);
				}
			}
		}
	}

正式注册客户端到spring容器
private void registerFeignClient(BeanDefinitionRegistry registry,
			AnnotationMetadata annotationMetadata, Map<String, Object> attributes) {
		String className = annotationMetadata.getClassName();
		BeanDefinitionBuilder definition = BeanDefinitionBuilder
				.genericBeanDefinition(FeignClientFactoryBean.class);
		validate(attributes);
		definition.addPropertyValue("url", getUrl(attributes));
		definition.addPropertyValue("path", getPath(attributes));
		String name = getName(attributes);
		definition.addPropertyValue("name", name);
		String contextId = getContextId(attributes);
		definition.addPropertyValue("contextId", contextId);
		definition.addPropertyValue("type", className);
		definition.addPropertyValue("decode404", attributes.get("decode404"));
		definition.addPropertyValue("fallback", attributes.get("fallback"));
		definition.addPropertyValue("fallbackFactory", attributes.get("fallbackFactory"));
		definition.setAutowireMode(AbstractBeanDefinition.AUTOWIRE_BY_TYPE);

		String alias = contextId + "FeignClient";
		AbstractBeanDefinition beanDefinition = definition.getBeanDefinition();
		beanDefinition.setAttribute(FactoryBean.OBJECT_TYPE_ATTRIBUTE, className);

		// has a default, won't be null
		boolean primary = (Boolean) attributes.get("primary");

		beanDefinition.setPrimary(primary);

		String qualifier = getQualifier(attributes);
		if (StringUtils.hasText(qualifier)) {
			alias = qualifier;
		}

		BeanDefinitionHolder holder = new BeanDefinitionHolder(beanDefinition, className,
				new String[] { alias });
		BeanDefinitionReaderUtils.registerBeanDefinition(holder, registry);
	}