@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
@Import({FeignClientsRegistrar.class})
public @interface EnableFeignClients {
    String[] value() default {};

    String[] basePackages() default {};

    Class<?>[] basePackageClasses() default {};

    Class<?>[] defaultConfiguration() default {};

    Class<?>[] clients() default {};
}

@Override
public void registerBeanDefinitions(AnnotationMetadata metadata,
      BeanDefinitionRegistry registry)
    //这个方式是注入一些配置，就是对EnableFeignClients注解属性的解析，比如bean 名称等
    registerDefaultConfiguration(metadata, registry);
    //这个方法是扫描加了@FeignClient注解
    registerFeignClients(metadata, registry);
}

public void registerFeignClients(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
        ClassPathScanningCandidateComponentProvider scanner = this.getScanner();
        scanner.setResourceLoader(this.resourceLoader);
        Map<String, Object> attrs = metadata.getAnnotationAttributes(EnableFeignClients.class.getName());
        AnnotationTypeFilter annotationTypeFilter = new AnnotationTypeFilter(FeignClient.class);
        Class<?>[] clients = attrs == null ? null : (Class[])((Class[])attrs.get("clients"));
        Object basePackages;
        if (clients != null && clients.length != 0) {
            final Set<String> clientClasses = new HashSet();
            basePackages = new HashSet();
            Class[] var9 = clients;
            int var10 = clients.length;

            for(int var11 = 0; var11 < var10; ++var11) {
                Class<?> clazz = var9[var11];
                ((Set)basePackages).add(ClassUtils.getPackageName(clazz));
                clientClasses.add(clazz.getCanonicalName());
            }

            AbstractClassTestingTypeFilter filter = new AbstractClassTestingTypeFilter() {
                protected boolean match(ClassMetadata metadata) {
                    String cleaned = metadata.getClassName().replaceAll("\$", ".");
                    return clientClasses.contains(cleaned);
                }
            };
            scanner.addIncludeFilter(new FeignClientsRegistrar.AllTypeFilter(Arrays.asList(filter, annotationTypeFilter)));
        } else {
            scanner.addIncludeFilter(annotationTypeFilter);
            basePackages = this.getBasePackages(metadata);
        }

        Iterator var17 = ((Set)basePackages).iterator();

        while(var17.hasNext()) {
            String basePackage = (String)var17.next();
            Set<BeanDefinition> candidateComponents = scanner.findCandidateComponents(basePackage);
            Iterator var21 = candidateComponents.iterator();

            while(var21.hasNext()) {
                BeanDefinition candidateComponent = (BeanDefinition)var21.next();
                if (candidateComponent instanceof AnnotatedBeanDefinition) {
                    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 = this.getClientName(attributes);
                    // 每个Feign的客户端的配置类封装成一个FeignClientSpecification的BeanDefinition，注册到spring容器中
                    this.registerClientConfiguration(registry, name, attributes.get("configuration"));
                    // 重新构造了一个BeanDefinition，这个BeanDefinition的指定的class类型是FeignClientFactoryBean，spring在生成bean的时候，判断BeanDefinition中bean的class如果是FactoryBean的实现的话，会调用这个实现类的getObject来获取对象
                    this.registerFeignClient(registry, annotationMetadata, attributes);
                }
            }
        }

    }