SpringCloud FeignClient 生成代理过程

 

文章目录

• 1. @EnableFeignClients注解
• 2. 注入类FeignClientsRegistrar.class
• 3 FeignClientFactoryBean类
• 4.番外

1. @EnableFeignClients注解

@Retention(RetentionPolicy.RUNTIME)
@Target({ElementType.TYPE})
@Documented
@Import({FeignClientsRegistrar.class})
public @interface EnableFeignClients

我们使用@EnableFeignClients来开启feign的功能。从源码中看,该注解主要作用是通过@Import注解引入FeignClientsRegistrar类，追踪源码。

2. 注入类FeignClientsRegistrar.class

class FeignClientsRegistrar implements ImportBeanDefinitionRegistrar, ResourceLoaderAware, BeanClassLoaderAware, EnvironmentAware 

该类实现了ResourceLoaderAware,BeanClassLoaderAware,EnvironmentAware接口，在解析@import注解的过程中会将感兴趣的bean注入到该类中。实现了ImportBeanDefinitionRegisterar接口，通过重写registerBeanDefinitions方法来注册默认的feign配置类和注册feignClients对应的FeignClientFactoryBean到容器当中。看一下源码：

public void registerBeanDefinitions(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
        this.registerDefaultConfiguration(metadata, registry); // 注册@EnableFeignClients指定的默认配置类到容器
        this.registerFeignClients(metadata, registry);//注册feignClients对应的feignClientFactoryBean到容器
}

注册feignclients,实际上是其对应的工厂bean
public void registerFeignClients(AnnotationMetadata metadata, BeanDefinitionRegistry registry) {
        ClassPathScanningCandidateComponentProvider scanner = this.getScanner();
        scanner.setResourceLoader(this.resourceLoader);// 注解扫描器
        Map<String, Object> attrs = metadata.getAnnotationAttributes(EnableFeignClients.class.getName());
        AnnotationTypeFilter annotationTypeFilter = new AnnotationTypeFilter(FeignClient.class); // 设置扫描的目标注解
        Class<?>[] clients = attrs == null ? null : (Class[])((Class[])attrs.get("clients"));
        Object basePackages;
        if (clients != null && clients.length != 0) {
            .........

        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);
                    this.registerClientConfiguration(registry, name, attributes.get("configuration"));
                    this.registerFeignClient(registry, annotationMetadata, attributes);
                }
            }
        }

    }

注册方法：registerFeignClient

 private void registerFeignClient(BeanDefinitionRegistry registry, AnnotationMetadata annotationMetadata, Map<String, Object> attributes) 

3 FeignClientFactoryBean类

FeignClientFactoryBean 是一个工厂bean，提供了获取FeignClient代理bean的getObject方法,直接看一下方法源码：

 public Object getObject() throws Exception

4 生成feign代理类的，追踪源码到ReflectiveFeign。

public Object getObject() throws Exception {
        FeignContext context = (FeignContext)this.applicationContext.getBean(FeignContext.class);
        Builder builder = this.feign(context);
        ........
       
            Targeter targeter = (Targeter)this.get(context, Targeter.class);
            return targeter.target(this, builder, context, new HardCodedTarget(this.type, this.name, url));
        }
    }

        public <T> T target(Target<T> target) {
            return this.build().newInstance(target);
        }

 public <T> T newInstance(Target<T> target) {
        Map<String, MethodHandler> nameToHandler = this.targetToHandlersByName.apply(target);
        Map<Method, MethodHandler> methodToHandler = new LinkedHashMap();
        List<DefaultMethodHandler> defaultMethodHandlers = new LinkedList();
        Method[] var5 = target.type().getMethods();
        int var6 = var5.length;

        for(int var7 = 0; var7 < var6; ++var7) {
            Method method = var5[var7];
            if (method.getDeclaringClass() != Object.class) {
                if (Util.isDefault(method)) {
                    DefaultMethodHandler handler = new DefaultMethodHandler(method);
                    defaultMethodHandlers.add(handler);
                    methodToHandler.put(method, handler);
                } else {
                    methodToHandler.put(method, nameToHandler.get(Feign.configKey(target.type(), method)));
                }
            }
        }

        InvocationHandler handler = this.factory.create(target, methodToHandler);
        T proxy = Proxy.newProxyInstance(target.type().getClassLoader(), new Class[]{target.type()}, handler);
        Iterator var12 = defaultMethodHandlers.iterator();

        while(var12.hasNext()) {
            DefaultMethodHandler defaultMethodHandler = (DefaultMethodHandler)var12.next();
            defaultMethodHandler.bindTo(proxy);
        }

        return proxy;
    }