SpringCloudOpenFeign源码解析

  • Z时代
  • 2024-01-10
  • 分类：综合

编程

0. 入门demo

  • 此代码是 OpenFeign 的示例代码，获取一个Github 仓库的所有贡献者，创建一个issue。 建议由此开始 DEBUG 调试阅读源码

interface GitHub {
  @RequestLine("GET /repos/{owner}/{repo}/contributors")
  List<contributor> contributors(@Param("owner") String owner, @Param("repo") String repo);
  @RequestLine("POST /repos/{owner}/{repo}/issues")
  void createIssue(Issue issue, @Param("owner") String owner, @Param("repo") String repo);
}
public static class Contributor {
  String login;
  int contributions;
}
public static class Issue {
  String title;
  String body;
  List<string> assignees;
  int milestone;
  List<string> labels;
}
public class MyApp {
  public static void main(String... args) {
    GitHub github = Feign.builder()
                         .decoder(new GsonDecoder())
                         .target(GitHub.class, "https://api.github.com");
    // Fetch and print a list of the contributors to this library.
    List<contributor> contributors = github.contributors("OpenFeign", "feign");
    for (Contributor contributor : contributors) {
      System.out.println(contributor.login + " (" + contributor.contributions + ")");
    }
  }
}

Feign.build 注入依赖配置项

    public Feign build() {
      SynchronousMethodHandler.Factory synchronousMethodHandlerFactory =
          new SynchronousMethodHandler.Factory(client, retryer, requestInterceptors, logger,
              logLevel, decode404, closeAfterDecode, propagationPolicy);
      ParseHandlersByName handlersByName =
          new ParseHandlersByName(contract, options, encoder, decoder, queryMapEncoder,
              errorDecoder, synchronousMethodHandlerFactory);
      return new ReflectiveFeign(handlersByName, invocationHandlerFactory, queryMapEncoder);
    }

调用JDK动态代理生成接口代理类

动态代理生成接口对象

public class ReflectiveFeign extends Feign {
	@Override
	public <t> T newInstance(Target<t> target) {
		//使用Contract解析接口类上的方法和注解，转换单独MethodHandler处理
		Map<string, methodhandler> nameToHandler = targetToHandlersByName.apply(target);
		// 使用DK动态代理为接口生成代理对象，实际业务逻辑交给 InvocationHandler 处理，其实就是调用 MethodHandler 
		InvocationHandler handler = factory.create(target, methodToHandler);
		T proxy = (T) Proxy.newProxyInstance(target.type().getClassLoader(), new Class<!--?-->[]{target.type()}, handler);
		return proxy;
	}
}

解析接口方法注解信息

  • 如何解析上文 Demo 中 Github.contributors 方法的注解信息呢。 Feign中提供一个Contract 解析协议，有如下实现。

默认支持解析逻辑

class Default extends Contract.BaseContract {
	protected void processAnnotationOnMethod(MethodMetadata data, Annotation methodAnnotation, Method method) {
		Class<!--? extends Annotation--> annotationType = methodAnnotation.annotationType();
		if (annotationType == RequestLine.class) {
			//@RequestLine	注解处理逻辑
		} else if (annotationType == Body.class) {
			//@Body	注解处理逻辑
		} else if (annotationType == Headers.class) {
			//@Headers	注解处理逻辑
		}
	}
	protected boolean processAnnotationsOnParameter(MethodMetadata data, Annotation[] annotations, int paramIndex) {
		boolean isHttpAnnotation = false;
		for (Annotation annotation : annotations) {
			Class<!--? extends Annotation--> annotationType = annotation.annotationType();
			if (annotationType == Param.class) {
				Param paramAnnotation = (Param) annotation;
				//@Param	注解处理逻辑
			} else if (annotationType == QueryMap.class) {
				//@QueryMap	注解处理逻辑
			} else if (annotationType == HeaderMap.class) {
				//@HeaderMap	注解处理逻辑
			}
		}
		return isHttpAnnotation;
	}
}

原生的常用注解

Annotation

Interface Target

@RequestLine

Method

@Param

Parameter

@Headers

Method, Type

@QueryMap

Parameter

@HeaderMap

Parameter

@Body

Method

Spring MVC 扩展注解

  • SpringMvcContract 为 spring-cloud-open-feign 的扩展支持SpringMVC注解，现 feign 版本也已支持

public class SpringMvcContract  {
	// 处理类上的 @RequestMapping
	@Override
	protected void processAnnotationOnClass(MethodMetadata data, Class<!--?--> clz) {
		if (clz.getInterfaces().length == 0) {
			RequestMapping classAnnotation = findMergedAnnotation(clz,
					RequestMapping.class);
		}
	}
	// 处理 @RequestMapping 注解，当然也支持衍生注解 @GetMapping @PostMapping 等处理
	@Override
	protected void processAnnotationOnMethod(MethodMetadata data,
											 Annotation methodAnnotation, Method method) {
		if (!RequestMapping.class.isInstance(methodAnnotation) &amp;&amp; !methodAnnotation
				.annotationType().isAnnotationPresent(RequestMapping.class)) {
			return;
		}
		RequestMapping methodMapping = findMergedAnnotation(method, RequestMapping.class);
		// 获取请求方法
		RequestMethod[] methods = methodMapping.method();
		// produce处理
		parseProduces(data, method, methodMapping);
		// consumes处理
		parseConsumes(data, method, methodMapping);
		// headers头处理
		parseHeaders(data, method, methodMapping);
		data.indexToExpander(new LinkedHashMap<integer, param.expander>());
	}
	// 处理 请求参数 SpringMVC 原生注解
	@Override
	protected boolean processAnnotationsOnParameter(MethodMetadata data,
													Annotation[] annotations, int paramIndex) {
		Param.Expander expander = this.convertingExpanderFactory
				.getExpander(typeDescriptor);
		if (expander != null) {
			data.indexToExpander().put(paramIndex, expander);
		}
		return isHttpAnnotation;
	}
}

MethodHandler 请求处理逻辑

MethodHandler 路由

如上图， 根据不同的请求方法路由到不同的 MethodHandler 实现

final class SynchronousMethodHandler implements MethodHandler {
	@Override
	public Object invoke(Object[] argv) throws Throwable {
		// 获取请求模板
		RequestTemplate template = buildTemplateFromArgs.create(argv);
		// 参数处理
		Options options = findOptions(argv);
		// 默认的重试器
		Retryer retryer = this.retryer.clone();
		while (true) {
			try {
				// 执行请求拦截器
				Request request = targetRequest(template);
				// 输出请求报文
				if (logLevel != Logger.Level.NONE) {
					logger.logRequest(metadata.configKey(), logLevel, request);
				}
				Response response = client.execute(request, options);
				// 根据返回的状态码 ，做 Decode 处理
				...
				return response;
			} catch (RetryableException e) {
				// 执行重试的相关逻辑
			}
		}
	}
}

根据不同参数构建请求模板

  • 表单提交 、还是直接body 提交

执行请求拦截器生成最终Request

// 获取全部的请求拦截器，一个个执行
  Request targetRequest(RequestTemplate template) {
    for (RequestInterceptor interceptor : requestInterceptors) {
      interceptor.apply(template);
    }
    return target.apply(template);
  }

请求日志处理

  • 日志输出级别，配置

public enum Level {
	/**
	 * 不输出
	 */
	NONE,
	/**
	 * 只记录输出Http 方法、URL、状态码、执行时间
	 */
	BASIC,
	/**
	 * 输出请求头 和 Http 方法、URL、状态码、执行时间
	 */
	HEADERS,
	/**
	 * 输出请求头、报文体 和 Http 方法、URL、状态码、执行时间
	 */
	FULL
}

Client 执行最终的Requst 请求

默认default 处理

  • 通过JDK 的 java.net包 实现，没请求都会创建连接实现。可以配置成 HttpClient 或者 OKHttp 的高性能实现

class Default implements Client {
	private final SSLSocketFactory sslContextFactory;
	private final HostnameVerifier hostnameVerifier;
	@Override
	public Response execute(Request request, Request.Options options) throws IOException {
		HttpURLConnection connection = convertAndSend(request, options);
		return convertResponse(connection, request);
	}
」

Spring Cloud 的负载均衡处理

// Spring Cloud 的Client 实现
public class FeignBlockingLoadBalancerClient {
	@Override
	public Response execute(Request request, Request.Options options) throws IOException {
		// 例如请求： http://pig-auth-server/token/info
		final URI originalUri = URI.create(request.url());
		// 截取到serviceId: pig-auth-server
		String serviceId = originalUri.getHost();
		// 调用 loadBalancer API 获取到可以的服务实例
		ServiceInstance instance = loadBalancerClient.choose(serviceId);
		// 构建真实的请求URL http://172.17.0.110:8763/token/info
		String reconstructedUrl = loadBalancerClient.reconstructURI(instance, originalUri)
				.toString();
		// 创建请求 并执行
		Request newRequest = Request.create(request.httpMethod(), reconstructedUrl,
				request.headers(), request.requestBody());
		return delegate.execute(newRequest, options);
	}
}

返回报文Decoder 处理

  • 默认处理

  class Default implements Encoder {
    @Override
    public void encode(Object object, Type bodyType, RequestTemplate template) {
      if (bodyType == String.class) {
        template.body(object.toString());
      } else if (bodyType == byte[].class) {
        template.body((byte[]) object, null);
      } else if (object != null) {
        throw new EncodeException(
            format("%s is not a type supported by this encoder.", object.getClass()));
      }
    }
  }

  • 若是返回报文报错处理

  public static class Default implements ErrorDecoder {
    private final RetryAfterDecoder retryAfterDecoder = new RetryAfterDecoder();
    @Override
    public Exception decode(String methodKey, Response response) {
      FeignException exception = errorStatus(methodKey, response);
      Date retryAfter = retryAfterDecoder.apply(firstOrNull(response.headers(), RETRY_AFTER));
      if (retryAfter != null) {
        return new RetryableException(
            response.status(),
            exception.getMessage(),
            response.request().httpMethod(),
            exception,
            retryAfter,
            response.request());
      }
      return exception;
    }
    private <t> T firstOrNull(Map<string, collection<t>&gt; map, String key) {
      if (map.containsKey(key) &amp;&amp; !map.get(key).isEmpty()) {
        return map.get(key).iterator().next();
      }
      return null;
    }
  }
}

注入 自定义的 ErrorDecoder 比较常用。

以上内容为 OpenFeign 的请求处理流程，下面为扩展内容 spring-cloud-open-feign 是如何初始化及其运行的呢?

【扩展】 Spring Cloud OpenFeign

EnableFeignClients 解析

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

  • 当我们在 Main 方法，加上 @EnableFeignClients 注解，则开启了 spring-cloud-open-feign的相关功能。

  • Import(FeignClientsRegistrar.class) 导入FeignClientsRegistrar,扫描 @FeignClient 注入到容器

FeignClientsRegistrar

class FeignClientsRegistrar {
	@Override
	public void registerBeanDefinitions(AnnotationMetadata metadata,
										BeanDefinitionRegistry registry) {
		registerFeignClients(metadata, registry);
	}
	public void registerFeignClients(AnnotationMetadata metadata,
									 BeanDefinitionRegistry registry) {
		// 扫描配置注解中配置范围内的 @FeignClient
		for (String basePackage : basePackages) {
			// 注入IOC 容器
			registerClientConfiguration(registry, name,
							attributes.get("configuration"));
		}
	}
	//feignclient &lt;--&gt; bean 构造
	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);
		...
		BeanDefinitionHolder holder = new BeanDefinitionHolder(beanDefinition, className,
				new String[] { alias });
		BeanDefinitionReaderUtils.registerBeanDefinition(holder, registry);
	}
}

默认情况

public class FeignAutoConfiguration {
    // 未引入 feign-hystrix 模块，则还是注入 DefaultTargeter
    @Configuration(proxyBeanMethods = false)
    @ConditionalOnMissingClass("feign.hystrix.HystrixFeign")
    protected static class DefaultFeignTargeterConfiguration {
    	@Bean
    	@ConditionalOnMissingBean
    	public Targeter feignTargeter() {
    		return new DefaultTargeter();
    	}
    }
}

未引入 feign-hystrix 则还是上文的流程就同最初的流程一致 ， 我们在调用 feignclient.method 会触发动态代理,执行 MethodHandler 的逻辑

HystrixFeign

  • 首先，引入了 HystrixFeign，是不是意味逻辑变得更了呢

最初 0. 入门DemoFeign.builder(),就变成了 HystrixFeign.builder()

public final class HystrixFeign {
	public static Builder builder() {
		return new Builder();
	}
	public static final class Builder extends Feign.Builder {
		// 注入 HystrixInvocationHandler 的实现
		Feign build(final FallbackFactory<!--?--> nullableFallbackFactory) {
			super.invocationHandlerFactory(new InvocationHandlerFactory() {
				@Override
				public InvocationHandler create(Target target,
												Map<method, methodhandler> dispatch) {
					return new HystrixInvocationHandler(target, dispatch, setterFactory,
							nullableFallbackFactory);
				}
			});
			super.contract(new HystrixDelegatingContract(contract));
			return super.build();
		}
	}
}

  • 注入 HystrixInvocationHandler 的实现，使用HystrixCommand 包装，最终还是使用methodhandler 去调用最终的接口

final class HystrixInvocationHandler implements InvocationHandler {
	@Override
	public Object invoke(final Object proxy, final Method method, final Object[] args)
			throws Throwable {
		// 使用HystrixCommand 包装
		HystrixCommand<object> hystrixCommand =
				new HystrixCommand<object>(setterMethodMap.get(method)) {
					@Override
					protected Object run() throws Exception {
						try {
							// 调用 methodhandler 处理最终的请求
							return HystrixInvocationHandler.this.dispatch.get(method).invoke(args);
						} catch (Exception e) {
							throw e;
						} catch (Throwable t) {
							throw (Error) t;
						}
					}
				};
		return hystrixCommand.execute();
	}
}

SentinelFeign

  • 先看类注释 like {@link HystrixFeign.Builder} ，"借鉴" HystrixFeign

/**
 * {@link Feign.Builder} like {@link HystrixFeign.Builder}.
 */
public final class SentinelFeign {
}

  • 注入 SentinelInvocationHandler 的实现，使用Sentinel包装，最终还是使用methodhandler 去调用最终的接口

public class SentinelInvocationHandler implements InvocationHandler {
	@Override
	public Object invoke(final Object proxy, final Method method, final Object[] args)
			throws Throwable {
		// 使用sentinel 包装请求
		try {
			ContextUtil.enter(resourceName);
			entry = SphU.entry(resourceName, EntryType.OUT, 1, args);
			result = methodHandler.invoke(args);
		}
		catch (Throwable ex) {
			// fallback 逻辑
		}
		finally {
			ContextUtil.exit();
		}
		return result;
	}
}

总结时序图

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