seata 1.2版本集成Feign和ribbon组件源码深入分析（三）

我会带着你远行 2022-12-26 13:28 273阅读 0赞

如果微服务采用feign或ribbon组件做服务调用，seata框架有和feign、ribbon集成的功能，这是微服务的常用组合；

一、下面分析一下feign相关源码：

1、spi入口：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70][]

SeataFeignClientAutoConfiguration 点击进入，找到和fegin相关的核心代码：

@Configuration
    	protected static class FeignBeanPostProcessorConfiguration {
    
    		@Bean
    		SeataBeanPostProcessor seataBeanPostProcessor(
    				SeataFeignObjectWrapper seataFeignObjectWrapper) {
    			return new SeataBeanPostProcessor(seataFeignObjectWrapper);
    		}
    
    		@Bean
    		SeataContextBeanPostProcessor seataContextBeanPostProcessor(
    				BeanFactory beanFactory) {
    			return new SeataContextBeanPostProcessor(beanFactory);
    		}
    
    		@Bean
    		SeataFeignObjectWrapper seataFeignObjectWrapper(BeanFactory beanFactory) {
    			return new SeataFeignObjectWrapper(beanFactory);//重点代码
    		}
    	}

2、SeataFeignObjectWrapper 点击进入，找到核心代码：

SeataFeignObjectWrapper(BeanFactory beanFactory) {
    		this.beanFactory = beanFactory;
    	}
    
    	Object wrap(Object bean) {
    		if (bean instanceof Client && !(bean instanceof SeataFeignClient)) {
    			if (bean instanceof LoadBalancerFeignClient) {
    				LoadBalancerFeignClient client = ((LoadBalancerFeignClient) bean);
    				return new SeataLoadBalancerFeignClient(client.getDelegate(), factory(),
    						clientFactory(), this.beanFactory);
    			}
    //通过feign调用RM 客户端，核心入口
    			return new SeataFeignClient(this.beanFactory, (Client) bean);
    		}
    		return bean;
    	}

3、SeataFeignClient 进入，找到核心代码，此类  public class SeataFeignClient implements Client  实现Client类接口的 execute 方法，

@Override
    	public Response execute(Request request, Request.Options options) throws IOException {
    
    		Request modifiedRequest = getModifyRequest(request);//继续进入
    		return this.delegate.execute(modifiedRequest, options);
    	}
    
    //此方法通过feign调用RM服务，同时把全局事务id封装到header里，传到下游。
    	private Request getModifyRequest(Request request) {
    
    		String xid = RootContext.getXID();
    
    		if (StringUtils.isEmpty(xid)) {
    			return request;
    		}
    
    		Map<String, Collection<String>> headers = new HashMap<>(MAP_SIZE);
    		headers.putAll(request.headers());
    
    		List<String> fescarXid = new ArrayList<>();
    		fescarXid.add(xid);
    		headers.put(RootContext.KEY_XID, fescarXid);//xid 封装到header里
    
            //调用RM对象
    		return Request.create(request.method(), request.url(), headers, request.body(),
    				request.charset());
    	}

继续：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 1][]

继续：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 2][]

到这里就明白了全局事务id是怎么通过feign组件传播的了

二、seata集成ribbon组件源码入口：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L25hbmRhbzE1OA_size_16_color_FFFFFF_t_70 3][]

1、点击进入：SeataRestTemplateAutoConfiguration

@Configuration
    public class SeataRestTemplateAutoConfiguration {
    
        //初始化拦截器类
    	@Bean
    	public SeataRestTemplateInterceptor seataRestTemplateInterceptor() {
    		return new SeataRestTemplateInterceptor();
    	}
    
        //依赖注入
    	@Autowired(required = false)
    	private Collection<RestTemplate> restTemplates;
    
        //依赖注入
    	@Autowired
    	private SeataRestTemplateInterceptor seataRestTemplateInterceptor;
    
        //初始化接口
    	@PostConstruct
    	public void init() {
    		if (this.restTemplates != null) {
    			for (RestTemplate restTemplate : restTemplates) {
    				List<ClientHttpRequestInterceptor> interceptors = new ArrayList<ClientHttpRequestInterceptor>(
    						restTemplate.getInterceptors());
    				interceptors.add(this.seataRestTemplateInterceptor);//核心代码，点击进入
    				restTemplate.setInterceptors(interceptors);
    			}
    		}
    	}
    
    }

2、点击  SeataRestTemplateInterceptor 进入

public class SeataRestTemplateInterceptor implements ClientHttpRequestInterceptor {
    	@Override
    	public ClientHttpResponse intercept(HttpRequest httpRequest, byte[] bytes,
    			ClientHttpRequestExecution clientHttpRequestExecution) throws IOException {
    		HttpRequestWrapper requestWrapper = new HttpRequestWrapper(httpRequest);
    
    		String xid = RootContext.getXID();
    
    		if (!StringUtils.isEmpty(xid)) {
                //这里同样把全局事务id放到 header里
    			requestWrapper.getHeaders().add(RootContext.KEY_XID, xid);
    		}
    		return clientHttpRequestExecution.execute(requestWrapper, bytes);//继续调用，进入
    	}
    }

3、进入

@Override
    		public ClientHttpResponse execute(HttpRequest request, byte[] body) throws IOException {
    			if (this.iterator.hasNext()) {
    				ClientHttpRequestInterceptor nextInterceptor = this.iterator.next();
    				return nextInterceptor.intercept(request, body, this);
    			}
    			else {
    				HttpMethod method = request.getMethod();
    				Assert.state(method != null, "No standard HTTP method");
    				ClientHttpRequest delegate = requestFactory.createRequest(request.getURI(), method);
    				request.getHeaders().forEach((key, value) -> delegate.getHeaders().addAll(key, value));
    				if (body.length > 0) {
    					if (delegate instanceof StreamingHttpOutputMessage) {
    						StreamingHttpOutputMessage streamingOutputMessage = (StreamingHttpOutputMessage) delegate;
    						streamingOutputMessage.setBody(outputStream -> StreamUtils.copy(body, outputStream));
    					}
    					else {
    						StreamUtils.copy(body, delegate.getBody());
    					}
    				}
    				return delegate.execute();
    			}
    		}

4、到这里一目了然，知道了全局事务id是怎么传播的了。

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