spring cloud alibaba中RestTemplate 、Ribbon、Nacos Discover整合源码简析

最新推荐文章于 2025-05-08 04:55:15 发布

雷X峰

最新推荐文章于 2025-05-08 04:55:15 发布

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分类专栏： spring cloud 文章标签： spring cloud alibaba resttemplate ribbon nacos discover 负载均衡

本文链接：https://blog.youkuaiyun.com/mapleleafforest/article/details/111387583

本文通过流程图及源码分析，详细阐述了在Spring Cloud Alibaba环境下，RestTemplate如何结合Ribbon和Nacos Discover实现服务调用的负载均衡。从RestTemplate的请求拦截，到RibbonLoadBalancerClient的执行，再到ZoneAwareLoadBalancer的选择逻辑，深入探讨了每个关键步骤的实现细节。

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1 调用流程图

在spring cloud alibaba中，nacos discover提供了对ribbon的支持，其方式和eureka client对ribbon的支持一样，而ResTemplate客户端负载均衡又是依赖ribbon，下图是看完源码后画的一张简要的流程图：
在这里插入图片描述

2 流程图的源码分析

2.1 调用从RestTemplate到LoadBalancerInterceptor

从RestTemplate:getForObject()一路断点到 doExecute()方法

protected <T> T doExecute(URI url, @Nullable HttpMethod method, @Nullable RequestCallback requestCallback,
			@Nullable ResponseExtractor<T> responseExtractor) throws RestClientException {
   
   

		Assert.notNull(url, "URI is required");
		Assert.notNull(method, "HttpMethod is required");
		ClientHttpResponse response = null;
		try {
   
   
			ClientHttpRequest request = createRequest(url, method);
			if (requestCallback != null) {
   
   
				requestCallback.doWithRequest(request);
			}
			response = request.execute();
			handleResponse(url, method, response);
			return (responseExtractor != null ? responseExtractor.extractData(response) : null);
		}
		catch (IOException ex) {
   
   
		    …………
		}
		finally {
   
   
			if (response != null) {
   
   
				response.close();
			}
		}
	}

在request处端点可以发现request对象里的List<ClientHttpRequestInterceptor> interceptors中已经包含了LoadBalancerInterceptor这拦截器。
在这里插入图片描述
接着从request.execute()一路断点到executeInternal()

@Override
	protected final ClientHttpResponse executeInternal(HttpHeaders headers, byte[] bufferedOutput) throws IOException {
   
   
		InterceptingRequestExecution requestExecution = new InterceptingRequestExecution();
		return requestExecution.execute(this, bufferedOutput);
	}
	private class InterceptingRequestExecution implements ClientHttpRequestExecution {
   
   
		private final Iterator<ClientHttpRequestInterceptor> iterator;
		public InterceptingRequestExecution() {
   
   
			this.iterator = interceptors.iterator();
		}
		@Override
		public ClientHttpResponse execute(HttpRequest request, byte[] body) throws IOException {
   
   
			if (this.iterator.hasNext()) {
   
   
				ClientHttpRequestInterceptor nextInterceptor = this.iterator.next(