谈不上核心分析

gateway 网关，本质是实现一层反向代理，client提交 获取request,提交给upstream 把upstream 返回的response 返回给client

查看spring-cloud-gateway的反向代理的实现位置

spring-cloud-gateway 提供两种方式的代理，传统的bio，spirng-mvc/serverlet/jetty, 最新的nio,spring webflux/netty

以最简单的get请求为例

对bio包spring-cloud-gateway-mvc

核心类

public class ProxyExchange<T> {
  ...
  private RestTemplate rest;
  public ResponseEntity<T> get() {
		RequestEntity<?> requestEntity = headers((BodyBuilder) RequestEntity.get(uri)).build();
		return exchange(requestEntity);
	}

	private ResponseEntity<T> exchange(RequestEntity<?> requestEntity) {
		Type type = this.responseType;
		if (type instanceof TypeVariable || type instanceof WildcardType) {
			type = Object.class;
		}
		return rest.exchange(requestEntity, ParameterizedTypeReference.forType(responseType));
	}	
}

关键是rest

package org.springframework.web.client;
public class RestTemplate extends InterceptingHttpAccessor implements RestOperations {

对nio 结构类似

包spring-cloud-gateway-webflux

public class ProxyExchange<T> {
	private WebClient rest;
	public Mono<ResponseEntity<T>> get() {
		RequestEntity<?> requestEntity = headers((BodyBuilder) RequestEntity.get(uri)).build();
		return exchange(requestEntity);
	}
  private Mono<ResponseEntity<T>> exchange(RequestEntity<?> requestEntity) {
		Type type = this.responseType;
		RequestBodySpec builder = rest.method(requestEntity.getMethod()).uri(requestEntity.getUrl())
				.headers(headers -> addHeaders(headers, requestEntity.getHeaders()));
		Mono<ClientResponse> result;
		if (requestEntity.getBody() instanceof Publisher) {
			@SuppressWarnings("unchecked")
			Publisher<Object> publisher = (Publisher<Object>) requestEntity.getBody();
			result = builder.body(publisher, Object.class).exchange();
		}
		else if (requestEntity.getBody() != null) {
			result = builder.body(BodyInserters.fromValue(requestEntity.getBody())).exchange();
		}
		else {
			if (hasBody) {
				result = builder.headers(headers -> addHeaders(headers, exchange.getRequest().getHeaders()))
						.body(exchange.getRequest().getBody(), DataBuffer.class).exchange();
			}
			else {
				result = builder.headers(headers -> addHeaders(headers, exchange.getRequest().getHeaders())).exchange();
			}
		}
		return result.flatMap(response -> response.toEntity(ParameterizedTypeReference.forType(type)));
	}
}

rest

package org.springframework.web.reactive.function.client;
public interface WebClient {}

class DefaultWebClient implements WebClient {
...
}