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本文主要研究一下spring 5的WebClient对reactor-netty的HttpClient的封装

DefaultWebClientBuilder

spring-webflux-5.0.2.RELEASE-sources.jar!/org/springframework/web/reactive/function/client/DefaultWebClientBuilder.java

@Override    public WebClient build() {        ExchangeFunction exchange = initExchangeFunction();        ExchangeFunction filteredExchange = (this.filters != null ? this.filters.stream()                .reduce(ExchangeFilterFunction::andThen)                .map(filter -> filter.apply(exchange))                .orElse(exchange) : exchange);        return new DefaultWebClient(filteredExchange, initUriBuilderFactory(),                unmodifiableCopy(this.defaultHeaders), unmodifiableCopy(this.defaultCookies),                new DefaultWebClientBuilder(this));    }

这里的build调用了initExchangeFunction方法

private ExchangeFunction initExchangeFunction() {        if (this.exchangeFunction != null) {            return this.exchangeFunction;        }        else if (this.connector != null) {            return ExchangeFunctions.create(this.connector, this.exchangeStrategies);        }        else {            return ExchangeFunctions.create(new ReactorClientHttpConnector(), this.exchangeStrategies);        }    }

这里new了一个ReactorClientHttpConnector

ReactorClientHttpConnector

spring-web-5.0.2.RELEASE-sources.jar!/org/springframework/http/client/reactive/ReactorClientHttpConnector.java

/**     * Create a Reactor Netty {@link ClientHttpConnector}     * with default {@link ClientOptions} and HTTP compression support enabled.     */    public ReactorClientHttpConnector() {        this.httpClient = HttpClient.builder()                .options(options -> options.compression(true))                .build();    }

可以看到这个构造器使用了reactor/ipc/netty/http/client/HttpClient

DefaultWebClient

spring-webflux-5.0.2.RELEASE-sources.jar!/org/springframework/web/reactive/function/client/DefaultWebClient.java

@Override    public RequestHeadersUriSpec
     get() {        return methodInternal(HttpMethod.GET);    }    @Override    public RequestHeadersUriSpec
     head() {        return methodInternal(HttpMethod.HEAD);    }    @Override    public RequestBodyUriSpec post() {        return methodInternal(HttpMethod.POST);    }    @Override    public RequestBodyUriSpec put() {        return methodInternal(HttpMethod.PUT);    }    @Override    public RequestBodyUriSpec patch() {        return methodInternal(HttpMethod.PATCH);    }    @Override    public RequestHeadersUriSpec
     delete() {        return methodInternal(HttpMethod.DELETE);    }    @Override    public RequestHeadersUriSpec
     options() {        return methodInternal(HttpMethod.OPTIONS);    }    @Override    public RequestBodyUriSpec method(HttpMethod httpMethod) {        return methodInternal(httpMethod);    }    @SuppressWarnings("unchecked")    private RequestBodyUriSpec methodInternal(HttpMethod httpMethod) {        return new DefaultRequestBodyUriSpec(httpMethod);    }

DefaultWebClient主要对GET、HEAD、POST、PUT、PATCH、DELETE、OPTIONS方法封装返回RequestHeadersUriSpec或者RequestBodyUriSpec

@Override        public Mono
    
      exchange() {            ClientRequest request = (this.inserter != null ?                    initRequestBuilder().body(this.inserter).build() :                    initRequestBuilder().build());            return exchangeFunction.exchange(request).switchIfEmpty(NO_HTTP_CLIENT_RESPONSE_ERROR);        }
    

最后在exchange方法里头封装了对exchangeFunction的调用，这里的switchIfEmpty返回的是reactor.core.publisher.MonoSwitchIfEmpty<ClientResponse>

spring-webflux-5.0.2.RELEASE-sources.jar!/org/springframework/web/reactive/function/client/ExchangeFunctions.java

public Mono
    
      exchange(ClientRequest request) {            Assert.notNull(request, "'request' must not be null");            return this.connector                    .connect(request.method(), request.url(),                            clientHttpRequest -> request.writeTo(clientHttpRequest, this.strategies))                    .log("org.springframework.web.reactive.function.client", Level.FINE)                    .map(clientHttpResponse -> new DefaultClientResponse(clientHttpResponse,                            this.strategies));        }
    

这里调用了ReactorClientHttpConnector的connect方法

spring-web-5.0.2.RELEASE-sources.jar!/org/springframework/http/client/reactive/ReactorClientHttpConnector.java

public Mono
    
      connect(HttpMethod method, URI uri,            Function
     > requestCallback) {        if (!uri.isAbsolute()) {            return Mono.error(new IllegalArgumentException("URI is not absolute: " + uri));        }        return this.httpClient                .request(adaptHttpMethod(method),                        uri.toString(),                        request -> requestCallback.apply(adaptRequest(method, uri, request)))                .map(this::adaptResponse);    }
    

connect方法最后调用的reactor-netty的HttpClient的request方法。

小结

spring 5的webflux部分主要基于reactor项目来的，WebClient也是基于reactor-netty来实现，主要是封装了一些UriSpec及其他便利方法。

接口见spring-webflux-5.0.2.RELEASE-sources.jar!/org/springframework/web/reactive/function/client/WebClient.java