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本文主要研究一下spring 5的WebClient對(duì)reactor-netty的HttpClient的封裝

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));
    }   

這里的build調(diào)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);
        }
    }

這里new了一個(gè)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();
    }

可以看到這個(gè)構(gòu)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主要對(duì)GET、HEAD登淘、POST缸榛、PUT扼脐、PATCH霹粥、DELETE、OPTIONS方法封裝返回RequestHeadersUriSpec或者RequestBodyUriSpec

        @Override
        public Mono<ClientResponse> 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方法里頭封裝了對(duì)exchangeFunction的調(diào)用损同，這里的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<ClientResponse> 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));
        }

這里調(diào)用了ReactorClientHttpConnector的connect方法

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

    public Mono<ClientHttpResponse> connect(HttpMethod method, URI uri,
            Function<? super ClientHttpRequest, Mono<Void>> 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方法最后調(diào)用的reactor-netty的HttpClient的request方法帐偎。

小結(jié)

spring 5的webflux部分主要基于reactor項(xiàng)目來(lái)的，WebClient也是基于reactor-netty來(lái)實(shí)現(xiàn)御雕，主要是封裝了一些UriSpec及其他便利方法矢沿。

接口見(jiàn)spring-webflux-5.0.2.RELEASE-sources.jar!/org/springframework/web/reactive/function/client/WebClient.java