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聊聊spring cloud gateway的streaming-media-types属性

本文主要研究下spring cloud gateway的streaming-media-types属性

配置

配置说明

    {
      "sourceType": "org.springframework.cloud.gateway.config.GatewayProperties",
      "name": "spring.cloud.gateway.streaming-media-types",
      "type": "java.util.List<org.springframework.http.MediaType>"
    }
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GatewayProperties

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/config/GatewayProperties.java

@ConfigurationProperties("spring.cloud.gateway")
@Validated
public class GatewayProperties {

	/**
	 * List of Routes
	 */
	@NotNull
	@Valid
	private List<RouteDefinition> routes = new ArrayList<>();

	/**
	 * List of filter definitions that are applied to every route.
	 */
	private List<FilterDefinition> defaultFilters = new ArrayList<>();

	private List<MediaType> streamingMediaTypes = Arrays.asList(MediaType.TEXT_EVENT_STREAM,
			MediaType.APPLICATION_STREAM_JSON);

	public List<RouteDefinition> getRoutes() {
		return routes;
	}

	public void setRoutes(List<RouteDefinition> routes) {
		this.routes = routes;
	}

	public List<FilterDefinition> getDefaultFilters() {
		return defaultFilters;
	}

	public void setDefaultFilters(List<FilterDefinition> defaultFilters) {
		this.defaultFilters = defaultFilters;
	}

	public List<MediaType> getStreamingMediaTypes() {
		return streamingMediaTypes;
	}

	public void setStreamingMediaTypes(List<MediaType> streamingMediaTypes) {
		this.streamingMediaTypes = streamingMediaTypes;
	}

	@Override
	public String toString() {
		return "GatewayProperties{" +
				"routes=" + routes +
				", defaultFilters=" + defaultFilters +
				", streamingMediaTypes=" + streamingMediaTypes +
				'}';
	}
}
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可以看到默认是MediaType.TEXT_EVENT_STREAM(text/event-stream)、MediaType.APPLICATION_STREAM_JSON(application/stream+json)

使用

GatewayAutoConfiguration

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/config/GatewayAutoConfiguration.java

	@Configuration
	@ConditionalOnClass(HttpClient.class)
	protected static class NettyConfiguration {
		@Bean
		@ConditionalOnMissingBean
		public HttpClient httpClient(@Qualifier("nettyClientOptions") Consumer<? super HttpClientOptions.Builder> options) {
			return HttpClient.create(options);
		}

		//......

		@Bean
		public HttpClientProperties httpClientProperties() {
			return new HttpClientProperties();
		}

		@Bean
		public NettyRoutingFilter routingFilter(HttpClient httpClient,
												ObjectProvider<List<HttpHeadersFilter>> headersFilters) {
			return new NettyRoutingFilter(httpClient, headersFilters);
		}

		@Bean
		public NettyWriteResponseFilter nettyWriteResponseFilter(GatewayProperties properties) {
			return new NettyWriteResponseFilter(properties.getStreamingMediaTypes());
		}

		@Bean
		public ReactorNettyWebSocketClient reactorNettyWebSocketClient(@Qualifier("nettyClientOptions") Consumer<? super HttpClientOptions.Builder> options) {
			return new ReactorNettyWebSocketClient(options);
		}
	}
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这里的NettyWriteResponseFilter使用到了properties.getStreamingMediaTypes()

NettyWriteResponseFilter

spring-cloud-gateway-core-2.0.0.RC2-sources.jar!/org/springframework/cloud/gateway/filter/NettyWriteResponseFilter.javac

public class NettyWriteResponseFilter implements GlobalFilter, Ordered {

	private static final Log log = LogFactory.getLog(NettyWriteResponseFilter.class);

	public static final int WRITE_RESPONSE_FILTER_ORDER = -1;

	private final List<MediaType> streamingMediaTypes;

	public NettyWriteResponseFilter(List<MediaType> streamingMediaTypes) {
		this.streamingMediaTypes = streamingMediaTypes;
	}

	@Override
	public int getOrder() {
		return WRITE_RESPONSE_FILTER_ORDER;
	}

	@Override
	public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
		// NOTICE: nothing in "pre" filter stage as CLIENT_RESPONSE_ATTR is not added
		// until the WebHandler is run
		return chain.filter(exchange).then(Mono.defer(() -> {
			HttpClientResponse clientResponse = exchange.getAttribute(CLIENT_RESPONSE_ATTR);

			if (clientResponse == null) {
				return Mono.empty();
			}
			log.trace("NettyWriteResponseFilter start");
			ServerHttpResponse response = exchange.getResponse();

			NettyDataBufferFactory factory = (NettyDataBufferFactory) response.bufferFactory();
			//TODO: what if it's not netty

			final Flux<NettyDataBuffer> body = clientResponse.receive()
					.retain() //TODO: needed?
					.map(factory::wrap);

			MediaType contentType = response.getHeaders().getContentType();
			return (isStreamingMediaType(contentType) ?
					response.writeAndFlushWith(body.map(Flux::just)) : response.writeWith(body));
		}));
	}

	//TODO: use framework if possible
	//TODO: port to WebClientWriteResponseFilter
	private boolean isStreamingMediaType(@Nullable MediaType contentType) {
		return (contentType != null && this.streamingMediaTypes.stream()
						.anyMatch(contentType::isCompatibleWith));
	}

}
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可以看到这里根据isStreamingMediaType方法判断是否是stream类型,如果是则采用writeAndFlushWith方法,不是则采用writeWith方法

ReactiveHttpOutputMessage

spring-web-5.0.6.RELEASE-sources.jar!/org/springframework/http/ReactiveHttpOutputMessage.java

/**
 * A "reactive" HTTP output message that accepts output as a {@link Publisher}.
 *
 * <p>Typically implemented by an HTTP request on the client-side or an
 * HTTP response on the server-side.
 *
 * @author Arjen Poutsma
 * @author Sebastien Deleuze
 * @since 5.0
 */
public interface ReactiveHttpOutputMessage extends HttpMessage {

	/**
	 * Return a {@link DataBufferFactory} that can be used to create the body.
	 * @return a buffer factory
	 * @see #writeWith(Publisher)
	 */
	DataBufferFactory bufferFactory();

	/**
	 * Register an action to apply just before the HttpOutputMessage is committed.
	 * <p><strong>Note:</strong> the supplied action must be properly deferred,
	 * e.g. via {@link Mono#defer} or {@link Mono#fromRunnable}, to ensure it's
	 * executed in the right order, relative to other actions.
	 * @param action the action to apply
	 */
	void beforeCommit(Supplier<? extends Mono<Void>> action);

	/**
	 * Whether the HttpOutputMessage is committed.
	 */
	boolean isCommitted();

	/**
	 * Use the given {@link Publisher} to write the body of the message to the
	 * underlying HTTP layer.
	 * @param body the body content publisher
	 * @return a {@link Mono} that indicates completion or error
	 */

	Mono<Void> writeWith(Publisher<? extends DataBuffer> body);

	/**
	 * Use the given {@link Publisher} of {@code Publishers} to write the body
	 * of the HttpOutputMessage to the underlying HTTP layer, flushing after
	 * each {@code Publisher<DataBuffer>}.
	 * @param body the body content publisher
	 * @return a {@link Mono} that indicates completion or error
	 */
	Mono<Void> writeAndFlushWith(Publisher<? extends Publisher<? extends DataBuffer>> body);

	/**
	 * Indicate that message handling is complete, allowing for any cleanup or
	 * end-of-processing tasks to be performed such as applying header changes
	 * made via {@link #getHeaders()} to the underlying HTTP message (if not
	 * applied already).
	 * <p>This method should be automatically invoked at the end of message
	 * processing so typically applications should not have to invoke it.
	 * If invoked multiple times it should have no side effects.
	 * @return a {@link Mono} that indicates completion or error
	 */
	Mono<Void> setComplete();

}
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从接口的注释可以看到,writeWith与writeAndFlushWith的参数泛型不同,一个是Publisher<? extends DataBuffer>,一个是Publisher<? extends Publisher<? extends DataBuffer>>。而writeAndFlushWith则是在每个Publisher写入之后就flush。

小结

NettyWriteResponseFilter根据spring.cloud.gateway.streaming-media-types配置的类型来判断是writeAndFlushWith还是writeWith,如果是指定类型则选择用writeAndFlushWith写入response。默认该配置指定了MediaType.TEXT_EVENT_STREAM(text/event-stream)、MediaType.APPLICATION_STREAM_JSON(application/stream+json)这两种类型。

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