spring cloud gateway系列教程3—Global Filters

spring cloud gateway系列教程目錄

  1. spring cloud gateway系列教程1—Route Predicate
  2. spring cloud gateway系列教程2——GatewayFilter_上篇
  3. spring cloud gateway系列教程2——GatewayFilter_下篇
  4. spring cloud gateway系列教程3—Global Filters
  5. spring cloud gateway系列教程4—其他配置

Global Filters

GlobalFilter接口方法和GatewayFilter是一樣的，GlobalFilter特別之處在于它的作用是全局的。

1. Combined Global Filter and GatewayFilter Ordering

當(dāng)請(qǐng)求到來時(shí)，Filtering Web Handler處理器會(huì)添加所有GlobalFilter實(shí)例和匹配的GatewayFilter實(shí)例到過濾器鏈中，通過對(duì)filterbean配置注解@Order，則過濾器鏈會(huì)對(duì)這些過濾器實(shí)例bean進(jìn)行排序。

Spring Cloud Gateway將過濾器的邏輯按請(qǐng)求執(zhí)行點(diǎn)分為”pre"和"post"的一前一后處理，如果是高優(yōu)先級(jí)的過濾器，則在"pre"邏輯中最先執(zhí)行，在"post"邏輯中最后執(zhí)行。

ExampleConfiguration.java.

@Bean
@Order(-1)
public GlobalFilter a() {
    return (exchange, chain) -> {
        log.info("first pre filter");
        return chain.filter(exchange).then(Mono.fromRunnable(() -> {
            log.info("third post filter");
        }));
    };
}

@Bean
@Order(0)
public GlobalFilter b() {
    return (exchange, chain) -> {
        log.info("second pre filter");
        return chain.filter(exchange).then(Mono.fromRunnable(() -> {
            log.info("second post filter");
        }));
    };
}

@Bean
@Order(1)
public GlobalFilter c() {
    return (exchange, chain) -> {
        log.info("third pre filter");
        return chain.filter(exchange).then(Mono.fromRunnable(() -> {
            log.info("first post filter");
        }));
    };
}

上面例子陸續(xù)會(huì)打印的是：

first pre filter
second pre filter
third pre filter
first post filter
second post filter
third post filter

2. Forward Routing Filter

ForwardRoutingFilter會(huì)查看exchange的屬性ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR的URI內(nèi)容，如果url的scheme是forward，比如：forward://localendpoint，則它會(huì)使用Spirng的DispatcherHandler來處理這個(gè)請(qǐng)求。

源碼實(shí)現(xiàn)：

@Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        URI requestUrl = exchange.getRequiredAttribute(GATEWAY_REQUEST_URL_ATTR);

        String scheme = requestUrl.getScheme();
        if (isAlreadyRouted(exchange) || !"forward".equals(scheme)) {
            return chain.filter(exchange);
        }
        setAlreadyRouted(exchange);

        //TODO: translate url?

        if (log.isTraceEnabled()) {
            log.trace("Forwarding to URI: "+requestUrl);
        }

        return this.dispatcherHandler.handle(exchange);
    }

3. LoadBalancerClient Filter

LoadBalancerClientFilter會(huì)查看exchange的屬性ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR的URI內(nèi)容，如果url的scheme是lb，比如：lb://myservice，或者是ServerWebExchangeUtils.GATEWAY_SCHEME_PREFIX_ATTR屬性的內(nèi)容是lb，則它會(huì)使用Spring Cloud的LoadBalancerClient來將host轉(zhuǎn)化為實(shí)際的host和port，并以此替換屬性ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR的內(nèi)容，原來的URL則會(huì)被添加到ServerWebExchangeUtils.GATEWAY_ORIGINAL_REQUEST_URL_ATTR屬性的列表中。

源碼實(shí)現(xiàn)：

@Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        URI url = exchange.getAttribute(GATEWAY_REQUEST_URL_ATTR);
        String schemePrefix = exchange.getAttribute(GATEWAY_SCHEME_PREFIX_ATTR);
        if (url == null || (!"lb".equals(url.getScheme()) && !"lb".equals(schemePrefix))) {
            return chain.filter(exchange);
        }
        //preserve the original url
        addOriginalRequestUrl(exchange, url);

        log.trace("LoadBalancerClientFilter url before: " + url);

        final ServiceInstance instance = loadBalancer.choose(url.getHost());

        if (instance == null) {
            throw new NotFoundException("Unable to find instance for " + url.getHost());
        }

        URI uri = exchange.getRequest().getURI();

        // if the `lb:<scheme>` mechanism was used, use `<scheme>` as the default,
        // if the loadbalancer doesn't provide one.
        String overrideScheme = null;
        if (schemePrefix != null) {
            overrideScheme = url.getScheme();
        }

        URI requestUrl = loadBalancer.reconstructURI(new DelegatingServiceInstance(instance, overrideScheme), uri);

        log.trace("LoadBalancerClientFilter url chosen: " + requestUrl);
        exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, requestUrl);
        return chain.filter(exchange);
    }

application.yml.

spring:
  cloud:
    gateway:
      routes:
      - id: myRoute
        uri: lb://service
        predicates:
        - Path=/service/**

默認(rèn)情況下，如果LoadBalancer找不到服務(wù)實(shí)例，則會(huì)返回HTTP狀態(tài)碼503，你也可以通過修改spring.cloud.gateway.loadbalancer.use404=true配置修改為返回狀態(tài)碼404。

4. Netty Routing Filter

如果ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR屬性中的url的scheme是http或https，則Netty Routing Filter才會(huì)執(zhí)行，并使用Netty作為http請(qǐng)求客戶端對(duì)下游進(jìn)行代理請(qǐng)求。請(qǐng)求的響應(yīng)會(huì)放在exchange的ServerWebExchangeUtils.CLIENT_RESPONSE_ATTR屬性中，以便后面的filter做進(jìn)一步的處理。

5. Netty Write Response Filter

如果NettyWriteResponseFilter發(fā)現(xiàn)exchange的ServerWebExchangeUtils.CLIENT_RESPONSE_ATTR屬性中存在Netty的HttpClientResponse類型實(shí)例，在所有過濾器都執(zhí)行完畢后，它會(huì)將響應(yīng)寫回到gateway客戶端的響應(yīng)中。

源碼實(shí)現(xiàn):

@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));
    }

6. RouteToRequestUrl Filter

如果exchange的ServerWebExchangeUtils.GATEWAY_ROUTE_ATTR屬性存放了Route對(duì)象，則RouteToRequestUrlFilter會(huì)根據(jù)基于請(qǐng)求的URI創(chuàng)建新的URI，新的URI會(huì)更新到ServerWebExchangeUtils.GATEWAY_REQUEST_URL_ATTR屬性中。

如果URI有scheme前綴，比如：lb:ws://serviceid，lbscheme截取出來放到ServerWebExchangeUtils.GATEWAY_SCHEME_PREFIX_ATTR屬性中，方便后面的filter使用。

源碼實(shí)現(xiàn):

@Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        Route route = exchange.getAttribute(GATEWAY_ROUTE_ATTR);
        if (route == null) {
            return chain.filter(exchange);
        }
        log.trace("RouteToRequestUrlFilter start");
        URI uri = exchange.getRequest().getURI();
        boolean encoded = containsEncodedParts(uri);
        URI routeUri = route.getUri();

        if (hasAnotherScheme(routeUri)) {
            // this is a special url, save scheme to special attribute
            // replace routeUri with schemeSpecificPart
            exchange.getAttributes().put(GATEWAY_SCHEME_PREFIX_ATTR, routeUri.getScheme());
            routeUri = URI.create(routeUri.getSchemeSpecificPart());
        }

        URI requestUrl = UriComponentsBuilder.fromUri(uri)
                .uri(routeUri)
                .build(encoded)
                .toUri();
        exchange.getAttributes().put(GATEWAY_REQUEST_URL_ATTR, requestUrl);
        return chain.filter(exchange);
    }

    /* for testing */ static boolean hasAnotherScheme(URI uri) {
        return schemePattern.matcher(uri.getSchemeSpecificPart()).matches() && uri.getHost() == null
                && uri.getRawPath() == null;
    }

7. Websocket Routing Filter

如果請(qǐng)求URL的scheme是ws或wss的話，那么Websocket Routing Filter就會(huì)使用Spring Web Socket底層來處理對(duì)下游的請(qǐng)求轉(zhuǎn)發(fā)。

如果Websocket也使用了負(fù)載均衡，則需要這樣配置：lb:ws://serviceid.

源碼實(shí)現(xiàn)：

@Override
    public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
        changeSchemeIfIsWebSocketUpgrade(exchange);

        URI requestUrl = exchange.getRequiredAttribute(GATEWAY_REQUEST_URL_ATTR);
        String scheme = requestUrl.getScheme();

        if (isAlreadyRouted(exchange) || (!"ws".equals(scheme) && !"wss".equals(scheme))) {
            return chain.filter(exchange);
        }
        setAlreadyRouted(exchange);


        HttpHeaders headers = exchange.getRequest().getHeaders();
        HttpHeaders filtered = filterRequest(getHeadersFilters(),
                exchange);

        List<String> protocols = headers.get(SEC_WEBSOCKET_PROTOCOL);
        if (protocols != null) {
            protocols = headers.get(SEC_WEBSOCKET_PROTOCOL).stream()
                    .flatMap(header -> Arrays.stream(commaDelimitedListToStringArray(header)))
                    .map(String::trim)
                    .collect(Collectors.toList());
        }

        return this.webSocketService.handleRequest(exchange,
                new ProxyWebSocketHandler(requestUrl, this.webSocketClient,
                        filtered, protocols));
    }

8. Making An Exchange As Routed

上面一些像ForwardRoutingFilter、Websocket Routing Filter的源碼中，都可以清楚看到gateway通過設(shè)置gatewayAlreadyRouted標(biāo)識(shí)這個(gè)請(qǐng)求是否已經(jīng)路由轉(zhuǎn)發(fā)出去了，無需其他filter重復(fù)路由，這樣就可以避免重復(fù)錯(cuò)誤的路由操作，保證了路由的實(shí)現(xiàn)靈活性。

ServerWebExchangeUtils.isAlreadyRouted檢查是否已被路由，ServerWebExchangeUtils.setAlreadyRouted標(biāo)記已被路由狀態(tài)。

這一章介紹了Spring Cloud Gateway官方的Global Filters使用場景，下一章講gateway其他配置的使用。

如果想查看其他spring cloud gateway的案例和使用，可以點(diǎn)擊查看

?著作權(quán)歸作者所有,轉(zhuǎn)載或內(nèi)容合作請(qǐng)聯(lián)系作者
【社區(qū)內(nèi)容提示】社區(qū)部分內(nèi)容疑似由AI輔助生成，瀏覽時(shí)請(qǐng)結(jié)合常識(shí)與多方信息審慎甄別。
平臺(tái)聲明：文章內(nèi)容（如有圖片或視頻亦包括在內(nèi)）由作者上傳并發(fā)布，文章內(nèi)容僅代表作者本人觀點(diǎn)，簡書系信息發(fā)布平臺(tái)，僅提供信息存儲(chǔ)服務(wù)。

相關(guān)閱讀更多精彩內(nèi)容

友情鏈接更多精彩內(nèi)容