spring-boot - Spring WebFlux : Only one connection receive subscriber allowed-6ren

spring-boot - Spring WebFlux : Only one connection receive subscriber allowed

转载作者：行者123 更新时间：2023-12-02 11:50:26

我正在用Spring 5 Webflux和Kotlin编写一个简单的应用程序。我正在尝试通过以下方式实现PUT端点:

PUT("/confs/{id}", {
    val id = it.pathVariable("id")
    ServerResponse.ok().body(service.save(it.bodyToMono(Item::class.java)), Item::class.java)
})

保存的诀窍是，我尝试从项目中读取城市名称，解析地理坐标，将其覆盖在原始项目中，然后使用Spring Data Mongo Reactive repo保存到Mongo。

fun save(item: Mono<Item>): Mono<Item> {
    val geo = item.flatMap {
            val city = it.location?.city ?: "Somewhere"
            geoService.resolveGeoFromCity(city)
    }

    val zipped = item.zipWith(geo)
        .map {
            it.t1.location?.geo = it.t2
            it.t1
        }

    return repo.saveAll(zipped)
        .toMono()
}

解析地理坐标的代码在这里:

@Service
class GeoService() {

    val client = WebClient.create("https://maps.googleapis.com/maps/api/geocode/")

    fun resolveGeoFromCity(city: String): Mono<Geo> {
        return client.get()
                .uri("json?address=$city&key=$API_KEY&language=en")
                .exchange()
                .flatMap { it.bodyToMono(String::class.java) }
                .map { parse(it) }
    }

    private fun parse(response: String): Geo {
        val locationMap = JsonPath.read<Map<String, Double>>(response, "$.results[0].geometry.location")
        return Geo(locationMap["lat"] ?: 0.0, locationMap["lng"] ?: 0.0)
    }

}

问题是，如果发出PUT请求，我将遵循stacktrace。我尝试用 val geo = Mono.just(Geo(0.0, 0.0)) stub Mono(不使用WebClient)，然后工作正常。

如何在不牺牲功能的情况下进行修复？)

    2018-01-01 01:41:00.595 ERROR 15120 --- [ctor-http-nio-4] .a.w.r.e.DefaultErrorWebExceptionHandler : Failed to handle request [PUT http://localhost:8097/confs/5a49675c910d123b1057207a]

    java.lang.IllegalStateException: Only one connection receive subscriber allowed.
        at reactor.ipc.netty.channel.FluxReceive.startReceiver(FluxReceive.java:276) ~[reactor-netty-0.7.2.RELEASE.jar:0.7.2.RELEASE]
        at reactor.ipc.netty.channel.FluxReceive.subscribe(FluxReceive.java:124) ~[reactor-netty-0.7.2.RELEASE.jar:0.7.2.RELEASE]
        at reactor.core.publisher.FluxMap.subscribe(FluxMap.java:62) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:252) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.ipc.netty.ByteBufFlux.subscribe(ByteBufFlux.java:242) ~[reactor-netty-0.7.2.RELEASE.jar:0.7.2.RELEASE]
        at reactor.core.publisher.FluxPeek.subscribe(FluxPeek.java:83) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:252) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.ipc.netty.ByteBufFlux.subscribe(ByteBufFlux.java:242) ~[reactor-netty-0.7.2.RELEASE.jar:0.7.2.RELEASE]
        at reactor.core.publisher.FluxMap.subscribe(FluxMap.java:62) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:252) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.FluxFlatMap.subscribe(FluxFlatMap.java:97) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:252) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.FluxDoFinallyFuseable.subscribe(FluxDoFinallyFuseable.java:48) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:252) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.FluxMapFuseable.subscribe(FluxMapFuseable.java:63) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.FluxOnAssembly.subscribe(FluxOnAssembly.java:252) ~
[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoPeekTerminal.subscribe(MonoPeekTerminal.java:61) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:76) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoPeekFuseable.subscribe(MonoPeekFuseable.java:74) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:76) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:76) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:76) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:76) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:76) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:76) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:76) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.Mono.subscribe(Mono.java:3008) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.drain(MonoIgnoreThen.java:167) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:56) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:76) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:71) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoPeekTerminal.subscribe(MonoPeekTerminal.java:61) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.core.publisher.MonoOnAssembly.subscribe(MonoOnAssembly.java:76) ~[reactor-core-3.1.2.RELEASE.jar:3.1.2.RELEASE]
        at reactor.ipc.netty.channel.ChannelOperations.applyHandler(ChannelOperations.java:383) ~[reactor-netty-0.7.2.RELEASE.jar:0.7.2.RELEASE]
        at reactor.ipc.netty.http.server.HttpServerOperations.onHandlerStart(HttpServerOperations.java:359) ~[reactor-netty-0.7.2.RELEASE.jar:0.7.2.RELEASE]
        at io.netty.util.concurrent.AbstractEventExecutor.safeExecute$$$capture(AbstractEventExecutor.java:163) ~[netty-common-4.1.17.Final.jar:4.1.17.Final]
        at io.netty.util.concurrent.AbstractEventExecutor.safeExecute(AbstractEventExecutor.java) ~[netty-common-4.1.17.Final.jar:4.1.17.Final]
        at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:403) ~[netty-common-4.1.17.Final.jar:4.1.17.Final]
        at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:463) ~[netty-transport-4.1.17.Final.jar:4.1.17.Final]
        at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858) ~[netty-common-4.1.17.Final.jar:4.1.17.Final]
        at java.lang.Thread.run(Thread.java:745) ~[na:1.8.0_112]
        Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
    Assembly trace from producer [reactor.core.publisher.FluxMap] :
        reactor.core.publisher.Flux.map(Flux.java:4855)
        reactor.ipc.netty.ByteBufFlux.fromInbound(ByteBufFlux.java:68)
        reactor.ipc.netty.NettyInbound.receive(NettyInbound.java:90)
        org.springframework.http.server.reactive.ReactorServerHttpRequest.getBody(ReactorServerHttpRequest.java:148)
        org.springframework.http.codec.DecoderHttpMessageReader.readMono(DecoderHttpMessageReader.java:93)
        org.springframework.http.codec.DecoderHttpMessageReader.readMono(DecoderHttpMessageReader.java:123)
        org.springframework.web.reactive.function.BodyExtractors.lambda$null$0(BodyExtractors.java:101)
        java.util.Optional.map(Optional.java:215)
        org.springframework.web.reactive.function.BodyExtractors.readWithMessageReaders(BodyExtractors.java:256)
        org.springframework.web.reactive.function.BodyExtractors.lambda$toMono$2(BodyExtractors.java:96)
        org.springframework.web.reactive.function.server.DefaultServerRequest.body(DefaultServerRequest.java:126)
        org.springframework.web.reactive.function.server.DefaultServerRequest.body(DefaultServerRequest.java:120)
        org.springframework.web.reactive.function.server.DefaultServerRequest.bodyToMono(DefaultServerRequest.java:145)
        com.example.confs.web.ConferenceRouter$routes$1$2.invoke(ConferenceRouter.kt:31)
        com.example.confs.web.ConferenceRouter$routes$1$2.invoke(ConferenceRouter.kt:16)
        org.springframework.web.reactive.function.server.RouterFunctionDsl$PUT$1.handle(RouterFunctionDsl.kt:200)
        org.springframework.web.reactive.function.server.support.HandlerFunctionAdapter.handle(HandlerFunctionAdapter.java:61)
        org.springframework.web.reactive.DispatcherHandler.invokeHandler(DispatcherHandler.java:168)
        org.springframework.web.reactive.DispatcherHandler.lambda$handle$1(DispatcherHandler.java:160)
        reactor.core.publisher.MonoFlatMap$FlatMapMain.onNext(MonoFlatMap.java:118)
        reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:67)
        reactor.core.publisher.MonoNext$NextSubscriber.onNext(MonoNext.java:76)
        reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.innerNext(FluxConcatMap.java:271)
        reactor.core.publisher.FluxConcatMap$ConcatMapInner.onNext(FluxConcatMap.java:803)
        reactor.core.publisher.FluxMapFuseable$MapFuseableSubscriber.onNext(FluxMapFuseable.java:115)
        reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:67)
        reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:67)
        reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:67)
        reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onNext(FluxSwitchIfEmpty.java:67)
        reactor.core.publisher.Operators$ScalarSubscription.request(Operators.java:1649)
        reactor.core.publisher.Operators$MultiSubscriptionSubscriber.set(Operators.java:1463)
        reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onSubscribe(Operators.java:1337)
        reactor.core.publisher.MonoJust.subscribe(MonoJust.java:54)
        reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
        reactor.core.publisher.Mono.subscribe(Mono.java:3008)
        reactor.core.publisher.FluxSwitchIfEmpty$SwitchIfEmptySubscriber.onComplete(FluxSwitchIfEmpty.java:75)
        reactor.core.publisher.Operators.complete(Operators.java:125)
        reactor.core.publisher.MonoEmpty.subscribe(MonoEmpty.java:45)
        reactor.core.publisher.MonoSwitchIfEmpty.subscribe(MonoSwitchIfEmpty.java:44)
        reactor.core.publisher.MonoSwitchIfEmpty.subscribe(MonoSwitchIfEmpty.java:44)
        reactor.core.publisher.MonoSwitchIfEmpty.subscribe(MonoSwitchIfEmpty.java:44)
        reactor.core.publisher.MonoSwitchIfEmpty.subscribe(MonoSwitchIfEmpty.java:44)
        reactor.core.publisher.MonoMapFuseable.subscribe(MonoMapFuseable.java:59)
        reactor.core.publisher.Mono.subscribe(Mono.java:3008)
        reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.drain(FluxConcatMap.java:418)
        reactor.core.publisher.FluxConcatMap$ConcatMapImmediate.onSubscribe(FluxConcatMap.java:210)
        reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:128)
        reactor.core.publisher.FluxIterable.subscribe(FluxIterable.java:61)
        reactor.core.publisher.FluxConcatMap.subscribe(FluxConcatMap.java:121)
        reactor.core.publisher.MonoNext.subscribe(MonoNext.java:40)
        reactor.core.publisher.MonoSwitchIfEmpty.subscribe(MonoSwitchIfEmpty.java:44)
        reactor.core.publisher.MonoFlatMap.subscribe(MonoFlatMap.java:60)
        reactor.core.publisher.MonoFlatMap.subscribe(MonoFlatMap.java:60)
        reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
        reactor.core.publisher.MonoPeekTerminal.subscribe(MonoPeekTerminal.java:61)
        reactor.core.publisher.MonoPeekFuseable.subscribe(MonoPeekFuseable.java:74)
        reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
        reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
        reactor.core.publisher.MonoDefer.subscribe(MonoDefer.java:52)
        reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44)
        reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44)
        reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44)
        reactor.core.publisher.Mono.subscribe(Mono.java:3008)
        reactor.core.publisher.MonoIgnoreThen$ThenIgnoreMain.drain(MonoIgnoreThen.java:167)
        reactor.core.publisher.MonoIgnoreThen.subscribe(MonoIgnoreThen.java:56)
        reactor.core.publisher.MonoOnErrorResume.subscribe(MonoOnErrorResume.java:44)
        reactor.core.publisher.MonoPeekTerminal.subscribe(MonoPeekTerminal.java:61)
        reactor.ipc.netty.channel.ChannelOperations.applyHandler(ChannelOperations.java:383)
        reactor.ipc.netty.http.server.HttpServerOperations.onHandlerStart(HttpServerOperations.java:359)
        io.netty.util.concurrent.AbstractEventExecutor.safeExecute$$$capture(AbstractEventExecutor.java:163)
        io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:403)
        io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:463)
        io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:858)
    Error has been observed by the following operator(s):
        |_  Flux.map(ByteBufFlux.java:68)
        |_  Flux.doOnNext(ByteBufFlux.java:230)
        |_  Flux.map(ReactorServerHttpRequest.java:148)
        |_  Flux.flatMap(AbstractJackson2Decoder.java:95)
        |_  Flux.doFinally(AbstractJackson2Decoder.java:95)
        |_  Flux.map(AbstractJackson2Decoder.java:117)
        |_  Flux.singleOrEmpty(AbstractJackson2Decoder.java:87)
        |_  Operators.error(FluxReceive.java:276)
        |_  Mono.onErrorMap(DefaultServerRequest.java:146)
        |_  Mono.map(ConferenceService.kt:27)
        |_  Mono.map(ConferenceService.kt:32)
        |_  Mono.zipWith(ConferenceService.kt:47)
        |_  Mono.map(ConferenceService.kt:48)
        |_  Flux.flatMap(SimpleReactiveMongoRepository.java:318)
        |_  MonoExtensionsKt.toMono(ConferenceService.kt:55)
        |_  Mono.map(ConferenceService.kt:56)
        |_  Flux.map(AbstractJackson2Encoder.java:99)
        |_  Mono.flatMap(DispatcherHandler.java:177)
        |_  Mono.onErrorResume(DispatcherHandler.java:177)
        |_  Mono.flatMap(DispatcherHandler.java:161)
        |_  Mono.defer(DefaultWebFilterChain.java:71)
        |_  Mono.doOnSuccess(MetricsWebFilter.java:59)
        |_  Mono.doOnError(MetricsWebFilter.java:60)
        |_  Mono.compose(MetricsWebFilter.java:54)
        |_  Mono.defer(DefaultWebFilterChain.java:71)
        |_  Mono.defer(DefaultWebFilterChain.java:71)

最佳答案

WebClient.exchange()结果流是单播的

实际上，这里的问题是WebClient每个连接只允许一个订户。如果您尝试两次订阅相同的交换的连接-您将获得java.lang.IllegalStateException: Only one connection receive subscriber allowed.
尽管我看不到您尝试在哪里重用同一连接两次的事实，但我相信您可以通过使用下一个运算符组合来解决该问题:

class GeoService() {
   val client = WebClient.create("https://maps.googleapis.com/maps/api/geocode/")

   fun resolveGeoFromCity(city: String): Mono<Geo> {
       return client.get()
            .uri("json?address=$city&key=$API_KEY&language=en")
            .exchange()
            .flatMap { it.bodyToMono(String::class.java) }
            .map { parse(it) }
            .share();
   }
   ...
}

在该示例中，只要将订阅至少一个 Subscriber，流就会配置为多播(共享)原始源。
如果您需要所有订阅者都收到相同的日期，则可以将 .share替换为 .cache运算符。

此外，还有一种替代上述技术的方法。您可以用处理器替换提到的运算符，并获得相同的共享可能性:

class GeoService() {

   val client = WebClient.create("https://maps.googleapis.com/maps/api/geocode/")

   fun resolveGeoFromCity(city: String): Mono<Geo> {
       return client.get()
            .uri("json?address=$city&key=$API_KEY&language=en")
            .exchange()
            .flatMap { it.bodyToMono(String::class.java) }
            .map { parse(it) }
            .subscribeWith(DirectProcessor.create());
   }
   ...
}

在这种情况下，您恰好在调用 subscribeWith之后订阅和运行源数据的消耗，因此，在这种情况下，可能会丢失部分数据，依此类推。

为什么使用 Mono.just(..)一切正常？

首先 .just是一个冷运算符，它允许尽可能多的订户在任何时间点接收相同的数据。这就是为什么当您尝试两次从连接中使用相同的数据块时，没有得到任何异常的原因。

关于spring-boot - Spring WebFlux : Only one connection receive subscriber allowed，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/48046238/

文章推荐： java - 如何在 Spark Streaming 中抛出异常

文章推荐： java - eclipse 米洛 : How to define Complex Datatypes?

swift - 为什么 subscribe(subject) 返回 AnyCancellable 但 subscribe(subscriber) Void？
我正在使用 Swift Joint，但不明白两者之间的区别 func subscribe(_ subscriber: S) where S : Subscriber, Self.Failure ==
java - 为什么 Flowable.subscribe(Subscriber) 不返回 Disposable？
大多数 Flowable.subscribe() 重载返回一个 Disposable ，它可以清理流。我习惯于这样做: Disposable d = Flowable.just() .map(
angular - .subscribe(x=> ...) 和 .subscribe(next(...)) 的区别？
我正在尝试测试主题 symbol$ 的输出存在于我的组件上。具体来说，当组件属性 symbol 时，主题符号 $ 应该发出(这是正确的词吗？)已经改变。但是，我找不到测试输出到 symbol$ 的
kotlin - Rx Java，subscribe({}) 与 subscribe { } 有什么区别？
Observable.just(10,20,30,40,50) .subscribe { Consumer{ Log.d(TAG, "Where
angular - RxJS subscribe inside subscribe with actions on error
我在 subscribe 中有带有 subscribe 的代码: this.http.post('/update1', newData).subscribe( (response) => {
meteor - 比较 Meteor.subscribe() 或 this.subscribe() [Meteor + Blaze]
我有两个页面/模板，仪表板(还包含一些用户特定数据)。用户。我正在使用带有 Blaze 模板的 Meteor 1.5。登陆页面是仪表板。我在两个模板中都使用集合 Users 的通用订阅。场景
Angular 2 : Nested subscribe with second subscribe inside the loop
我刚接触 Angular2 一周! 基本上有 2 个 API 调用。第一个 API 调用为我提供了一个 json 对象数组 (queryResults)。 (第一次订阅) 在 View 中显示该数组
Angular 2 无法读取未定义类型错误 : Cannot read property 'subscribe' of undefined 的属性 'subscribe'
我已经在 stackoverflow 上尝试了很多关于修复此错误的提议，但现在我只需要问一下，因为我已经花了很多时间，现在一无所获。我有这个简单的服务: constructor(private ht
java - Spring 集成: Exception Handling on Publish/Subscribe Channels with Ordered Subscribers
给定一个配置有任务执行器的发布-订阅 channel ，如果抛出异常，是否可以中断其有序订阅者的调用？例如，在此示例中，“已工作”消息仍然由序列中的第二个服务激活器发送。我希望这种事不要发生。
java - 无法解析方法 'subscribe(anonymous org.reactivestreams.Subscriber)
我正在尝试使用 Intent to PDF 应用程序下载和发送 pdf 以显示此处显示的文件 answer of JDenais这是下载 pdf 并通过 Intent 传递它的代码。 public c
angular - 使用带有 Angular 的 rxjs .subscribe 防止厄运金字塔 - 压平 .subscribes 的数量
我目前正在调查 RxJS's .merge但是我也会在这里问这个问题，因为我发现这里的解释有时非常精彩。好的，我有一个根据用户输入打开模态窗口的表单，我订阅模态关闭事件并传回一些我将在调用/订阅服务
angular - 类型 'subscribe' 中的属性 'ObservableMedia' 不可分配给基本类型 'Subscribable' 中的同一属性
我刚刚对我的 Angular 6 应用程序进行了 ng 升级，现在我得到: ERROR in node_modules/@angular/flex-layout/core/typings/observ
publish-subscribe - 处理事件驱动架构中的多事件依赖
如果您有一个事件驱动的架构并且订阅事件的服务在继续创建链中的下一个事件之前必须等待多个事件(相同类型)，那么最佳实践是什么？一个例子是图书订单处理服务，它必须等待订单中的每一本书都被仓库处理，然后再
javascript - subscribe() 后获取返回变量的值
我使用下面的代码进行异步调用，我想知道在 getData() 函数中生成的 data 的值，但是，我得到 undefined 因为调用还没有解决。有什么办法可以解决吗？ getData(address
javascript - 无法获取未定义或空引用的属性 'subscribe'
我在订阅我的 HTML 页面中的下拉值更改时遇到实现 knockout Js 的问题。这是我的 HTML Request Types :
javascript - 异步使用 subscribe()
函数定义 resetComponent(){ console.log("1st"); ... this.background = { }; this.uploadMode = fals
android - @Subscribe 方法为同一事件调用多次
在我的代码中，我正在使用 @Subscribe 注释来监听事件: @Subscribe public void orderUpdate(OrderUpdateEvent event) 我的问题是，对于
javascript - .subscribe() 函数有什么作用？
我正在使用 Angular2 和 NodeJS 编写 API，我正在为我的 ِAPI 实现服务，该 API 应该获取任务列表并显示它。这是任务服务: import {Injectable} from
Angular 无法读取未定义的属性 'subscribe'
我正在尝试使用来自服务器的 json 响应创建动态菜单，但出现此错误: MenuComponent.html:4 ERROR TypeError: Cannot read property 'subs
Angular2 - 无法读取嵌套调用中未定义的属性 'subscribe'
我查看了许多资源，包括 this , this和 this ，但我一直无法达到预期的效果。我要做的就是验证用户(使用 firebase)，然后在验证后加载他们的配置文件并将其存储在变量 userPr

行者123

个人简介

我是一名优秀的程序员,十分优秀！

作者热门文章

滴滴打车优惠券免费领取

全站热门文章

首页

博学

6Ren·AI

商城

spring-boot - Spring WebFlux : Only one connection receive subscriber allowed