当响应不包含媒体类型标头时，Spring webclient 抛出“仅允许一个连接接收订阅者”

Posted 2023-02-16

【中文标题】当响应不包含媒体类型标头时，Spring webclient 抛出“仅允许一个连接接收订阅者”

【英文标题】：Spring webclient throws "Only one connection receive subscriber allowed" when response does not contain media type header

【发布时间】：2019-04-08 05:21:49

【问题描述】：

参考模拟问题的测试用例。 https://github.com/nischit7/my-exp-webflux-stream/blob/master/src/test/java/com/example/spring/stream/controller/MoreThanOnSubscriberTest.java

本质上，我提出了一个模拟服务器，它应该返回 NO 媒体类型标头。

在运行该测试时，我收到一个错误 - java.lang.IllegalStateException: 只允许一个连接接收订阅者。

at reactor.netty.channel.FluxReceive.startReceiver(FluxReceive.java:277)
at reactor.netty.channel.FluxReceive.subscribe(FluxReceive.java:127)
at reactor.core.publisher.FluxMap.subscribe(FluxMap.java:62)
at reactor.netty.ByteBufFlux.subscribe(ByteBufFlux.java:290)
at reactor.core.publisher.FluxMap.subscribe(FluxMap.java:62)
at reactor.core.publisher.FluxMap.subscribe(FluxMap.java:62)
at reactor.core.publisher.Flux.subscribe(Flux.java:7734)
at reactor.core.publisher.FluxConcatArray$ConcatArraySubscriber.onComplete(FluxConcatArray.java:207)
at reactor.core.publisher.MonoIgnoreElements$IgnoreElementsSubscriber.onComplete(MonoIgnoreElements.java:81)
at reactor.core.publisher.MonoIgnoreElements$IgnoreElementsSubscriber.onComplete(MonoIgnoreElements.java:81)
at reactor.core.publisher.Operators$MultiSubscriptionSubscriber.onComplete(Operators.java:1713)
at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:136)
at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:136)
at reactor.core.publisher.FluxMap$MapSubscriber.onComplete(FluxMap.java:136)
at reactor.netty.channel.FluxReceive.terminateReceiver(FluxReceive.java:378)
at reactor.netty.channel.FluxReceive.drainReceiver(FluxReceive.java:202)
at reactor.netty.channel.FluxReceive.onInboundComplete(FluxReceive.java:343)
at reactor.netty.channel.ChannelOperations.onInboundComplete(ChannelOperations.java:325)
at reactor.netty.channel.ChannelOperations.terminate(ChannelOperations.java:372)
at reactor.netty.http.client.HttpClientOperations.onInboundNext(HttpClientOperations.java:522)
at reactor.netty.channel.ChannelOperationsHandler.channelRead(ChannelOperationsHandler.java:141)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:102)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
at io.netty.channel.CombinedChannelDuplexHandler$DelegatingChannelHandlerContext.fireChannelRead(CombinedChannelDuplexHandler.java:438)
at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:310)
at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:284)
at io.netty.channel.CombinedChannelDuplexHandler.channelRead(CombinedChannelDuplexHandler.java:253)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1434)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:965)
at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163)
at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:628)
at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:563)
at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:480)
at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:442)
at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:884)
at java.lang.Thread.run(Thread.java:748)
Suppressed: java.lang.Exception: #block terminated with an error
    at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:93)
    at reactor.core.publisher.Mono.block(Mono.java:1475)
    at com.example.spring.stream.controller.MoreThanOnSubscriberTest.moreThanOneSubscriberError(MoreThanOnSubscriberTest.java:83)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
    at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
    at com.intellij.junit4.JUnit4IdeaTestRunner.startRunnerWithArgs(JUnit4IdeaTestRunner.java:68)
    at com.intellij.rt.execution.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:47)
    at com.intellij.rt.execution.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:242)
    at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:70)

注意该测试类中的第 69 行。我是故意评论的。现在取消注释该行并重新运行测试用例。这一次，应该成功了。再次注释该行。

现在要注意另一件有趣的事情。当您将 spring-webflux 的版本更改为 5.0.10.RELEASE 时，您应该会看到它成功。将spring-webflix的版本改成5.1.1.RELEASE，会失败。 很明显，有些事情发生了变化。 我确实看到 spring 找不到内容类型的响应标头并将其默认为八位字节流。之后我没有进一步挖掘，为什么它会失败。

感谢任何帮助。

【参考方案1】：

现在看来这个问题已经解决了。我已经在 spring 社区https://jira.spring.io/browse/SPR-17482 上记录了这个错误。勾选已标记为已解决，并在 spring-webflux 5.1.3 中进行了修复。