WebTestClient 返回 IllegalStateException：block()/blockFirst()/blockLast() 正在阻塞，线程中不支持

Question

以下功能：

private Boolean canDoIt(Parameter param) {
  return myService
      .getMyObjectInReactiveWay(param)
      .map(myObject -> myService.checkMyObjectInImperativeWay(myObject))
      .block();
}

在运行时工作正常，但是当使用它测试使用它的流程时，WebTestClient出现以下错误：

java.lang.IllegalStateException: block()/blockFirst()/blockLast() are blocking, which is not supported in thread parallel-1
    at reactor.core.publisher.BlockingSingleSubscriber.blockingGet(BlockingSingleSubscriber.java:83) ~[reactor-core-3.4.1.jar:3.4.1]
    Suppressed: reactor.core.publisher.FluxOnAssembly$OnAssemblyException: 
Assembly trace from producer [reactor.core.publisher.MonoFlatMap] :
    reactor.core.publisher.Mono.flatMap

我知道我不应该使用block()，但我别无选择：该函数必须返回 a Boolean（而不是 a Mono<Boolean>）。也许有另一种不使用block().

有没有办法让我WebTestClient不抛出该错误？

使用Reactor Core版本3.4.6。

Answer 1

我验证我的评论。block()检查调用线程是否与阻塞代码兼容（反应器外部的线程，或特定反应器调度程序的线程，例如Schedulers.boundedElastic()）。

有两种方法可以处理反应式堆栈中间的阻塞调用：

• 在您要阻止的发布者上使用共享运算符。请注意，共享运算符会在内部缓存该值。
• 使用或强制block()在阻塞兼容调度程序上执行调用。请注意，不应在直接调用 的发布者上调用此运算符，而应在将“包装”块调用的发布者上调用此运算符（请参见下面的示例）。scheduleOnpublishOnblock()

一些参考：

• 调度程序 API 文档总结了可用的调度程序类型，并说明哪些调度程序是为阻止调用而设计的。
• 有关阻止调用包装的参考指南部分
• share() 操作符文档

一个最小的可重现示例（在 v3.4.6 上测试）给出了以下输出：

Ok context: not running from reactor Threads
value is true
Problematic stack: working with scheduler not compatible with blocking call
ERROR: block()/blockFirst()/blockLast() are blocking, which is not supported in thread parallel-2
Bad way to subscribe on a blocking compatible scheduler
ERROR: block()/blockFirst()/blockLast() are blocking, which is not supported in thread parallel-4
Bad way to publish on blocking compatible scheduler
ERROR: block()/blockFirst()/blockLast() are blocking, which is not supported in thread parallel-6
Possible workaround: share the reactive stream before blocking on it
It worked
Right way to subscribe on blocking compatible scheduler
It worked
Right way to publish on blocking compatible scheduler
It worked

代码如下：

Ok context: not running from reactor Threads
value is true
Problematic stack: working with scheduler not compatible with blocking call
ERROR: block()/blockFirst()/blockLast() are blocking, which is not supported in thread parallel-2
Bad way to subscribe on a blocking compatible scheduler
ERROR: block()/blockFirst()/blockLast() are blocking, which is not supported in thread parallel-4
Bad way to publish on blocking compatible scheduler
ERROR: block()/blockFirst()/blockLast() are blocking, which is not supported in thread parallel-6
Possible workaround: share the reactive stream before blocking on it
It worked
Right way to subscribe on blocking compatible scheduler
It worked
Right way to publish on blocking compatible scheduler
It worked