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问题[kotlin-coroutines](coding)

Martin Hope
Ken Kiarie
Asked: 2025-04-05 20:07:36 +0800 CST
  • 8

遇到了一个例子，模拟访问一个慢速数据库以获取与可通过更慢的网络资源访问的配置文件相关联的用户标识符流：

fun getAllUserIds():Flow<Int>{
    return flow{
        repeat(3){
            delay(200.milliseconds)
            log("Emitting!")
            emit(it)
            }
         } 
      }

suspend fun getProfileFromNetwork(id:Int):String{
    delay(2.seconds)
    return "Profile[$id]"
  }

fun main(){
    val ids = getAllUserIds()
    runBlocking{
        ids
            .map{getProfileFromNetwork(it)}
            .collect{log("Got $it")}
        }
  }

ID 的发布和配置文件的请求是相互交织的。我该如何通过为流程中的每个元素的处理生成新的协程来优化这一点？

kotlin-coroutines
Martin Hope
Jakub Bochenski
Asked: 2025-02-13 23:35:24 +0800 CST
  • 6

这里没有记录https://www.jooq.org/doc/latest/manual/sql-execution/transaction-management/

它仅向您显示未捕获的异常将导致回滚。

问题是RollbackToSavepointStep不是Publisher。

是否可以通过编程方式回滚？

如果我尝试的dsl().rollback().executeAsync().await()话我会得到：

DetachedException: Attempt to execute a blocking method (e.g. Query.execute() or ResultQuery.fetch()) when only an R2BDC ConnectionFactory was configured. jOOQ's RowCountQuery and ResultQuery extend Publisher, which allows for reactive streams implementations to subscribe to the results of a jOOQ query. Simply embed your query in the stream, e.g. using Flux.from(query). See also: https://www.jooq.org/doc/latest/manual/sql-execution/fetching/reactive-fetching/
kotlin-coroutines
Martin Hope
Shyam Patel
Asked: 2024-05-29 14:13:19 +0800 CST
  • 5

我试图理解为什么异常会在没有被?async包围的情况下沿着层次结构传递。为什么在处理异常时coroutineScope不需要这样？coroutineScopelaunch

fun main() {
    runBlocking {
        this.launch {// case 1
            try {
                throw java.lang.IndexOutOfBoundsException()
            } catch (e: Exception) {
                println("Caught IndexOutOfBoundsException")
            }
        }
        try {
            coroutineScope {
                val deferred = async {// case 2
                    throw ArithmeticException()
                }
                deferred.await()

            }
        } catch (e: ArithmeticException) {
            println("Caught ArithmeticException")
        }
        try {
            val deferred = async {//case 3
                throw ArithmeticException()
            }
            deferred.await()
        } catch (e: Exception) {
            println("Caught ArithmeticException but passed to root as well")
        }
    }
}

我当前的输出如下：

Caught IndexOutOfBoundsException
Caught ArithmeticException
Caught ArithmeticException but passed to root as well
Exception in thread "main" java.lang.ArithmeticException
    at TryItYourself3Kt$main$1$deferred$1.invokeSuspend(TryItYourself3.kt:26)
    at kotlin.coroutines.jvm.internal.BaseContinuationImpl.resumeWith(ContinuationImpl.kt:33)
    at kotlinx.coroutines.DispatchedTask.run(DispatchedTask.kt:104)
    at kotlinx.coroutines.EventLoopImplBase.processNextEvent(EventLoop.common.kt:277)
    at kotlinx.coroutines.BlockingCoroutine.joinBlocking(Builders.kt:95)
    at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking(Builders.kt:69)
    at kotlinx.coroutines.BuildersKt.runBlocking(Unknown Source)
    at kotlinx.coroutines.BuildersKt__BuildersKt.runBlocking$default(Builders.kt:48)
    at kotlinx.coroutines.BuildersKt.runBlocking$default(Unknown Source)
    at TryItYourself3Kt.main(TryItYourself3.kt:5)
    at TryItYourself3Kt.main(TryItYourself3.kt)

Process finished with exit code 1
kotlin-coroutines