akka.dispatch.Future.scala Maven / Gradle / Ivy
/*
* Copyright (C) 2009-2019 Lightbend Inc.
*/
package akka.dispatch
import scala.runtime.{ AbstractPartialFunction, BoxedUnit }
import akka.japi.{ Procedure, Function => JFunc, Option => JOption }
import scala.concurrent.{ ExecutionContext, ExecutionContextExecutor, ExecutionContextExecutorService, Future, Promise }
import java.lang.{ Iterable => JIterable }
import java.util.{ LinkedList => JLinkedList }
import java.util.concurrent.{ Callable, Executor, ExecutorService }
import scala.util.{ Failure, Success, Try }
import java.util.concurrent.CompletionStage
import java.util.concurrent.CompletableFuture
import akka.compat
import akka.util.unused
import com.github.ghik.silencer.silent
/**
* ExecutionContexts is the Java API for ExecutionContexts
*/
object ExecutionContexts {
/**
* Returns a new ExecutionContextExecutor which will delegate execution to the underlying Executor,
* and which will use the default error reporter.
*
* @param executor the Executor which will be used for the ExecutionContext
* @return a new ExecutionContext
*/
def fromExecutor(executor: Executor): ExecutionContextExecutor =
ExecutionContext.fromExecutor(executor)
/**
* Returns a new ExecutionContextExecutor which will delegate execution to the underlying Executor,
* and which will use the provided error reporter.
*
* @param executor the Executor which will be used for the ExecutionContext
* @param errorReporter a Procedure that will log any exceptions passed to it
* @return a new ExecutionContext
*/
def fromExecutor(executor: Executor, errorReporter: Procedure[Throwable]): ExecutionContextExecutor =
ExecutionContext.fromExecutor(executor, errorReporter.apply)
/**
* Returns a new ExecutionContextExecutorService which will delegate execution to the underlying ExecutorService,
* and which will use the default error reporter.
*
* @param executorService the ExecutorService which will be used for the ExecutionContext
* @return a new ExecutionContext
*/
def fromExecutorService(executorService: ExecutorService): ExecutionContextExecutorService =
ExecutionContext.fromExecutorService(executorService)
/**
* Returns a new ExecutionContextExecutorService which will delegate execution to the underlying ExecutorService,
* and which will use the provided error reporter.
*
* @param executorService the ExecutorService which will be used for the ExecutionContext
* @param errorReporter a Procedure that will log any exceptions passed to it
* @return a new ExecutionContext
*/
def fromExecutorService(
executorService: ExecutorService,
errorReporter: Procedure[Throwable]): ExecutionContextExecutorService =
ExecutionContext.fromExecutorService(executorService, errorReporter.apply)
/**
* @return a reference to the global ExecutionContext
*/
def global(): ExecutionContextExecutor = ExecutionContext.global
/**
* WARNING: Not A General Purpose ExecutionContext!
*
* This is an execution context which runs everything on the calling thread.
* It is very useful for actions which are known to be non-blocking and
* non-throwing in order to save a round-trip to the thread pool.
*/
private[akka] object sameThreadExecutionContext extends ExecutionContext with BatchingExecutor {
override protected def unbatchedExecute(runnable: Runnable): Unit = runnable.run()
override protected def resubmitOnBlock: Boolean = false // No point since we execute on same thread
override def reportFailure(t: Throwable): Unit =
throw new IllegalStateException("exception in sameThreadExecutionContext", t)
}
}
/**
* Futures is the Java API for Futures and Promises
*/
object Futures {
import scala.collection.JavaConverters.iterableAsScalaIterableConverter
/**
* Starts an asynchronous computation and returns a `Future` object with the result of that computation.
*
* The result becomes available once the asynchronous computation is completed.
*
* @param body the asynchronous computation
* @param executor the execution context on which the future is run
* @return the `Future` holding the result of the computation
*/
def future[T](body: Callable[T], executor: ExecutionContext): Future[T] = Future(body.call)(executor)
/**
* Creates a promise object which can be completed with a value.
*
* @return the newly created `Promise` object
*/
def promise[T](): Promise[T] = Promise[T]()
/**
* creates an already completed Promise with the specified exception
*/
def failed[T](exception: Throwable): Future[T] = Future.failed(exception)
/**
* Creates an already completed Promise with the specified result
*/
def successful[T](result: T): Future[T] = Future.successful(result)
/**
* Creates an already completed CompletionStage with the specified exception
*/
def failedCompletionStage[T](ex: Throwable): CompletionStage[T] = {
val f = CompletableFuture.completedFuture[T](null.asInstanceOf[T])
f.obtrudeException(ex)
f
}
/**
* Returns a Future that will hold the optional result of the first Future with a result that matches the predicate
*/
def find[T <: AnyRef](
futures: JIterable[Future[T]],
predicate: JFunc[T, java.lang.Boolean],
executor: ExecutionContext): Future[JOption[T]] = {
implicit val ec = executor
compat.Future.find[T](futures.asScala)(predicate.apply(_))(executor).map(JOption.fromScalaOption)
}
/**
* Returns a Future to the result of the first future in the list that is completed
*/
def firstCompletedOf[T <: AnyRef](futures: JIterable[Future[T]], executor: ExecutionContext): Future[T] =
Future.firstCompletedOf(futures.asScala)(executor)
/**
* A non-blocking fold over the specified futures, with the start value of the given zero.
* The fold is performed on the thread where the last future is completed,
* the result will be the first failure of any of the futures, or any failure in the actual fold,
* or the result of the fold.
*/
def fold[T <: AnyRef, R <: AnyRef](
zero: R,
futures: JIterable[Future[T]],
fun: akka.japi.Function2[R, T, R],
executor: ExecutionContext): Future[R] =
compat.Future.fold(futures.asScala)(zero)(fun.apply)(executor)
/**
* Reduces the results of the supplied futures and binary function.
*/
def reduce[T <: AnyRef, R >: T](
futures: JIterable[Future[T]],
fun: akka.japi.Function2[R, T, R],
executor: ExecutionContext): Future[R] =
compat.Future.reduce[T, R](futures.asScala)(fun.apply)(executor)
/**
* Simple version of [[#traverse]]. Transforms a JIterable[Future[A]] into a Future[JIterable[A]].
* Useful for reducing many Futures into a single Future.
*/
def sequence[A](in: JIterable[Future[A]], executor: ExecutionContext): Future[JIterable[A]] = {
implicit val d = executor
in.asScala.foldLeft(Future(new JLinkedList[A]())) { (fr, fa) =>
for (r <- fr; a <- fa) yield { r.add(a); r }
}
}
/**
* Transforms a JIterable[A] into a Future[JIterable[B]] using the provided Function A => Future[B].
* This is useful for performing a parallel map. For example, to apply a function to all items of a list
* in parallel.
*/
def traverse[A, B](in: JIterable[A], fn: JFunc[A, Future[B]], executor: ExecutionContext): Future[JIterable[B]] = {
implicit val d = executor
in.asScala.foldLeft(Future(new JLinkedList[B]())) { (fr, a) =>
val fb = fn(a)
for (r <- fr; b <- fb) yield { r.add(b); r }
}
}
}
/**
* This class contains bridge classes between Scala and Java.
* Internal use only.
*/
object japi {
@deprecated("Do not use this directly, use subclasses of this", "2.0")
class CallbackBridge[-T] extends AbstractPartialFunction[T, BoxedUnit] {
override final def isDefinedAt(t: T): Boolean = true
override final def apply(t: T): BoxedUnit = {
internal(t)
BoxedUnit.UNIT
}
protected def internal(@unused result: T): Unit = ()
}
@deprecated("Do not use this directly, use 'Recover'", "2.0")
class RecoverBridge[+T] extends AbstractPartialFunction[Throwable, T] {
override final def isDefinedAt(t: Throwable): Boolean = true
override final def apply(t: Throwable): T = internal(t)
protected def internal(@unused result: Throwable): T = null.asInstanceOf[T]
}
@deprecated("Do not use this directly, use subclasses of this", "2.0")
class BooleanFunctionBridge[-T] extends scala.Function1[T, Boolean] {
override final def apply(t: T): Boolean = internal(t)
protected def internal(@unused result: T): Boolean = false
}
@deprecated("Do not use this directly, use subclasses of this", "2.0")
class UnitFunctionBridge[-T] extends (T => BoxedUnit) {
final def apply$mcLJ$sp(l: Long): BoxedUnit = { internal(l.asInstanceOf[T]); BoxedUnit.UNIT }
final def apply$mcLI$sp(i: Int): BoxedUnit = { internal(i.asInstanceOf[T]); BoxedUnit.UNIT }
final def apply$mcLF$sp(f: Float): BoxedUnit = { internal(f.asInstanceOf[T]); BoxedUnit.UNIT }
final def apply$mcLD$sp(d: Double): BoxedUnit = { internal(d.asInstanceOf[T]); BoxedUnit.UNIT }
override final def apply(t: T): BoxedUnit = { internal(t); BoxedUnit.UNIT }
protected def internal(@unused result: T): Unit = ()
}
}
/**
* Callback for when a Future is completed successfully
* SAM (Single Abstract Method) class
*
* Java API
*/
@silent
abstract class OnSuccess[-T] extends japi.CallbackBridge[T] {
protected final override def internal(result: T) = onSuccess(result)
/**
* This method will be invoked once when/if a Future that this callback is registered on
* becomes successfully completed
*/
@throws(classOf[Throwable])
def onSuccess(result: T): Unit
}
/**
* Callback for when a Future is completed with a failure
* SAM (Single Abstract Method) class
*
* Java API
*/
@silent
abstract class OnFailure extends japi.CallbackBridge[Throwable] {
protected final override def internal(failure: Throwable) = onFailure(failure)
/**
* This method will be invoked once when/if a Future that this callback is registered on
* becomes completed with a failure
*/
@throws(classOf[Throwable])
def onFailure(failure: Throwable): Unit
}
/**
* Callback for when a Future is completed with either failure or a success
* SAM (Single Abstract Method) class
*
* Java API
*/
@silent
abstract class OnComplete[-T] extends japi.CallbackBridge[Try[T]] {
protected final override def internal(value: Try[T]): Unit = value match {
case Failure(t) => onComplete(t, null.asInstanceOf[T])
case Success(r) => onComplete(null, r)
}
/**
* This method will be invoked once when/if a Future that this callback is registered on
* becomes completed with a failure or a success.
* In the case of success then "failure" will be null, and in the case of failure the "success" will be null.
*/
@throws(classOf[Throwable])
def onComplete(failure: Throwable, success: T): Unit
}
/**
* Callback for the Future.recover operation that conditionally turns failures into successes.
*
* SAM (Single Abstract Method) class
*
* Java API
*/
@silent
abstract class Recover[+T] extends japi.RecoverBridge[T] {
protected final override def internal(result: Throwable): T = recover(result)
/**
* This method will be invoked once when/if the Future this recover callback is registered on
* becomes completed with a failure.
*
* @return a successful value for the passed in failure
* Throws the passed in failure to propagate it.
*
* Java API
*/
@throws(classOf[Throwable])
def recover(failure: Throwable): T
}
/**
* Java API (not recommended):
* Callback for the Future.filter operation that creates a new Future which will
* conditionally contain the success of another Future.
*
* Unfortunately it is not possible to express the type of a Scala filter in
* Java: Function1[T, Boolean], where “Boolean” is the primitive type. It is
* possible to use `Future.filter` by constructing such a function indirectly:
*
* {{{
* import static akka.dispatch.Filter.filterOf;
* Future f = ...;
* f.filter(filterOf(new Function() {
* @Override
* public Boolean apply(String s) {
* ...
* }
* }));
* }}}
*
* However, `Future.filter` exists mainly to support Scala’s for-comprehensions,
* thus Java users should prefer `Future.map`, translating non-matching values
* to failure cases.
*/
object Filter {
def filterOf[T](f: akka.japi.Function[T, java.lang.Boolean]): (T => Boolean) =
new Function1[T, Boolean] { def apply(result: T): Boolean = f(result).booleanValue() }
}
/**
* Callback for the Future.foreach operation that will be invoked if the Future that this callback
* is registered on becomes completed with a success. This method is essentially the same operation
* as onSuccess.
*
* SAM (Single Abstract Method) class
* Java API
*/
@silent
abstract class Foreach[-T] extends japi.UnitFunctionBridge[T] {
override final def internal(t: T): Unit = each(t)
/**
* This method will be invoked once when/if a Future that this callback is registered on
* becomes successfully completed
*/
@throws(classOf[Throwable])
def each(result: T): Unit
}
/**
* Callback for the Future.map and Future.flatMap operations that will be invoked
* if the Future that this callback is registered on becomes completed with a success.
* This callback is the equivalent of an akka.japi.Function
*
* Override "apply" normally, or "checkedApply" if you need to throw checked exceptions.
*
* SAM (Single Abstract Method) class
*
* Java API
*/
abstract class Mapper[-T, +R] extends scala.runtime.AbstractFunction1[T, R] {
/**
* Override this method to perform the map operation, by default delegates to "checkedApply"
* which by default throws an UnsupportedOperationException.
*/
def apply(parameter: T): R = checkedApply(parameter)
/**
* Override this method if you need to throw checked exceptions
*
* Throws UnsupportedOperation by default.
*/
@throws(classOf[Throwable])
def checkedApply(@unused parameter: T): R =
throw new UnsupportedOperationException("Mapper.checkedApply has not been implemented")
}
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