com.google.api.core.ApiFutures Maven / Gradle / Ivy
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* Copyright 2017, Google Inc.
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package com.google.api.core;
import static com.google.common.util.concurrent.MoreExecutors.directExecutor;
import com.google.common.base.Function;
import com.google.common.collect.Iterables;
import com.google.common.util.concurrent.AsyncFunction;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import java.util.List;
import java.util.concurrent.Executor;
import javax.annotation.Nullable;
/** Static utility methods for the {@link ApiFuture} interface. */
public final class ApiFutures {
private ApiFutures() {}
/**
* Registers a callback to be run when the {@link ApiFuture}'s computation is complete or, if the
* computation is already complete, immediately.
*
* @param future The future attach the callback to
* @param callback The callback to invoke when future is completed
* @deprecated Use {@linkplain #addCallback(ApiFuture, ApiFutureCallback, Executor) the overload
* that requires an executor}. For identical behavior, pass {@link
* com.google.common.util.concurrent.MoreExecutors#directExecutor}, but consider whether
* another executor would be safer.
*/
@Deprecated
public static void addCallback(
final ApiFuture future, final ApiFutureCallback callback) {
addCallback(future, callback, directExecutor());
}
/**
* Registers a callback to be run when the {@link ApiFuture}'s computation is complete or, if the
* computation is already complete, immediately.
*
* Note that this method is a delegate of {@link Futures#addCallback(ListenableFuture,
* FutureCallback, Executor)}.
*
* @param future The future attach the callback to
* @param callback The callback to invoke when future is completed
* @param executor The executor to run callback when the future completes
* @see Futures#addCallback(ListenableFuture, FutureCallback, Executor)
*/
public static void addCallback(
final ApiFuture future, final ApiFutureCallback callback, Executor executor) {
Futures.addCallback(
listenableFutureForApiFuture(future),
new FutureCallback() {
@Override
public void onFailure(Throwable t) {
callback.onFailure(t);
}
@Override
public void onSuccess(V v) {
callback.onSuccess(v);
}
},
executor);
}
/**
* Returns an {@link ApiFuture} whose result is taken from the given primary input or, if the
* primary input fails with the given exceptionType, from the result provided by the callback.
*
* @param input The primary input {@code ApiFuture}
* @param exceptionType The exception type that triggers use of {@code fallback}
* @param callback The {@link ApiFunction} to be called if input fails with the expected exception
* type
* @return A future whose result is taken either from the given {@code input} or by the {@code
* callback}
* @deprecated Use {@linkplain #catching(ApiFuture, Class, ApiFunction, Executor) the overload
* that requires an executor}. For identical behavior, pass {@link
* com.google.common.util.concurrent.MoreExecutors#directExecutor}, but consider whether
* another executor would be safer.
*/
@Deprecated
public static ApiFuture catching(
ApiFuture input,
Class exceptionType,
ApiFunction callback) {
return catching(input, exceptionType, callback, directExecutor());
}
/**
* Returns an {@link ApiFuture} whose result is taken from the given primary input or, if the
* primary input fails with the given exceptionType, from the result provided by the callback.
*
* Note that this method is a delegate of {@link Futures#catching(ListenableFuture, Class,
* Function, Executor)}.
*
* @param input The primary input {@code ApiFuture}
* @param exceptionType The exception type that triggers use of {@code fallback}
* @param callback The {@link ApiFunction} to be called if input fails with the expected exception
* type
* @param executor The executor that runs {@code fallback} if {@code input} fails
* @return A future whose result is taken either from the given {@code input} or by the {@code
* callback}
* @see Futures#catching(ListenableFuture, Class, Function, Executor)
*/
public static ApiFuture catching(
ApiFuture input,
Class exceptionType,
ApiFunction callback,
Executor executor) {
ListenableFuture catchingFuture =
Futures.catching(
listenableFutureForApiFuture(input),
exceptionType,
new ApiFunctionToGuavaFunction(callback),
executor);
return new ListenableFutureToApiFuture(catchingFuture);
}
/**
* Returns a {@link ApiFuture} whose result is taken from the given primary input or, if the
* primary input fails with the given exceptionType, from the result provided by the callback.
*
* Note that this method is a delegate of {@link Futures#catchingAsync(ListenableFuture, Class,
* AsyncFunction, Executor)}
*
* @param input The primary input {@code ApiFuture}
* @param exceptionType The exception type that triggers use of {@code fallback}.
* @param callback The {@link ApiAsyncFunction} to be called if {@code input} fails with the
* expected * exception type.
* @param executor The executor that runs {@code fallback} if {@code input} fails
* @return A future whose result is taken either from the given {@code input} or by the {@code
* callback}
* @see Futures#catchingAsync(ListenableFuture, Class, AsyncFunction, Executor)
*/
@BetaApi
public static ApiFuture catchingAsync(
ApiFuture input,
Class exceptionType,
final ApiAsyncFunction callback,
Executor executor) {
ListenableFuture catchingFuture =
Futures.catchingAsync(
listenableFutureForApiFuture(input),
exceptionType,
new AsyncFunction() {
@Override
public ListenableFuture apply(X exception) throws Exception {
ApiFuture result = callback.apply(exception);
return listenableFutureForApiFuture(result);
}
},
executor);
return new ListenableFutureToApiFuture<>(catchingFuture);
}
/**
* Creates a {@code ApiFuture} which has its value set immediately upon construction.
*
* Note that this method is a delegate of {@link Futures#immediateFuture(Object)}.
*
* @param value The value set to the {@code ApiFuture} upon construction
* @return A future that holds {@code value}
* @see Futures#immediateFuture(Object)
*/
public static ApiFuture immediateFuture(V value) {
return new ListenableFutureToApiFuture<>(Futures.immediateFuture(value));
}
/**
* Returns a {@code ApiFuture} which has an exception set immediately upon construction.
*
* Note that this method is a delegate of {@link Futures#immediateFailedFuture(Throwable)}.
*
* @param throwable The exception set to the {@code ApiFuture} upon construction
* @return A future that holds an exception
* @see Futures#immediateFailedFuture(Throwable)
*/
public static ApiFuture immediateFailedFuture(Throwable throwable) {
return new ListenableFutureToApiFuture(Futures.immediateFailedFuture(throwable));
}
/**
* Creates a {@code ApiFuture} which is cancelled immediately upon construction, so that {@code
* isCancelled()} always returns {@code true}.
*
* Note that this method is a delegate of {@link Futures#immediateCancelledFuture()}.
*
* @return A cancelled future
* @see Futures#immediateCancelledFuture()
*/
public static ApiFuture immediateCancelledFuture() {
return new ListenableFutureToApiFuture(Futures.immediateCancelledFuture());
}
/**
* Returns a new {@code ApiFuture} whose result is derived from the result of the given {@code
* ApiFuture}.
*
* @param input The future to transform
* @param function A Function to transform the results of the provided future to the results of
* the returned future
* @return A future that holds result of the transformation
* @deprecated Use {@linkplain #transform(ApiFuture, ApiFunction, Executor) the overload that
* requires an executor}. For identical behavior, pass {@link
* com.google.common.util.concurrent.MoreExecutors#directExecutor}, but consider whether
* another executor would be safer.
*/
@Deprecated
public static ApiFuture transform(
ApiFuture input, final ApiFunction function) {
return transform(input, function, directExecutor());
}
/**
* Returns a new {@code ApiFuture} whose result is derived from the result of the given {@code
* ApiFuture}.
*
* Note that this method is a delegate of {@link Futures#transform(ListenableFuture, Function,
* Executor)}.
*
* @param input The future to transform
* @param function A Function to transform the results of the provided future to the results of
* the returned future.
* @param executor Executor to run the function in.
* @return A future that holds result of the transformation
* @see Futures#transform(ListenableFuture, Function, Executor)
*/
public static ApiFuture transform(
ApiFuture input,
final ApiFunction function,
Executor executor) {
return new ListenableFutureToApiFuture<>(
Futures.transform(
listenableFutureForApiFuture(input),
new ApiFunctionToGuavaFunction(function),
executor));
}
/**
* Creates a new {@code ApiFuture} whose value is a list containing the values of all its input
* futures, if all succeed.
*
* The list of results is in the same order as the input list.
*
*
Note that this method is a delegate of {@link Futures#allAsList(Iterable)}.
*
* @param futures Futures to combine
* @return A future that provides a list of the results of the component futures
* @see Futures#allAsList(Iterable)
*/
public static ApiFuture> allAsList(
Iterable> futures) {
return new ListenableFutureToApiFuture<>(
Futures.allAsList(
Iterables.transform(
futures,
new Function, ListenableFuture>() {
public ListenableFuture apply(ApiFuture apiFuture) {
return listenableFutureForApiFuture(apiFuture);
}
})));
}
/**
* Creates a new {@code ApiFuture} whose value is a list containing the values of all its
* successful input futures. The list of results is in the same order as the input list, and if
* any of the provided futures fails or is canceled, its corresponding position will contain
* {@code null} (which is indistinguishable from the future having a successful value of {@code
* null}).
*
* The list of results is in the same order as the input list.
*
*
Note that this method is a delegate of {@link Futures#successfulAsList(Iterable)}.
*
* @param futures Futures to combine
* @return A future that provides a list of the results of the component futures
* @see Futures#successfulAsList(Iterable)
*/
@BetaApi
public static ApiFuture> successfulAsList(
Iterable> futures) {
return new ListenableFutureToApiFuture<>(
Futures.successfulAsList(
Iterables.transform(
futures,
new Function, ListenableFuture>() {
public ListenableFuture apply(ApiFuture apiFuture) {
return listenableFutureForApiFuture(apiFuture);
}
})));
}
/**
* Returns a new {@code ApiFuture} whose result is asynchronously derived from the result of the
* given {@code ApiFuture}. If the given {@code Future} fails, the returned {@code ApiFuture}
* fails with the same exception (and the function is not invoked).
*
* @param input The future to transform
* @param function A function to transform the result of the input future to the result of the
* output future
* @return A future that holds result of the function (if the input succeeded) or the original
* input's failure (if not)
* @deprecated Use {@linkplain #transformAsync(ApiFuture, ApiAsyncFunction, Executor)}, the
* overload that requires an executor. For identical behavior, pass {@link
* com.google.common.util.concurrent.MoreExecutors#directExecutor}, but consider whether
* another executor would be safer.
*/
@Deprecated
public static ApiFuture transformAsync(
ApiFuture input, final ApiAsyncFunction function) {
return transformAsync(input, function, directExecutor());
}
/**
* Returns a new {@code ApiFuture} whose result is asynchronously derived from the result of the
* given {@code ApiFuture}. If the given {@code Future} fails, the returned {@code ApiFuture}
* fails with the same exception (and the function is not invoked).
*
* Note that this method is a delegate of {@link Futures#transformAsync(ListenableFuture,
* AsyncFunction, Executor)}.
*
* @param input The future to transform
* @param function A function to transform the result of the input future to the result of the
* output future
* @param executor Executor to run the function in.
* @return A future that holds result of the function (if the input succeeded) or the original
* input's failure (if not)
* @see Futures#transformAsync(ListenableFuture, AsyncFunction, Executor)
*/
public static ApiFuture transformAsync(
ApiFuture input, final ApiAsyncFunction function, Executor executor) {
ListenableFuture listenableInput = listenableFutureForApiFuture(input);
ListenableFuture listenableOutput =
Futures.transformAsync(
listenableInput,
new AsyncFunction() {
@Override
public ListenableFuture apply(I input) throws Exception {
return listenableFutureForApiFuture(function.apply(input));
}
},
executor);
return new ListenableFutureToApiFuture<>(listenableOutput);
}
private static ListenableFuture listenableFutureForApiFuture(ApiFuture apiFuture) {
ListenableFuture listenableFuture;
if (apiFuture instanceof AbstractApiFuture) {
// prefer to use the wrapped ListenableFuture to reduce the number of layers
listenableFuture = ((AbstractApiFuture) apiFuture).getInternalListenableFuture();
} else {
listenableFuture = new ApiFutureToListenableFuture(apiFuture);
}
return listenableFuture;
}
private static class ApiFunctionToGuavaFunction
implements com.google.common.base.Function {
private ApiFunction f;
public ApiFunctionToGuavaFunction(ApiFunction f) {
this.f = f;
}
@Nullable
@Override
public V apply(@Nullable X input) {
return f.apply(input);
}
}
}