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/*
* Copyright 2022 Google LLC
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.google.android.libraries.mobiledatadownload;
import androidx.annotation.VisibleForTesting;
import com.google.common.base.Optional;
import com.google.common.collect.ImmutableList;
import com.google.common.util.concurrent.FutureCallback;
import com.google.common.util.concurrent.Futures;
import com.google.common.util.concurrent.ListenableFuture;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.util.Collection;
import java.util.Locale;
import java.util.concurrent.CancellationException;
import java.util.concurrent.ExecutionException;
import javax.annotation.Nullable;
/**
* Represents an exception that's an aggregate of multiple other exceptions.
*
* <p>The first aggregated exception in set as the cause (see {@link Exception#getCause}) of the
* {@link AggregateException}. The full list can be accessed with {@link #getFailures}.
*/
public final class AggregateException extends Exception {
private static final String SEPARATOR_HEADER = "--- Failure %d ----------------------------\n";
private static final String SEPARATOR = "-------------------------------------------";
/** The maximum number of causes to recursively print in an exception's message. */
private static final int MAX_CAUSE_DEPTH = 5;
private final ImmutableList<Throwable> failures;
private AggregateException(String message, Throwable cause, ImmutableList<Throwable> failures) {
super(message, cause);
this.failures = failures;
}
/** Returns the list of the aggregated failures. */
public ImmutableList<Throwable> getFailures() {
return failures;
}
/**
* Throws {@link AggregateException} if any of the future in {@code futures} fails with either
* {@link CancellationException} or {@link ExecutionException}.
*
* <p>The {@code callbackOptional}, if present, will be executed each time when a future inside
* {@code futures} completes.
*/
public static <T> void throwIfFailed(
Collection<ListenableFuture<T>> futures,
Optional<FutureCallback<T>> callbackOptional,
String message,
Object... args)
throws AggregateException {
ImmutableList.Builder<Throwable> builder = null;
for (ListenableFuture<T> future : futures) {
try {
T result = Futures.getDone(future);
if (callbackOptional.isPresent()) {
callbackOptional.get().onSuccess(result);
}
} catch (CancellationException | ExecutionException e) {
// Unwrap the cause of the execution exception, we will instead wrap it with the aggregate.
if (builder == null) {
builder = ImmutableList.builder();
}
Throwable unwrapped = unwrapException(e);
builder.add(unwrapped);
if (callbackOptional.isPresent()) {
callbackOptional.get().onFailure(unwrapped);
}
}
}
if (builder == null) {
return;
}
final ImmutableList<Throwable> failures = builder.build();
throw newInstance(failures, message, args);
}
/**
* Throws {@link AggregateException} if any of the future in {@code futures} fails with either
* {@link CancellationException} or {@link ExecutionException}.
*/
public static <T> void throwIfFailed(
Collection<ListenableFuture<T>> futures, String message, Object... args)
throws AggregateException {
throwIfFailed(futures, /* callbackOptional= */ Optional.absent(), message, args);
}
/**
* Consolidates completed futures into a single failed futures if any failures exist.
*
* <p>If there are no failures, a void future will be returned.
*
* <p>If there is a single failure, that failure will be returned.
*
* <p>If there are multiple failures, an AggregateException containing all failures will be
* returned.
*/
public static <T> ListenableFuture<Void> consolidateDoneFutures(
Collection<ListenableFuture<T>> futures, String message, Object... args) {
try {
// Check if any futures are failed.
throwIfFailed(futures, message, args);
} catch (AggregateException e) {
if (e.getFailures().size() == 1) {
return Futures.immediateFailedFuture(e.getFailures().get(0));
} else {
return Futures.immediateFailedFuture(e);
}
}
return Futures.immediateVoidFuture();
}
/** Constructs a new {@link AggregateException} with the given throwables. */
public static AggregateException newInstance(
ImmutableList<Throwable> failures, String message, Object... args) {
String prologue = String.format(Locale.US, message, args);
return new AggregateException(
failures.size() > 1
? throwablesToString(
prologue + "\n" + failures.size() + " failure(s) in total:\n", failures)
: prologue,
failures.get(0),
failures);
}
@VisibleForTesting
static Throwable unwrapException(Throwable t) {
Throwable cause = t.getCause();
if (cause == null) {
return t;
}
Class<?> clazz = t.getClass();
if (clazz.equals(ExecutionException.class)) {
return unwrapException(cause);
}
return t;
}
private static String throwablesToString(
@Nullable String prologue, ImmutableList<Throwable> throwables) {
try (StringWriter out = new StringWriter();
PrintWriter writer = new PrintWriter(out)) {
if (prologue != null) {
writer.println(prologue);
}
for (int i = 0; i < throwables.size(); i++) {
Throwable failure = throwables.get(i);
writer.printf(SEPARATOR_HEADER, (i + 1));
writer.println(throwableToString(failure));
}
writer.println(SEPARATOR);
return out.toString();
} catch (Throwable t) {
return "Failed to build string from throwables: " + t;
}
}
@VisibleForTesting
static String throwableToString(Throwable failure) {
return throwableToString(failure, /*depth=*/ 1);
}
private static String throwableToString(Throwable failure, int depth) {
String message = failure.getClass().getName() + ": " + failure.getMessage();
Throwable cause = failure.getCause();
if (cause != null) {
if (depth >= MAX_CAUSE_DEPTH) {
return message + "\n(...)";
}
return message + "\nCaused by: " + throwableToString(cause, depth + 1);
}
return message;
}
}
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