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The Java operations layer for the MongoDB Java Driver. Third parties can wrap this layer to provide custom higher-level APIs

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/*
 * Copyright 2008-present MongoDB, Inc.
 *
 * 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.mongodb.internal.async;

import com.mongodb.lang.Nullable;

import java.util.concurrent.atomic.AtomicBoolean;
import java.util.function.Predicate;


/**
 * See {@link AsyncRunnable}
 * 

* This class is not part of the public API and may be removed or changed at any time */ @FunctionalInterface public interface AsyncSupplier extends AsyncFunction { /** * This should not be called externally to this API. It should be * implemented as a lambda. To "finish" an async chain, use one of * the "finish" methods. * * @see #finish(SingleResultCallback) */ void unsafeFinish(SingleResultCallback callback); /** * This is the async variant of a supplier's get method. * This method must only be used when this AsyncSupplier corresponds * to a {@link java.util.function.Supplier} (and is therefore being * used within an async chain method lambda). * @param callback the callback */ default void getAsync(final SingleResultCallback callback) { finish(callback); } @Override default void unsafeFinish(@Nullable final Void value, final SingleResultCallback callback) { unsafeFinish(callback); } /** * Must be invoked at end of async chain or when executing a callback handler supplied by the caller. * * @see #thenApply(AsyncFunction) * @see #thenConsume(AsyncConsumer) * @see #onErrorIf(Predicate, AsyncFunction) * @param callback the callback provided by the method the chain is used in */ default void finish(final SingleResultCallback callback) { final AtomicBoolean callbackInvoked = new AtomicBoolean(false); try { this.unsafeFinish((v, e) -> { if (!callbackInvoked.compareAndSet(false, true)) { throw new AssertionError(String.format("Callback has been already completed. It could happen " + "if code throws an exception after invoking an async method. Value: %s", v), e); } callback.onResult(v, e); }); } catch (Throwable t) { if (!callbackInvoked.compareAndSet(false, true)) { throw t; } else { callback.completeExceptionally(t); } } } /** * @param function The async function to run after this supplier * @return the composition of this supplier and the function, a supplier * @param The return type of the resulting supplier */ default AsyncSupplier thenApply(final AsyncFunction function) { return (c) -> { this.finish((v, e) -> { if (e == null) { function.finish(v, c); } else { c.completeExceptionally(e); } }); }; } /** * @param consumer The async consumer to run after this supplier * @return the composition of this supplier and the consumer, a runnable */ default AsyncRunnable thenConsume(final AsyncConsumer consumer) { return (c) -> { this.unsafeFinish((v, e) -> { if (e == null) { consumer.finish(v, c); } else { c.completeExceptionally(e); } }); }; } /** * @param errorCheck A check, comparable to a catch-if/otherwise-rethrow * @param errorFunction The branch to execute if the error matches * @return The composition of this, and the conditional branch */ default AsyncSupplier onErrorIf( final Predicate errorCheck, final AsyncFunction errorFunction) { // finish is used here instead of unsafeFinish to ensure that // exceptions thrown from the callback are properly handled return (callback) -> this.finish((r, e) -> { if (e == null) { callback.complete(r); return; } boolean errorMatched; try { errorMatched = errorCheck.test(e); } catch (Throwable t) { t.addSuppressed(e); callback.completeExceptionally(t); return; } if (errorMatched) { errorFunction.finish(e, callback); } else { callback.completeExceptionally(e); } }); } }





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