com.firefly.utils.concurrent.Promise Maven / Gradle / Ivy
package com.firefly.utils.concurrent;
import java.util.concurrent.CompletableFuture;
/**
*
* A callback abstraction that handles completed/failed events of asynchronous
* operations.
*
*
* @param
* the type of the context object
*/
public interface Promise {
/**
*
* Callback invoked when the operation completes.
*
*
* @param result
* the context
* @see #failed(Throwable)
*/
default void succeeded(C result) {
}
/**
*
* Callback invoked when the operation fails.
*
*
* @param x
* the reason for the operation failure
*/
default void failed(Throwable x) {
}
/**
*
* Empty implementation of {@link Promise}.
*
*
* @param
* the type of the result
*/
class Adapter implements Promise {
@Override
public void succeeded(U result) {
}
@Override
public void failed(Throwable x) {
x.printStackTrace();
}
}
/**
*
* Creates a promise from the given incomplete CompletableFuture.
*
*
* When the promise completes, either succeeding or failing, the
* CompletableFuture is also completed, respectively via
* {@link CompletableFuture#complete(Object)} or
* {@link CompletableFuture#completeExceptionally(Throwable)}.
*
*
* @param completable
* the CompletableFuture to convert into a promise
* @return a promise that when completed, completes the given
* CompletableFuture
* @param
* the type of the result
*/
@SuppressWarnings("unchecked")
static Promise from(CompletableFuture completable) {
if (completable instanceof Promise)
return (Promise) completable;
return new Promise() {
@Override
public void succeeded(T result) {
completable.complete(result);
}
@Override
public void failed(Throwable x) {
completable.completeExceptionally(x);
}
};
}
/**
*
* A CompletableFuture that is also a Promise.
*
*
* @param
* the type of the result
*/
class Completable extends CompletableFuture implements Promise {
@Override
public void succeeded(S result) {
complete(result);
}
@Override
public void failed(Throwable x) {
completeExceptionally(x);
}
}
}