com.arangodb.shaded.vertx.core.AsyncResult Maven / Gradle / Ivy
/*
* Copyright (c) 2011-2019 Contributors to the Eclipse Foundation
*
* This program and the accompanying materials are made available under the
* terms of the Eclipse Public License 2.0 which is available at
* http://www.eclipse.org/legal/epl-2.0, or the Apache License, Version 2.0
* which is available at https://www.apache.org/licenses/LICENSE-2.0.
*
* SPDX-License-Identifier: EPL-2.0 OR Apache-2.0
*/
package com.arangodb.shaded.vertx.core;
import java.util.function.Function;
/**
* Encapsulates the result of an asynchronous operation.
*
* Many operations in Vert.x APIs provide results back by passing an instance of this in a {@link com.arangodb.shaded.vertx.core.Handler}.
*
* The result can either have failed or succeeded.
*
* If it failed then the cause of the failure is available with {@link #cause}.
*
* If it succeeded then the actual result is available with {@link #result}
*
* @author Tim Fox
*/
public interface AsyncResult {
/**
* The result of the operation. This will be null if the operation failed.
*
* @return the result or null if the operation failed.
*/
T result();
/**
* A Throwable describing failure. This will be null if the operation succeeded.
*
* @return the cause or null if the operation succeeded.
*/
Throwable cause();
/**
* Did it succeed?
*
* @return true if it succeded or false otherwise
*/
boolean succeeded();
/**
* Did it fail?
*
* @return true if it failed or false otherwise
*/
boolean failed();
/**
* Apply a {@code mapper} function on this async result.
*
* The {@code mapper} is called with the completed value and this mapper returns a value. This value will complete the result returned by this method call.
*
* When this async result is failed, the failure will be propagated to the returned async result and the {@code mapper} will not be called.
*
* @param mapper the mapper function
* @return the mapped async result
*/
default AsyncResult map(Function mapper) {
if (mapper == null) {
throw new NullPointerException();
}
return new AsyncResult() {
@Override
public U result() {
if (succeeded()) {
return mapper.apply(AsyncResult.this.result());
} else {
return null;
}
}
@Override
public Throwable cause() {
return AsyncResult.this.cause();
}
@Override
public boolean succeeded() {
return AsyncResult.this.succeeded();
}
@Override
public boolean failed() {
return AsyncResult.this.failed();
}
};
}
/**
* Map the result of this async result to a specific {@code value}.
*
* When this async result succeeds, this {@code value} will succeeed the async result returned by this method call.
*
* When this async result fails, the failure will be propagated to the returned async result.
*
* @param value the value that eventually completes the mapped async result
* @return the mapped async result
*/
default AsyncResult map(V value) {
return map(t -> value);
}
/**
* Map the result of this async result to {@code null}.
*
* This is a convenience for {@code asyncResult.map((T) null)} or {@code asyncResult.map((Void) null)}.
*
* When this async result succeeds, {@code null} will succeeed the async result returned by this method call.
*
* When this async result fails, the failure will be propagated to the returned async result.
*
* @return the mapped async result
*/
default AsyncResult mapEmpty() {
return map((V)null);
}
/**
* Apply a {@code mapper} function on this async result.
*
* The {@code mapper} is called with the failure and this mapper returns a value. This value will complete the result returned by this method call.
*
* When this async result is succeeded, the value will be propagated to the returned async result and the {@code mapper} will not be called.
*
* @param mapper the mapper function
* @return the mapped async result
*/
default AsyncResult otherwise(Function mapper) {
if (mapper == null) {
throw new NullPointerException();
}
return new AsyncResult() {
@Override
public T result() {
if (AsyncResult.this.succeeded()) {
return AsyncResult.this.result();
} else if (AsyncResult.this.failed()) {
return mapper.apply(AsyncResult.this.cause());
} else {
return null;
}
}
@Override
public Throwable cause() {
return null;
}
@Override
public boolean succeeded() {
return AsyncResult.this.succeeded() || AsyncResult.this.failed();
}
@Override
public boolean failed() {
return false;
}
};
}
/**
* Map the failure of this async result to a specific {@code value}.
*
* When this async result fails, this {@code value} will succeeed the async result returned by this method call.
*
* When this async succeeds, the result will be propagated to the returned async result.
*
* @param value the value that eventually completes the mapped async result
* @return the mapped async result
*/
default AsyncResult otherwise(T value) {
return otherwise(err -> value);
}
/**
* Map the failure of this async result to {@code null}.
*
* This is a convenience for {@code asyncResult.otherwise((T) null)}.
*
* When this async result fails, the {@code null} will succeeed the async result returned by this method call.
*
* When this async succeeds, the result will be propagated to the returned async result.
*
* @return the mapped async result
*/
default AsyncResult otherwiseEmpty() {
return otherwise(err -> null);
}
}