org.springframework.util.concurrent.ListenableFutureCallbackRegistry Maven / Gradle / Ivy
/*
* Copyright 2002-2018 the original author or authors.
*
* 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
*
* https://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 org.springframework.util.concurrent;
import java.util.LinkedList;
import java.util.Queue;
import org.springframework.lang.Nullable;
import org.springframework.util.Assert;
/**
* Helper class for {@link ListenableFuture} implementations that maintains a
* of success and failure callbacks and helps to notify them.
*
* Inspired by {@code com.google.common.util.concurrent.ExecutionList}.
*
* @author Arjen Poutsma
* @author Sebastien Deleuze
* @author Rossen Stoyanchev
* @since 4.0
* @param the callback result type
*/
public class ListenableFutureCallbackRegistry {
private final Queue> successCallbacks = new LinkedList<>();
private final Queue failureCallbacks = new LinkedList<>();
private State state = State.NEW;
@Nullable
private Object result;
private final Object mutex = new Object();
/**
* Add the given callback to this registry.
* @param callback the callback to add
*/
public void addCallback(ListenableFutureCallback callback) {
Assert.notNull(callback, "'callback' must not be null");
synchronized (this.mutex) {
switch (this.state) {
case NEW:
this.successCallbacks.add(callback);
this.failureCallbacks.add(callback);
break;
case SUCCESS:
notifySuccess(callback);
break;
case FAILURE:
notifyFailure(callback);
break;
}
}
}
@SuppressWarnings("unchecked")
private void notifySuccess(SuccessCallback callback) {
try {
callback.onSuccess((T) this.result);
}
catch (Throwable ex) {
// Ignore
}
}
private void notifyFailure(FailureCallback callback) {
Assert.state(this.result instanceof Throwable, "No Throwable result for failure state");
try {
callback.onFailure((Throwable) this.result);
}
catch (Throwable ex) {
// Ignore
}
}
/**
* Add the given success callback to this registry.
* @param callback the success callback to add
* @since 4.1
*/
public void addSuccessCallback(SuccessCallback callback) {
Assert.notNull(callback, "'callback' must not be null");
synchronized (this.mutex) {
switch (this.state) {
case NEW:
this.successCallbacks.add(callback);
break;
case SUCCESS:
notifySuccess(callback);
break;
}
}
}
/**
* Add the given failure callback to this registry.
* @param callback the failure callback to add
* @since 4.1
*/
public void addFailureCallback(FailureCallback callback) {
Assert.notNull(callback, "'callback' must not be null");
synchronized (this.mutex) {
switch (this.state) {
case NEW:
this.failureCallbacks.add(callback);
break;
case FAILURE:
notifyFailure(callback);
break;
}
}
}
/**
* Trigger a {@link ListenableFutureCallback#onSuccess(Object)} call on all
* added callbacks with the given result.
* @param result the result to trigger the callbacks with
*/
public void success(@Nullable T result) {
synchronized (this.mutex) {
this.state = State.SUCCESS;
this.result = result;
SuccessCallback callback;
while ((callback = this.successCallbacks.poll()) != null) {
notifySuccess(callback);
}
}
}
/**
* Trigger a {@link ListenableFutureCallback#onFailure(Throwable)} call on all
* added callbacks with the given {@code Throwable}.
* @param ex the exception to trigger the callbacks with
*/
public void failure(Throwable ex) {
synchronized (this.mutex) {
this.state = State.FAILURE;
this.result = ex;
FailureCallback callback;
while ((callback = this.failureCallbacks.poll()) != null) {
notifyFailure(callback);
}
}
}
private enum State {NEW, SUCCESS, FAILURE}
}