/**
* The MIT License
* Copyright (c) 2014-2016 Ilkka Seppälä
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
package com.iluwatar.async.method.invocation;
import java.util.Optional;
import java.util.concurrent.Callable;
import java.util.concurrent.ExecutionException;
import java.util.concurrent.atomic.AtomicInteger;
/**
*
* Implementation of async executor that creates a new thread for every task.
*
*/
public class ThreadAsyncExecutor implements AsyncExecutor {
/** Index for thread naming */
private final AtomicInteger idx = new AtomicInteger(0);
@Override
public <T> AsyncResult<T> startProcess(Callable<T> task) {
return startProcess(task, null);
}
@Override
public <T> AsyncResult<T> startProcess(Callable<T> task, AsyncCallback<T> callback) {
CompletableResult<T> result = new CompletableResult<>(callback);
new Thread(() -> {
try {
result.setValue(task.call());
} catch (Exception ex) {
result.setException(ex);
}
} , "executor-" + idx.incrementAndGet()).start();
return result;
}
@Override
public <T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException {
if (!asyncResult.isCompleted()) {
asyncResult.await();
}
return asyncResult.getValue();
}
/**
* Simple implementation of async result that allows completing it successfully with a value or exceptionally with an
* exception. A really simplified version from its real life cousins FutureTask and CompletableFuture.
*
* @see java.util.concurrent.FutureTask
* @see java.util.concurrent.CompletableFuture
*/
private static class CompletableResult<T> implements AsyncResult<T> {
static final int RUNNING = 1;
static final int FAILED = 2;
static final int COMPLETED = 3;
final Object lock;
final Optional<AsyncCallback<T>> callback;
volatile int state = RUNNING;
T value;
Exception exception;
CompletableResult(AsyncCallback<T> callback) {
this.lock = new Object();
this.callback = Optional.ofNullable(callback);
}
/**
* Sets the value from successful execution and executes callback if available. Notifies any thread waiting for
* completion.
*
* @param value
* value of the evaluated task
*/
void setValue(T value) {
this.value = value;
this.state = COMPLETED;
this.callback.ifPresent(ac -> ac.onComplete(value, Optional.<Exception>empty()));
synchronized (lock) {
lock.notifyAll();
}
}
/**
* Sets the exception from failed execution and executes callback if available. Notifies any thread waiting for
* completion.
*
* @param exception
* exception of the failed task
*/
void setException(Exception exception) {
this.exception = exception;
this.state = FAILED;
this.callback.ifPresent(ac -> ac.onComplete(null, Optional.of(exception)));
synchronized (lock) {
lock.notifyAll();
}
}
@Override
public boolean isCompleted() {
return state > RUNNING;
}
@Override
public T getValue() throws ExecutionException {
if (state == COMPLETED) {
return value;
} else if (state == FAILED) {
throw new ExecutionException(exception);
} else {
throw new IllegalStateException("Execution not completed yet");
}
}
@Override
public void await() throws InterruptedException {
synchronized (lock) {
if (!isCompleted()) {
lock.wait();
}
}
}
}
}