标签：java asynchronous event-handling multithreading priority-queue
我的目标是按顺序发布异步事件,这些事件也按顺序到达并花费任意时间进行处理.所以下面是我目前的实现只使用wait和notify. MyThread处理事件,通过id将结果放入哈希表中,如果在按顺序发布此事件之前被阻塞,则通知Scheduler线程.
使用java.util.concurrent包实现此功能会有什么更好,更简洁的方法？
import java.util.Map;
import java.util.Random;
import java.util.concurrent.ConcurrentHashMap;
public class AsyncHandler {
private final Map<Integer, Object> locks = new ConcurrentHashMap<Integer, Object>();
private final Map<Integer, Result> results = new ConcurrentHashMap<Integer, Result>();
private static final Random rand = new Random();
public AsyncHandler () {
new Scheduler(this, locks, results).start();
}
public void handleEvent(Event event) {
System.out.println("handleEvent(" + event.id + ")");
new MyThread(this, event, locks, results).start();
}
public Result processEvent (Event event) {
System.out.println("processEvent(" + event.id + ")");
locks.put(event.id, new Object());
try {
Thread.sleep(rand.nextInt(10000));
} catch (InterruptedException e) {
System.out.println(e);
}
return new Result(event.id);
}
public void postProcessEvent (Result result) {
System.out.println(result.id);
}
public static void main (String[] args) {
AsyncHandler async = new AsyncHandler();
for (int i = 0; i < 100; i++) {
async.handleEvent(new Event(i));
}
}
}
class Event {
int id;
public Event (int id) {
this.id = id;
}
}
class Result {
int id;
public Result (int id) {
this.id = id;
}
}
class MyThread extends Thread {
private final Event event;
private final Map<Integer, Object> locks;
private final Map<Integer, Result> results;
private final AsyncHandler async;
public MyThread (AsyncHandler async, Event event, Map<Integer, Object> locks, Map<Integer, Result> results) {
this.async = async;
this.event = event;
this.locks = locks;
this.results = results;
}
@Override
public void run () {
Result res = async.processEvent(event);
results.put(event.id, res);
Object lock = locks.get(event.id);
synchronized (lock) {
lock.notifyAll();
}
}
}
class Scheduler extends Thread {
private int curId = 0;
private final AsyncHandler async;
private final Map<Integer, Object> locks;
private final Map<Integer, Result> results;
public Scheduler (AsyncHandler async, Map<Integer, Object> locks, Map<Integer, Result> results) {
this.async = async;
this.locks = locks;
this.results = results;
}
@Override
public void run () {
while (true) {
Result res = results.get(curId);
if (res == null) {
Object lock = locks.get(curId);
//TODO: eliminate busy waiting
if (lock == null) {
continue;
}
synchronized (lock) {
try {
lock.wait();
} catch (InterruptedException e) {
System.out.println(e);
System.exit(1);
}
}
res = results.get(curId);
}
async.postProcessEvent(res);
results.remove(curId);
locks.remove(curId);
curId++;
}
}
}
解决方法:
是的并发库会简单得多.
ExecutorService旨在包装线程池和队列,以便为每个任务返回Future,并提供等待结果的任何线程.
如果您想按顺序处理结果,请按顺序处理未来结果的线程.
按顺序处理异步结果
public class Main {
public static void main(String[] args) {
Main main = new Main();
for (int i = 0; i < 1000; i++) {
final int finalI = i;
main.submitTask(new Callable<Long>() {
@Override
public Long call() throws Exception {
long millis = (long) (Math.pow(2000, Math.random()));
Thread.sleep(millis);
return millis;
}
}, new ResultHandler<Long>() {
@Override
public void onFuture(Future<Long> future) throws ExecutionException, InterruptedException {
System.out.println(new Date() + ": " + finalI + " - Slept for " + future.get() + " millis");
}
});
}
main.shutdown();
}
public interface ResultHandler<T> {
void onFuture(Future<T> future) throws Exception;
}
private final ExecutorService pool = Executors.newFixedThreadPool(10);
private final ExecutorService result = Executors.newSingleThreadExecutor();
public synchronized <T> void submitTask(Callable<T> callable, final ResultHandler<T> resultHandler) {
final Future<T> future = pool.submit(callable);
result.submit(new Runnable() {
@Override
public void run() {
try {
resultHandler.onFuture(future);
} catch (Exception e) {
e.printStackTrace();
}
}
});
}
public void shutdown() {
pool.shutdown();
result.shutdown();
}
}
版画
Wed Oct 02 16:32:07 CEST 2013: 0 - Slept for 1 millis
Wed Oct 02 16:32:07 CEST 2013: 1 - Slept for 1899 millis
Wed Oct 02 16:32:09 CEST 2013: 2 - Slept for 32 millis
Wed Oct 02 16:32:09 CEST 2013: 3 - Slept for 32 millis
Wed Oct 02 16:32:09 CEST 2013: 4 - Slept for 214 millis
Wed Oct 02 16:32:09 CEST 2013: 5 - Slept for 366 millis
... many deleted ...
Wed Oct 02 16:32:09 CEST 2013: 82 - Slept for 6 millis
Wed Oct 02 16:32:09 CEST 2013: 83 - Slept for 1636 millis
Wed Oct 02 16:32:10 CEST 2013: 84 - Slept for 44 millis
Wed Oct 02 16:32:10 CEST 2013: 85 - Slept for 1 millis
您可以看到,虽然某些任务比其他任务花费的时间长,但输出的顺序是添加任务的顺序.您还可以看到它在同一秒内处理许多任务(同时)
标签：java,asynchronous,event-handling,multithreading,priority-queue 来源： https://codeday.me/bug/20190624/1282079.html
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