【设计模式】JAVA Design Patterns——Async Method Invocation（异步方法调用模式）

public interface AsyncResult<T> {
  boolean isCompleted();
  T getValue() throws ExecutionException;
  void await() throws InterruptedException;
}

public interface AsyncCallback<T> {
  void onComplete(T value, Optional<Exception> ex);
}

public interface AsyncExecutor {
  <T> AsyncResult<T> startProcess(Callable<T> task);
  <T> AsyncResult<T> startProcess(Callable<T> task, AsyncCallback<T> callback);
  <T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException;
}

public class ThreadAsyncExecutor implements AsyncExecutor {
 
  @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) {
    var 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();
  }
}

public static void main(String[] args) throws Exception {
  // 构造一个将执行异步任务的新执行程序
  var executor = new ThreadAsyncExecutor();
 
  // 以不同的处理时间开始一些异步任务，最后两个使用回调处理程序
  final var asyncResult1 = executor.startProcess(lazyval(10, 500));
  final var asyncResult2 = executor.startProcess(lazyval("test", 300));
  final var asyncResult3 = executor.startProcess(lazyval(50L, 700));
  final var asyncResult4 = executor.startProcess(lazyval(20, 400), callback("Deploying lunar rover"));
  final var asyncResult5 =
      executor.startProcess(lazyval("callback", 600), callback("Deploying lunar rover"));
 
  // 在当前线程中模拟异步任务正在它们自己的线程中执行
  Thread.sleep(350); // 哦，兄弟，我们在这很辛苦
  log("Mission command is sipping coffee");
 
  // 等待任务完成
  final var result1 = executor.endProcess(asyncResult1);
  final var result2 = executor.endProcess(asyncResult2);
  final var result3 = executor.endProcess(asyncResult3);
  asyncResult4.await();
  asyncResult5.await();
 
  // log the results of the tasks, callbacks log immediately when complete
  // 记录任务结果的日志， 回调的日志会在回调完成时立刻记录
  log("Space rocket <" + result1 + "> launch complete");
  log("Space rocket <" + result2 + "> launch complete");
  log("Space rocket <" + result3 + "> launch complete");
}

14:32:01.227 [executor-2] INFO com.iluwatar.async.method.invocation.App - Space rocket <test> launched successfully
14:32:01.269 [main] INFO com.iluwatar.async.method.invocation.App - Mission command is sipping coffee
14:32:01.318 [executor-4] INFO com.iluwatar.async.method.invocation.App - Space rocket <20> launched successfully
14:32:01.335 [executor-4] INFO com.iluwatar.async.method.invocation.App - Deploying lunar rover <20>
14:32:01.414 [executor-1] INFO com.iluwatar.async.method.invocation.App - Space rocket <10> launched successfully
14:32:01.519 [executor-5] INFO com.iluwatar.async.method.invocation.App - Space rocket <callback> launched successfully
14:32:01.519 [executor-5] INFO com.iluwatar.async.method.invocation.App - Deploying lunar rover <callback>
14:32:01.616 [executor-3] INFO com.iluwatar.async.method.invocation.App - Space rocket <50> launched successfully
14:32:01.617 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <10> launch complete
14:32:01.617 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <test> launch complete
14:32:01.618 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <50> launch complete