Reformat Async Method Invocation - Issue #224

This commit is contained in:
Ankur Kaushal 2015-11-01 17:33:25 -05:00
parent 95c16200e7
commit 16a8c85af6
6 changed files with 229 additions and 228 deletions

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@ -4,23 +4,24 @@ import java.util.concurrent.Callable;
/** /**
* This application demonstrates the async method invocation pattern. Key parts of the pattern are * This application demonstrates the async method invocation pattern. Key parts of the pattern are
* <code>AsyncResult</code> which is an intermediate container for an asynchronously evaluated value, * <code>AsyncResult</code> which is an intermediate container for an asynchronously evaluated
* <code>AsyncCallback</code> which can be provided to be executed on task completion and * value, <code>AsyncCallback</code> which can be provided to be executed on task completion and
* <code>AsyncExecutor</code> that manages the execution of the async tasks. * <code>AsyncExecutor</code> that manages the execution of the async tasks.
* <p> * <p>
* The main method shows example flow of async invocations. The main thread starts multiple tasks with * The main method shows example flow of async invocations. The main thread starts multiple tasks
* variable durations and then continues its own work. When the main thread has done it's job it collects * with variable durations and then continues its own work. When the main thread has done it's job
* the results of the async tasks. Two of the tasks are handled with callbacks, meaning the callbacks are * it collects the results of the async tasks. Two of the tasks are handled with callbacks, meaning
* executed immediately when the tasks complete. * the callbacks are executed immediately when the tasks complete.
* <p> * <p>
* Noteworthy difference of thread usage between the async results and callbacks is that the async results * Noteworthy difference of thread usage between the async results and callbacks is that the async
* are collected in the main thread but the callbacks are executed within the worker threads. This should be * results are collected in the main thread but the callbacks are executed within the worker
* noted when working with thread pools. * threads. This should be noted when working with thread pools.
* <p> * <p>
* Java provides its own implementations of async method invocation pattern. FutureTask, CompletableFuture * Java provides its own implementations of async method invocation pattern. FutureTask,
* and ExecutorService are the real world implementations of this pattern. But due to the nature of parallel * CompletableFuture and ExecutorService are the real world implementations of this pattern. But due
* programming, the implementations are not trivial. This example does not take all possible scenarios into * to the nature of parallel programming, the implementations are not trivial. This example does not
* account but rather provides a simple version that helps to understand the pattern. * take all possible scenarios into account but rather provides a simple version that helps to
* understand the pattern.
* *
* @see AsyncResult * @see AsyncResult
* @see AsyncCallback * @see AsyncCallback
@ -40,8 +41,10 @@ public class App {
AsyncResult<Integer> asyncResult1 = executor.startProcess(lazyval(10, 500)); AsyncResult<Integer> asyncResult1 = executor.startProcess(lazyval(10, 500));
AsyncResult<String> asyncResult2 = executor.startProcess(lazyval("test", 300)); AsyncResult<String> asyncResult2 = executor.startProcess(lazyval("test", 300));
AsyncResult<Long> asyncResult3 = executor.startProcess(lazyval(50L, 700)); AsyncResult<Long> asyncResult3 = executor.startProcess(lazyval(50L, 700));
AsyncResult<Integer> asyncResult4 = executor.startProcess(lazyval(20, 400), callback("Callback result 4")); AsyncResult<Integer> asyncResult4 =
AsyncResult<String> asyncResult5 = executor.startProcess(lazyval("callback", 600), callback("Callback result 5")); executor.startProcess(lazyval(20, 400), callback("Callback result 4"));
AsyncResult<String> asyncResult5 =
executor.startProcess(lazyval("callback", 600), callback("Callback result 5"));
// emulate processing in the current thread while async tasks are running in their own threads // emulate processing in the current thread while async tasks are running in their own threads
Thread.sleep(350); // Oh boy I'm working hard here Thread.sleep(350); // Oh boy I'm working hard here

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@ -18,5 +18,4 @@ public interface AsyncCallback<T> {
* @param ex empty value if execution succeeds, some exception if executions fails * @param ex empty value if execution succeeds, some exception if executions fails
*/ */
void onComplete(T value, Optional<Exception> ex); void onComplete(T value, Optional<Exception> ex);
} }

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@ -38,5 +38,4 @@ public interface AsyncExecutor {
* @throws InterruptedException if the execution is interrupted * @throws InterruptedException if the execution is interrupted
*/ */
<T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException; <T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException;
} }

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@ -34,7 +34,8 @@ public class ThreadAsyncExecutor implements AsyncExecutor {
} }
@Override @Override
public <T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException, InterruptedException { public <T> T endProcess(AsyncResult<T> asyncResult) throws ExecutionException,
InterruptedException {
if (asyncResult.isCompleted()) { if (asyncResult.isCompleted()) {
return asyncResult.getValue(); return asyncResult.getValue();
} else { } else {
@ -44,8 +45,8 @@ public class ThreadAsyncExecutor implements AsyncExecutor {
} }
/** /**
* Simple implementation of async result that allows completing it successfully with a value * Simple implementation of async result that allows completing it successfully with a value or
* or exceptionally with an exception. A really simplified version from its real life cousins * exceptionally with an exception. A really simplified version from its real life cousins
* FutureTask and CompletableFuture. * FutureTask and CompletableFuture.
* *
* @see java.util.concurrent.FutureTask * @see java.util.concurrent.FutureTask
@ -70,8 +71,8 @@ public class ThreadAsyncExecutor implements AsyncExecutor {
} }
/** /**
* Sets the value from successful execution and executes callback if available. Notifies * Sets the value from successful execution and executes callback if available. Notifies any
* any thread waiting for completion. * thread waiting for completion.
* *
* @param value value of the evaluated task * @param value value of the evaluated task
*/ */
@ -85,8 +86,8 @@ public class ThreadAsyncExecutor implements AsyncExecutor {
} }
/** /**
* Sets the exception from failed execution and executes callback if available. Notifies * Sets the exception from failed execution and executes callback if available. Notifies any
* any thread waiting for completion. * thread waiting for completion.
* *
* @param exception exception of the failed task * @param exception exception of the failed task
*/ */

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@ -14,5 +14,4 @@ public class AppTest {
String[] args = {}; String[] args = {};
App.main(args); App.main(args);
} }
} }