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Add explanation to Async Method Invocation pattern (#1680)

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* #590 make the example more interesting and add an explanation

* #590 fix checkstyle

Co-authored-by: Subhrodip Mohanta <hello@subho.xyz>
This commit is contained in:
Ilkka Seppälä
2021-03-18 07:37:34 +02:00
committed by GitHub
parent e9106ccfc5
commit 7e91322a43
2 changed files with 159 additions and 17 deletions
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29
async-method-invocation/src/main/java/com/iluwatar/async/method/invocation/App.java
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@ -27,10 +27,12 @@ import java.util.concurrent.Callable;
import lombok.extern.slf4j.Slf4j;
/**
* 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>AsyncCallback</code> which can be provided to be executed on task completion and
* <code>AsyncExecutor</code> that manages the execution of the async tasks.
* In this example, we are launching space rockets and deploying lunar rovers.
*
* <p>The application demonstrates the async method invocation pattern. The key parts of the
* pattern are <code>AsyncResult</code> which is an intermediate container for an asynchronously
* evaluated 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.
*
* <p>The main method shows example flow of async invocations. The main thread starts multiple
* tasks with variable durations and then continues its own work. When the main thread has done it's
@ -68,13 +70,14 @@ public class App {
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("Callback result 4"));
final var asyncResult4 = executor.startProcess(lazyval(20, 400),
callback("Deploying lunar rover"));
final var asyncResult5 =
executor.startProcess(lazyval("callback", 600), callback("Callback result 5"));
executor.startProcess(lazyval("callback", 600), callback("Deploying lunar rover"));
// 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
log("Some hard work done");
Thread.sleep(350); // Oh boy, we are working hard here
log("Mission command is sipping coffee");
// wait for completion of the tasks
final var result1 = executor.endProcess(asyncResult1);
@ -84,9 +87,9 @@ public class App {
asyncResult5.await();
// log the results of the tasks, callbacks log immediately when complete
log("Result 1: " + result1);
log("Result 2: " + result2);
log("Result 3: " + result3);
log("Space rocket <" + result1 + "> launch complete");
log("Space rocket <" + result2 + "> launch complete");
log("Space rocket <" + result3 + "> launch complete");
}
/**
@ -99,7 +102,7 @@ public class App {
private static <T> Callable<T> lazyval(T value, long delayMillis) {
return () -> {
Thread.sleep(delayMillis);
log("Task completed with: " + value);
log("Space rocket <" + value + "> launched successfully");
return value;
};
}
@ -115,7 +118,7 @@ public class App {
if (ex.isPresent()) {
log(name + " failed: " + ex.map(Exception::getMessage).orElse(""));
} else {
log(name + ": " + value);
log(name + " <" + value + ">");
}
};
}