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@ -79,12 +79,12 @@ public abstract class ActiveCreature{
return this.name;
}
}
```
We can see that any class that will extend the ActiveCreature class will have its own thread of control to execute and invocate methods.
For example, the Orc class:
```java
public class Orc extends ActiveCreature {
@ -96,7 +96,6 @@ public class Orc extends ActiveCreature {
```
Now, we can create multiple creatures such as Orcs, tell them to eat and roam and they will execute it on their own thread of control:
```java
public static void main(String[] args) {
var app = new App();
@ -122,4 +121,4 @@ Now, we can create multiple creatures such as Orcs, tell them to eat and roam an
## Class diagram
![alt text](./etc/active-object.urm.PNG "Active Object class diagram")
![alt text](./etc/active-object.urm.png "Active Object class diagram")

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@ -1,26 +1,3 @@
/*
* The MIT License
* Copyright © 2014-2021 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.activeobject;
import java.util.concurrent.BlockingQueue;

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@ -1,26 +1,3 @@
/*
* The MIT License
* Copyright © 2014-2021 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.activeobject;
/**

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@ -1,26 +1,3 @@
/*
* The MIT License
* Copyright © 2014-2021 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.activeobject;
import static org.junit.jupiter.api.Assertions.assertEquals;

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@ -1,26 +1,3 @@
/*
* The MIT License
* Copyright © 2014-2021 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.activeobject;
import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;

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@ -9,160 +9,21 @@ tags:
---
## Intent
Asynchronous method invocation is a pattern where the calling thread
Asynchronous method invocation is pattern where the calling thread
is not blocked while waiting results of tasks. The pattern provides parallel
processing of multiple independent tasks and retrieving the results via
callbacks or waiting until everything is done.
## Explanation
Real world example
> Launching space rockets is an exciting business. The mission command gives an order to launch and
> after some undetermined time, the rocket either launches successfully or fails miserably.
In plain words
> Asynchronous method invocation starts task processing and returns immediately before the task is
> ready. The results of the task processing are returned to the caller later.
Wikipedia says
> In multithreaded computer programming, asynchronous method invocation (AMI), also known as
> asynchronous method calls or the asynchronous pattern is a design pattern in which the call site
> is not blocked while waiting for the called code to finish. Instead, the calling thread is
> notified when the reply arrives. Polling for a reply is an undesired option.
**Programmatic Example**
In this example, we are launching space rockets and deploying lunar rovers.
The application demonstrates the async method invocation pattern. The key parts of the pattern are
`AsyncResult` which is an intermediate container for an asynchronously evaluated value,
`AsyncCallback` which can be provided to be executed on task completion and `AsyncExecutor` that
manages the execution of the async tasks.
```java
public interface AsyncResult<T> {
boolean isCompleted();
T getValue() throws ExecutionException;
void await() throws InterruptedException;
}
```
```java
public interface AsyncCallback<T> {
void onComplete(T value, Optional<Exception> ex);
}
```
```java
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;
}
```
`ThreadAsyncExecutor` is an implementation of `AsyncExecutor`. Some of its key parts are highlighted
next.
```java
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();
}
}
```
Then we are ready to launch some rockets to see how everything works together.
```java
public static void main(String[] args) throws Exception {
// construct a new executor that will run async tasks
var executor = new ThreadAsyncExecutor();
// start few async tasks with varying processing times, two last with callback handlers
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"));
// emulate processing in the current thread while async tasks are running in their own threads
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);
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
log("Space rocket <" + result1 + "> launch complete");
log("Space rocket <" + result2 + "> launch complete");
log("Space rocket <" + result3 + "> launch complete");
}
```
Here's the program console output.
```java
21:47:08.227 [executor-2] INFO com.iluwatar.async.method.invocation.App - Space rocket <test> launched successfully
21:47:08.269 [main] INFO com.iluwatar.async.method.invocation.App - Mission command is sipping coffee
21:47:08.318 [executor-4] INFO com.iluwatar.async.method.invocation.App - Space rocket <20> launched successfully
21:47:08.335 [executor-4] INFO com.iluwatar.async.method.invocation.App - Deploying lunar rover <20>
21:47:08.414 [executor-1] INFO com.iluwatar.async.method.invocation.App - Space rocket <10> launched successfully
21:47:08.519 [executor-5] INFO com.iluwatar.async.method.invocation.App - Space rocket <callback> launched successfully
21:47:08.519 [executor-5] INFO com.iluwatar.async.method.invocation.App - Deploying lunar rover <callback>
21:47:08.616 [executor-3] INFO com.iluwatar.async.method.invocation.App - Space rocket <50> launched successfully
21:47:08.617 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <10> launch complete
21:47:08.617 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <test> launch complete
21:47:08.618 [main] INFO com.iluwatar.async.method.invocation.App - Space rocket <50> launch complete
```
# Class diagram
![alt text](./etc/async-method-invocation.png "Async Method Invocation")
## Applicability
Use the async method invocation pattern when
Use async method invocation pattern when
* You have multiple independent tasks that can run in parallel
* You need to improve the performance of a group of sequential tasks
* You have a limited amount of processing capacity or long-running tasks and the caller should not wait for the tasks to be ready
* You have limited amount of processing capacity or long running tasks and the
caller should not wait the tasks to be ready
## Real world examples

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@ -27,12 +27,10 @@ import java.util.concurrent.Callable;
import lombok.extern.slf4j.Slf4j;
/**
* 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.
* 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.
*
* <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
@ -70,14 +68,13 @@ 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("Deploying lunar rover"));
final var asyncResult4 = executor.startProcess(lazyval(20, 400), callback("Callback result 4"));
final var asyncResult5 =
executor.startProcess(lazyval("callback", 600), callback("Deploying lunar rover"));
executor.startProcess(lazyval("callback", 600), callback("Callback result 5"));
// emulate processing in the current thread while async tasks are running in their own threads
Thread.sleep(350); // Oh boy, we are working hard here
log("Mission command is sipping coffee");
Thread.sleep(350); // Oh boy I'm working hard here
log("Some hard work done");
// wait for completion of the tasks
final var result1 = executor.endProcess(asyncResult1);
@ -87,9 +84,9 @@ public class App {
asyncResult5.await();
// log the results of the tasks, callbacks log immediately when complete
log("Space rocket <" + result1 + "> launch complete");
log("Space rocket <" + result2 + "> launch complete");
log("Space rocket <" + result3 + "> launch complete");
log("Result 1: " + result1);
log("Result 2: " + result2);
log("Result 3: " + result3);
}
/**
@ -102,7 +99,7 @@ public class App {
private static <T> Callable<T> lazyval(T value, long delayMillis) {
return () -> {
Thread.sleep(delayMillis);
log("Space rocket <" + value + "> launched successfully");
log("Task completed with: " + value);
return value;
};
}
@ -118,7 +115,7 @@ public class App {
if (ex.isPresent()) {
log(name + " failed: " + ex.map(Exception::getMessage).orElse(""));
} else {
log(name + " <" + value + ">");
log(name + ": " + value);
}
};
}

View File

@ -105,7 +105,7 @@ Program output:
```java
This is Ford.
This is Ferrari.
This Ferrari.
```
## Class Diagram