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2 Commits
async-meth
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all-contri
| Author | SHA1 | Date | |
|---|---|---|---|
| 3a56a667a7 | |||
| 524f38f23c |
@ -1422,15 +1422,6 @@
|
||||
"contributions": [
|
||||
"code"
|
||||
]
|
||||
},
|
||||
{
|
||||
"login": "noamgrinch",
|
||||
"name": "Noam Greenshtain",
|
||||
"avatar_url": "https://avatars.githubusercontent.com/u/31648669?v=4",
|
||||
"profile": "https://github.com/noamgrinch",
|
||||
"contributions": [
|
||||
"code"
|
||||
]
|
||||
}
|
||||
],
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||||
"contributorsPerLine": 4,
|
||||
|
||||
@ -10,7 +10,7 @@
|
||||
[](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns)
|
||||
[](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
|
||||
<!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
|
||||
[](#contributors-)
|
||||
[](#contributors-)
|
||||
<!-- ALL-CONTRIBUTORS-BADGE:END -->
|
||||
|
||||
<br/>
|
||||
@ -309,9 +309,6 @@ This project is licensed under the terms of the MIT license.
|
||||
<td align="center"><a href="https://github.com/richardmr36"><img src="https://avatars.githubusercontent.com/u/19147333?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Martel Richard</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=richardmr36" title="Code">💻</a></td>
|
||||
<td align="center"><a href="https://github.com/va1m"><img src="https://avatars.githubusercontent.com/u/17025445?v=4?s=100" width="100px;" alt=""/><br /><sub><b>va1m</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=va1m" title="Code">💻</a></td>
|
||||
</tr>
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||||
<tr>
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||||
<td align="center"><a href="https://github.com/noamgrinch"><img src="https://avatars.githubusercontent.com/u/31648669?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Noam Greenshtain</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=noamgrinch" title="Code">💻</a></td>
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||||
</tr>
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||||
</table>
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||||
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||||
<!-- markdownlint-restore -->
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||||
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@ -28,16 +28,20 @@ import org.junit.jupiter.api.Test;
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import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
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/**
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||||
* Issue: Add at least one assertion to this test case.
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*
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||||
* Solution: Inserted assertion to check whether the execution of the main method in {@link App}
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* throws an exception.
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* Tests that Abstract Factory example runs without errors.
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*/
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class AppTest {
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||||
|
||||
|
||||
/**
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||||
* Issue: Add at least one assertion to this test case.
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||||
*
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||||
* Solution: Inserted assertion to check whether the execution of the main method in {@link App}
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||||
* throws an exception.
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*/
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||||
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@Test
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void shouldExecuteApplicationWithoutException() {
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assertDoesNotThrow(() -> App.main(new String[]{}));
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assertDoesNotThrow(() -> App.main(new String[]{}));
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}
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}
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@ -1,125 +0,0 @@
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---
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layout: pattern
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title: Active Object
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folder: active-object
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permalink: /patterns/active-object/
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categories: Concurrency
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tags:
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- Performance
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---
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## Intent
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The active object design pattern decouples method execution from method invocation for objects that each reside in their thread of control. The goal is to introduce concurrency, by using asynchronous method invocation and a scheduler for handling requests.
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## Explanation
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The class that implements the active object pattern will contain a self-synchronization mechanism without using 'synchronized' methods.
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Real-world example
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>The Orcs are known for their wildness and untameable soul. It seems like they have their own thread of control based on previous behavior.
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To implement a creature that has its own thread of control mechanism and expose its API only and not the execution itself, we can use the Active Object pattern.
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**Programmatic Example**
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```java
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public abstract class ActiveCreature{
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private final Logger logger = LoggerFactory.getLogger(ActiveCreature.class.getName());
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private BlockingQueue<Runnable> requests;
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private String name;
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private Thread thread;
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public ActiveCreature(String name) {
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this.name = name;
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this.requests = new LinkedBlockingQueue<Runnable>();
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thread = new Thread(new Runnable() {
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@Override
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public void run() {
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while (true) {
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try {
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requests.take().run();
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} catch (InterruptedException e) {
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logger.error(e.getMessage());
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}
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}
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}
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}
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);
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thread.start();
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}
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public void eat() throws InterruptedException {
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requests.put(new Runnable() {
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@Override
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public void run() {
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logger.info("{} is eating!",name());
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logger.info("{} has finished eating!",name());
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}
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}
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);
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}
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public void roam() throws InterruptedException {
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requests.put(new Runnable() {
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@Override
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public void run() {
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logger.info("{} has started to roam and the wastelands.",name());
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}
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}
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);
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}
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public String name() {
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return this.name;
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}
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}
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```
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We can see that any class that will extend the ActiveCreature class will have its own thread of control to execute and invocate methods.
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For example, the Orc class:
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```java
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public class Orc extends ActiveCreature {
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public Orc(String name) {
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super(name);
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}
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}
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```
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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:
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```java
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public static void main(String[] args) {
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var app = new App();
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app.run();
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}
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@Override
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public void run() {
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ActiveCreature creature;
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try {
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for (int i = 0;i < creatures;i++) {
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creature = new Orc(Orc.class.getSimpleName().toString() + i);
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creature.eat();
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creature.roam();
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}
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Thread.sleep(1000);
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} catch (InterruptedException e) {
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logger.error(e.getMessage());
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}
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Runtime.getRuntime().exit(1);
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}
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```
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## Class diagram
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Binary file not shown.
|
Before Width: | Height: | Size: 19 KiB |
@ -1,25 +0,0 @@
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||||
@startuml
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package com.iluwatar.activeobject {
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abstract class ActiveCreature {
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- logger : Logger
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- name : String
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- requests : BlockingQueue<Runnable>
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- thread : Thread
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+ ActiveCreature(name : String)
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+ eat()
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+ name() : String
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+ roam()
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}
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class App {
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- creatures : Integer
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- logger : Logger
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+ App()
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+ main(args : String[]) {static}
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+ run()
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}
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class Orc {
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+ Orc(name : String)
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}
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}
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Orc --|> ActiveCreature
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@enduml
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@ -1,65 +0,0 @@
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<?xml version="1.0"?>
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<!--
|
||||
|
||||
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.
|
||||
|
||||
-->
|
||||
<project
|
||||
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
|
||||
xmlns="http://maven.apache.org/POM/4.0.0"
|
||||
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
|
||||
<modelVersion>4.0.0</modelVersion>
|
||||
<parent>
|
||||
<groupId>com.iluwatar</groupId>
|
||||
<artifactId>java-design-patterns</artifactId>
|
||||
<version>1.24.0-SNAPSHOT</version>
|
||||
</parent>
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<artifactId>active-object</artifactId>
|
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<dependencies>
|
||||
<dependency>
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||||
<groupId>org.junit.jupiter</groupId>
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<artifactId>junit-jupiter-engine</artifactId>
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||||
<scope>test</scope>
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</dependency>
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||||
</dependencies>
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<build>
|
||||
<plugins>
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||||
<!-- Maven assembly plugin is invoked with default setting which we have
|
||||
in parent pom and specifying the class having main method -->
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||||
<plugin>
|
||||
<groupId>org.apache.maven.plugins</groupId>
|
||||
<artifactId>maven-assembly-plugin</artifactId>
|
||||
<executions>
|
||||
<execution>
|
||||
<configuration>
|
||||
<archive>
|
||||
<manifest>
|
||||
<mainClass>com.iluwatar.activeobject.App</mainClass>
|
||||
</manifest>
|
||||
</archive>
|
||||
</configuration>
|
||||
</execution>
|
||||
</executions>
|
||||
</plugin>
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||||
</plugins>
|
||||
</build>
|
||||
</project>
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||||
@ -1,118 +0,0 @@
|
||||
/*
|
||||
* 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;
|
||||
import java.util.concurrent.LinkedBlockingQueue;
|
||||
|
||||
import org.slf4j.Logger;
|
||||
import org.slf4j.LoggerFactory;
|
||||
|
||||
/**
|
||||
* ActiveCreature class is the base of the active object example.
|
||||
* @author Noam Greenshtain
|
||||
*
|
||||
*/
|
||||
public abstract class ActiveCreature {
|
||||
|
||||
private static final Logger logger = LoggerFactory.getLogger(ActiveCreature.class.getName());
|
||||
|
||||
private BlockingQueue<Runnable> requests;
|
||||
|
||||
private String name;
|
||||
|
||||
private Thread thread; // Thread of execution.
|
||||
|
||||
private int status; // status of the thread of execution.
|
||||
|
||||
/**
|
||||
* Constructor and initialization.
|
||||
*/
|
||||
protected ActiveCreature(String name) {
|
||||
this.name = name;
|
||||
this.status = 0;
|
||||
this.requests = new LinkedBlockingQueue<>();
|
||||
thread = new Thread(() -> {
|
||||
boolean infinite = true;
|
||||
while (infinite) {
|
||||
try {
|
||||
requests.take().run();
|
||||
} catch (InterruptedException e) {
|
||||
if (this.status != 0) {
|
||||
logger.error("Thread was interrupted. --> {}", e.getMessage());
|
||||
}
|
||||
infinite = false;
|
||||
Thread.currentThread().interrupt();
|
||||
}
|
||||
}
|
||||
});
|
||||
thread.start();
|
||||
}
|
||||
|
||||
/**
|
||||
* Eats the porridge.
|
||||
* @throws InterruptedException due to firing a new Runnable.
|
||||
*/
|
||||
public void eat() throws InterruptedException {
|
||||
requests.put(() -> {
|
||||
logger.info("{} is eating!",name());
|
||||
logger.info("{} has finished eating!",name());
|
||||
});
|
||||
}
|
||||
|
||||
/**
|
||||
* Roam in the wastelands.
|
||||
* @throws InterruptedException due to firing a new Runnable.
|
||||
*/
|
||||
public void roam() throws InterruptedException {
|
||||
requests.put(() ->
|
||||
logger.info("{} has started to roam in the wastelands.",name())
|
||||
);
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the name of the creature.
|
||||
* @return the name of the creature.
|
||||
*/
|
||||
public String name() {
|
||||
return this.name;
|
||||
}
|
||||
|
||||
/**
|
||||
* Kills the thread of execution.
|
||||
* @param status of the thread of execution. 0 == OK, the rest is logging an error.
|
||||
*/
|
||||
public void kill(int status) {
|
||||
this.status = status;
|
||||
this.thread.interrupt();
|
||||
}
|
||||
|
||||
/**
|
||||
* Returns the status of the thread of execution.
|
||||
* @return the status of the thread of execution.
|
||||
*/
|
||||
public int getStatus() {
|
||||
return this.status;
|
||||
}
|
||||
}
|
||||
@ -1,75 +0,0 @@
|
||||
/*
|
||||
* 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.ArrayList;
|
||||
import java.util.List;
|
||||
|
||||
import org.slf4j.Logger;
|
||||
import org.slf4j.LoggerFactory;
|
||||
|
||||
/**
|
||||
* The Active Object pattern helps to solve synchronization difficulties without using
|
||||
* 'synchronized' methods. The active object will contain a thread-safe data structure
|
||||
* (such as BlockingQueue) and use to synchronize method calls by moving the logic of the method
|
||||
* into an invocator(usually a Runnable) and store it in the DSA.
|
||||
*
|
||||
* <p>In this example, we fire 20 threads to modify a value in the target class.
|
||||
*/
|
||||
public class App implements Runnable {
|
||||
|
||||
private static final Logger logger = LoggerFactory.getLogger(App.class.getName());
|
||||
|
||||
private static final int NUM_CREATURES = 3;
|
||||
|
||||
/**
|
||||
* Program entry point.
|
||||
*
|
||||
* @param args command line arguments.
|
||||
*/
|
||||
public static void main(String[] args) {
|
||||
var app = new App();
|
||||
app.run();
|
||||
}
|
||||
|
||||
@Override
|
||||
public void run() {
|
||||
List<ActiveCreature> creatures = new ArrayList<>();
|
||||
try {
|
||||
for (int i = 0;i < NUM_CREATURES;i++) {
|
||||
creatures.add(new Orc(Orc.class.getSimpleName() + i));
|
||||
creatures.get(i).eat();
|
||||
creatures.get(i).roam();
|
||||
}
|
||||
Thread.sleep(1000);
|
||||
} catch (InterruptedException e) {
|
||||
logger.error(e.getMessage());
|
||||
Thread.currentThread().interrupt();
|
||||
} finally {
|
||||
for (int i = 0;i < NUM_CREATURES;i++) {
|
||||
creatures.get(i).kill(0);
|
||||
}
|
||||
}
|
||||
}
|
||||
}
|
||||
@ -1,37 +0,0 @@
|
||||
/*
|
||||
* 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;
|
||||
|
||||
/**
|
||||
* An implementation of the ActiveCreature class.
|
||||
* @author Noam Greenshtain
|
||||
*
|
||||
*/
|
||||
public class Orc extends ActiveCreature {
|
||||
|
||||
public Orc(String name) {
|
||||
super(name);
|
||||
}
|
||||
|
||||
}
|
||||
@ -1,42 +0,0 @@
|
||||
/*
|
||||
* 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;
|
||||
|
||||
import org.junit.jupiter.api.Test;
|
||||
class ActiveCreatureTest {
|
||||
|
||||
@Test
|
||||
void executionTest() throws InterruptedException {
|
||||
ActiveCreature orc = new Orc("orc1");
|
||||
assertEquals("orc1",orc.name());
|
||||
assertEquals(0,orc.getStatus());
|
||||
orc.eat();
|
||||
orc.roam();
|
||||
orc.kill(0);
|
||||
}
|
||||
|
||||
|
||||
}
|
||||
@ -1,37 +0,0 @@
|
||||
/*
|
||||
* 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;
|
||||
|
||||
import org.junit.jupiter.api.Test;
|
||||
|
||||
|
||||
class AppTest {
|
||||
|
||||
@Test
|
||||
void shouldExecuteApplicationWithoutException() {
|
||||
assertDoesNotThrow(() -> App.main(new String[]{}));
|
||||
}
|
||||
}
|
||||
@ -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
|
||||
|
||||
|
||||
|
||||
## 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
|
||||
|
||||
|
||||
@ -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);
|
||||
}
|
||||
};
|
||||
}
|
||||
|
||||
@ -105,7 +105,7 @@ Program output:
|
||||
|
||||
```java
|
||||
This is Ford.
|
||||
This is Ferrari.
|
||||
This Ferrari.
|
||||
```
|
||||
|
||||
## Class Diagram
|
||||
|
||||
Reference in New Issue
Block a user