gaspersic/java-design-patterns
1
0
Fork 0
Code Issues Pull Requests Projects Releases Wiki Activity

#66 Balking Pattern

Browse Source
This commit is contained in:
Katarzyna Rzepecka
2017-01-06 01:20:59 +01:00
parent 175e9f58c1
commit 1aed5905d7
10 changed files with 384 additions and 0 deletions
Download Patch File Download Diff File Expand all files Collapse all files

23
balking/README.md Normal file
View File

@@ -0,0 +1,23 @@
---
layout: pattern
title: Balking
folder: balking
permalink: /patterns/balking/
categories: Concurrency
tags:
- Java
- Difficulty-Beginner
---
## Intent
Balking Pattern is used to prevent an object from executing certain code if it is an
incomplete or inappropriate state
![alt text](./etc/balking.png "Balking")
## Applicability
Use the Balking pattern when
*you want to invoke an action on an object only when it is in a particular state
*objects are generally only in a state that is prone to balking temporarily
but for an unknown amount of time

BIN
balking/etc/balking.png Normal file
View File

Binary file not shown.
Side by Side

After

Width:  |  Height:  |  Size: 21 KiB

46
balking/etc/balking.ucls Normal file
View File

@@ -0,0 +1,46 @@
<?xml version="1.0" encoding="UTF-8"?>
<class-diagram version="1.1.13" icons="true" automaticImage="PNG" always-add-relationships="false"
generalizations="true" realizations="true" associations="true" dependencies="false" nesting-relationships="true"
router="FAN">
<class id="1" language="java" name="com.iluwatar.balking.App" project="balking"
file="/balking/src/main/java/com/iluwatar/balking/App.java" binary="false" corner="BOTTOM_RIGHT">
<position height="113" width="114" x="135" y="103"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<class id="2" language="java" name="com.iluwatar.balking.WashingMachine" project="balking"
file="/balking/src/main/java/com/iluwatar/balking/WashingMachine.java" binary="false" corner="BOTTOM_RIGHT">
<position height="149" width="268" x="289" y="103"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</class>
<enumeration id="3" language="java" name="com.iluwatar.balking.WashingMachineState" project="balking"
file="/balking/src/main/java/com/iluwatar/balking/WashingMachineState.java" binary="false" corner="BOTTOM_RIGHT">
<position height="113" width="192" x="289" y="292"/>
<display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</display>
</enumeration>
<association id="4">
<end type="SOURCE" refId="2" navigable="false">
<attribute id="5" name="washingMachineState"/>
<multiplicity id="6" minimum="0" maximum="1"/>
</end>
<end type="TARGET" refId="3" navigable="true"/>
<display labels="true" multiplicity="true"/>
</association>
<classifier-display autosize="true" stereotype="true" package="true" initial-value="false" signature="true"
sort-features="false" accessors="true" visibility="true">
<attributes public="true" package="true" protected="true" private="true" static="true"/>
<operations public="true" package="true" protected="true" private="true" static="true"/>
</classifier-display>
<association-display labels="true" multiplicity="true"/>
</class-diagram>

24
balking/etc/balking.urm.puml Normal file
View File

@@ -0,0 +1,24 @@
@startuml
package com.iluwatar.balking {
class App {
- LOGGER : Logger {static}
+ App()
+ main(args : String[]) {static}
}
class WashingMachine {
- LOGGER : Logger {static}
- washingMachineState : WashingMachineState
+ WashingMachine()
+ endOfWashing()
+ getWashingMachineState() : WashingMachineState
+ wash()
}
enum WashingMachineState {
+ ENABLED {static}
+ WASHING {static}
+ valueOf(name : String) : WashingMachineState {static}
+ values() : WashingMachineState[] {static}
}
}
WashingMachine --> "-washingMachineState" WashingMachineState
@enduml

46
balking/pom.xml Normal file
View File

@@ -0,0 +1,46 @@
<?xml version="1.0" encoding="UTF-8"?>
<!--
The MIT License
Copyright (c) 2014 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 xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<parent>
<artifactId>java-design-patterns</artifactId>
<groupId>com.iluwatar</groupId>
<version>1.14.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>balking</artifactId>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<scope>test</scope>
</dependency>
</dependencies>
</project>

53
balking/src/main/java/com/iluwatar/balking/App.java Normal file
View File

@@ -0,0 +1,53 @@
/**
* The MIT License
* Copyright (c) 2014 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.balking;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class App {
private static final Logger LOGGER = LoggerFactory.getLogger(App.class);
/**
* @param args the command line arguments - not used
*/
public static void main(String... args) {
final WashingMachine washingMachine = new WashingMachine();
ExecutorService executorService = Executors.newFixedThreadPool(3);
for (int i = 0; i < 3; i++) {
executorService.execute(washingMachine::wash);
}
executorService.shutdown();
try {
executorService.awaitTermination(10, TimeUnit.SECONDS);
} catch (InterruptedException ie) {
LOGGER.error("ERROR: Waiting on executor service shutdown!");
}
}
}

73
balking/src/main/java/com/iluwatar/balking/WashingMachine.java Normal file
View File

@@ -0,0 +1,73 @@
/**
* The MIT License
* Copyright (c) 2014 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.balking;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
public class WashingMachine {
private static final Logger LOGGER = LoggerFactory.getLogger(WashingMachine.class);
private WashingMachineState washingMachineState;
public WashingMachine() {
washingMachineState = WashingMachineState.ENABLED;
}
public WashingMachineState getWashingMachineState() {
return washingMachineState;
}
/**
* Method responsible for washing
* if the object is in appropriate state
*/
public void wash() {
synchronized (this) {
LOGGER.info("{}: Actual machine state: {}", Thread.currentThread().getName(), getWashingMachineState());
if (washingMachineState == WashingMachineState.WASHING) {
LOGGER.error("ERROR: Cannot wash if the machine has been already washing!");
return;
}
washingMachineState = WashingMachineState.WASHING;
}
LOGGER.info("{}: Doing the washing", Thread.currentThread().getName());
try {
Thread.sleep(50);
} catch (InterruptedException ie) {
ie.printStackTrace();
}
endOfWashing();
}
/**
* Method responsible of ending the washing
* by changing machine state
*/
public synchronized void endOfWashing() {
washingMachineState = WashingMachineState.ENABLED;
LOGGER.info("{}: Washing completed.", Thread.currentThread().getId());
}
}

25
balking/src/main/java/com/iluwatar/balking/WashingMachineState.java Normal file
View File

@@ -0,0 +1,25 @@
/**
* The MIT License
* Copyright (c) 2014 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.balking;
public enum WashingMachineState {ENABLED, WASHING}

32
balking/src/test/java/com/iluwatar/balking/AppTest.java Normal file
View File

@@ -0,0 +1,32 @@
/**
* The MIT License
* Copyright (c) 2014 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.balking;
public class AppTest {
@org.junit.Test
public void main() throws Exception {
String[] args = {};
App.main(args);
}
}

62
balking/src/test/java/com/iluwatar/balking/WashingMachineTest.java Normal file
View File

@@ -0,0 +1,62 @@
/**
* The MIT License
* Copyright (c) 2014 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.balking;
import org.junit.Test;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
import static org.junit.Assert.*;
public class WashingMachineTest {
private volatile WashingMachineState machineStateGlobal;
@Test
public void wash() throws Exception {
WashingMachine washingMachine = new WashingMachine();
ExecutorService executorService = Executors.newFixedThreadPool(2);
executorService.execute(washingMachine::wash);
executorService.execute(() -> {
washingMachine.wash();
machineStateGlobal = washingMachine.getWashingMachineState();
});
executorService.shutdown();
try {
executorService.awaitTermination(10, TimeUnit.SECONDS);
} catch (InterruptedException ie) {
ie.printStackTrace();
}
assertEquals(WashingMachineState.WASHING, machineStateGlobal);
}
@Test
public void endOfWashing() throws Exception {
WashingMachine washingMachine = new WashingMachine();
washingMachine.wash();
assertEquals(WashingMachineState.ENABLED, washingMachine.getWashingMachineState());
}
}