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

Merge pull request #1 from iluwatar/master

Browse Source 
Fork Update
This commit is contained in:
Toxic Dreamz 2020-08-19 23:26:19 +04:00 committed by GitHub
commit 60d87789a6
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
8 changed files with 149 additions and 31 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

29
.all-contributorsrc
View File

@ -1111,6 +1111,35 @@
"contributions": [
"code"
]
},
{
"login": "xdvrx1",
"name": "xdvrx1",
"avatar_url": "https://avatars0.githubusercontent.com/u/47092464?v=4",
"profile": "https://xdvrx1.github.io/",
"contributions": [
"review",
"ideas"
]
},
{
"login": "ohbus",
"name": "Subhrodip Mohanta",
"avatar_url": "https://avatars0.githubusercontent.com/u/13291222?v=4",
"profile": "http://subho.xyz",
"contributions": [
"code",
"review"
]
},
{
"login": "nahteb",
"name": "Bethan Palmer",
"avatar_url": "https://avatars3.githubusercontent.com/u/13121570?v=4",
"profile": "https://github.com/nahteb",
"contributions": [
"code"
]
}
],
"contributorsPerLine": 4,

10
.github/workflows/maven.yml → .github/workflows/maven-ci.yml vendored
View File

@ -24,13 +24,11 @@
# This workflow will build a Java project with Maven
# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-maven
name: Java CI with Maven
name: Java CI
on:
push:
branches: [ master ]
pull_request:
branches: [ master ]
jobs:
build:
@ -43,6 +41,12 @@ jobs:
uses: actions/setup-java@v1
with:
java-version: 11
- uses: actions/cache@v2
with:
path: ~/.m2/repository
key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
restore-keys: |
${{ runner.os }}-maven-
# Some tests need screen access
- name: Install xvfb
run: sudo apt-get install xvfb

57
.github/workflows/maven-pr-builder.yml vendored Normal file
View File

@ -0,0 +1,57 @@
#
# The MIT License
# Copyright © 2014-2019 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.
#
# This workflow will build a Java project with Maven
# For more information see: https://help.github.com/actions/language-and-framework-guides/building-and-testing-java-with-maven
name: Java PR Builder
on:
pull_request:
branches: [ master ]
jobs:
build:
runs-on: ubuntu-18.04
steps:
- uses: actions/checkout@v2
- name: Set up JDK 11
uses: actions/setup-java@v1
with:
java-version: 11
- uses: actions/cache@v2
with:
path: ~/.m2/repository
key: ${{ runner.os }}-maven-${{ hashFiles('**/pom.xml') }}
restore-keys: |
${{ runner.os }}-maven-
# Some tests need screen access
- name: Install xvfb
run: sudo apt-get install xvfb
# SonarQube scan does not work for forked repositories
# See https://jira.sonarsource.com/browse/MMF-1371
- name: Build with Maven
if: github.ref != 'refs/heads/master'
run: xvfb-run mvn clean verify

7
README.md
View File

@ -9,7 +9,7 @@
[![Join the chat at https://gitter.im/iluwatar/java-design-patterns](https://badges.gitter.im/Join%20Chat.svg)](https://gitter.im/iluwatar/java-design-patterns?utm_source=badge&utm_medium=badge&utm_campaign=pr-badge&utm_content=badge)
[![Sonarcloud Status](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=alert_status)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns)
<!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
[![All Contributors](https://img.shields.io/badge/all_contributors-122-orange.svg?style=flat-square)](#contributors-)
[![All Contributors](https://img.shields.io/badge/all_contributors-125-orange.svg?style=flat-square)](#contributors-)
<!-- ALL-CONTRIBUTORS-BADGE:END -->
# Introduction
@ -251,6 +251,11 @@ This project is licensed under the terms of the MIT license.
<tr>
<td align="center"><a href="https://www.linkedin.com/in/ashish-trivedi-218379135/"><img src="https://avatars3.githubusercontent.com/u/23194128?v=4" width="100px;" alt=""/><br /><sub><b>Ashish Trivedi</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ashishtrivedi16" title="Code">💻</a></td>
<td align="center"><a href="https://rayyounghong.com"><img src="https://avatars1.githubusercontent.com/u/41055099?v=4" width="100px;" alt=""/><br /><sub><b>洪月阳</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=RayYH" title="Code">💻</a></td>
<td align="center"><a href="https://xdvrx1.github.io/"><img src="https://avatars0.githubusercontent.com/u/47092464?v=4" width="100px;" alt=""/><br /><sub><b>xdvrx1</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Axdvrx1" title="Reviewed Pull Requests">👀</a> <a href="#ideas-xdvrx1" title="Ideas, Planning, & Feedback">🤔</a></td>
<td align="center"><a href="http://subho.xyz"><img src="https://avatars0.githubusercontent.com/u/13291222?v=4" width="100px;" alt=""/><br /><sub><b>Subhrodip Mohanta</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=ohbus" title="Code">💻</a> <a href="https://github.com/iluwatar/java-design-patterns/pulls?q=is%3Apr+reviewed-by%3Aohbus" title="Reviewed Pull Requests">👀</a></td>
</tr>
<tr>
<td align="center"><a href="https://github.com/nahteb"><img src="https://avatars3.githubusercontent.com/u/13121570?v=4" width="100px;" alt=""/><br /><sub><b>Bethan Palmer</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=nahteb" title="Code">💻</a></td>
</tr>
</table>

2
observer/README.md
View File

@ -46,7 +46,7 @@ public class Orcs implements WeatherObserver {
@Override
public void update(WeatherType currentWeather) {
LOGGER.info("The hobbits are facing " + currentWeather.getDescription() + " weather now");
LOGGER.info("The orcs are facing " + currentWeather.getDescription() + " weather now");
}
}

2
pom.xml
View File

@ -53,7 +53,7 @@
<jaxb-impl.version>2.3.2</jaxb-impl.version>
<annotation-api.version>1.3.2</annotation-api.version>
<system-rules.version>1.19.0</system-rules.version>
<urm.version>1.4.8</urm.version>
<urm.version>2.0.0</urm.version>
<!-- SonarCloud -->
<sonar.host.url>https://sonarcloud.io</sonar.host.url>
<sonar.organization>iluwatar</sonar.organization>

25
unit-of-work/README.md
View File

@ -11,21 +11,27 @@ tags:
---
## Intent
When a business transaction is completed, all the the updates are sent as one big unit of work to be persisted
in one go to minimize database round-trips.
When a business transaction is completed, all the the updates are sent as one big unit of work to be
persisted in one go to minimize database round-trips.
## Explanation
Real world example
> We have a database containing student information. Administrators all over the country are constantly updating this information and it causes high load on the database server. To make the load more manageable we apply to Unit of Work pattern to send many small updates in batches.
> We have a database containing student information. Administrators all over the country are
> constantly updating this information and it causes high load on the database server. To make the
> load more manageable we apply to Unit of Work pattern to send many small updates in batches.
In plain words
> Unit of Work merges many small database updates in single batch to optimize the number of round-trips.
> Unit of Work merges many small database updates in single batch to optimize the number of
> round-trips.
[MartinFowler.com](https://martinfowler.com/eaaCatalog/unitOfWork.html) says
> Maintains a list of objects affected by a business transaction and coordinates the writing out of changes and the resolution of concurrency problems.
> Maintains a list of objects affected by a business transaction and coordinates the writing out of
> changes and the resolution of concurrency problems.
**Programmatic Example**
@ -57,8 +63,9 @@ public class Student {
}
```
The essence of the implementation is the `StudentRepository` implementing the Unit of Work pattern. It maintains a map
of database operations (`context`) that need to be done and when `commit` is called it applies them in single batch.
The essence of the implementation is the `StudentRepository` implementing the Unit of Work pattern.
It maintains a map of database operations (`context`) that need to be done and when `commit` is
called it applies them in single batch.
```java
public interface IUnitOfWork<T> {
@ -160,7 +167,7 @@ public class StudentRepository implements IUnitOfWork<Student> {
}
```
Finally here's how we use the `StudentRepository` and `commit` the transaction.
Finally, here's how we use the `StudentRepository` and `commit` the transaction.
```java
studentRepository.registerNew(ram);
@ -170,9 +177,11 @@ Finally here's how we use the `StudentRepository` and `commit` the transaction.
```
## Class diagram
![alt text](etc/unit-of-work.urm.png "unit-of-work")
## Applicability
Use the Unit Of Work pattern when
* To optimize the time taken for database transactions.

48
visitor/README.md
View File

@ -9,13 +9,17 @@ tags:
---
## Intent
Represent an operation to be performed on the elements of an object structure. Visitor lets you define a new operation without changing the classes of the elements on which it operates.
Represent an operation to be performed on the elements of an object structure. Visitor lets you
define a new operation without changing the classes of the elements on which it operates.
## Explanation
Real world example
> Consider a tree structure with army units. Commander has two sergeants under it and each sergeant has three soldiers under them. Given that the hierarchy implements the visitor pattern, we can easily create new objects that interact with the commander, sergeants, soldiers or all of them.
> Consider a tree structure with army units. Commander has two sergeants under it and each sergeant
> has three soldiers under them. Given that the hierarchy implements the visitor pattern, we can
> easily create new objects that interact with the commander, sergeants, soldiers or all of them.
In plain words
@ -23,7 +27,10 @@ In plain words
Wikipedia says
> In object-oriented programming and software engineering, the visitor design pattern is a way of separating an algorithm from an object structure on which it operates. A practical result of this separation is the ability to add new operations to existing object structures without modifying the structures.
> In object-oriented programming and software engineering, the visitor design pattern is a way of
> separating an algorithm from an object structure on which it operates. A practical result of this
> separation is the ability to add new operations to existing object structures without modifying
> the structures.
**Programmatic Example**
@ -111,7 +118,7 @@ public class Soldier extends Unit {
}
```
And then some concrete visitors.
Here are then some concrete visitors.
```java
public class CommanderVisitor implements UnitVisitor {
@ -175,32 +182,39 @@ public class SoldierVisitor implements UnitVisitor {
}
```
Finally we can show the power of visitors in action.
Finally, we can show the power of visitors in action.
```java
commander.accept(new SoldierVisitor());
// Greetings soldier
// Greetings soldier
// Greetings soldier
// Greetings soldier
// Greetings soldier
// Greetings soldier
commander.accept(new SergeantVisitor());
// Hello sergeant
// Hello sergeant
commander.accept(new CommanderVisitor());
// Good to see you commander
```
Program output:
```
Greetings soldier
Greetings soldier
Greetings soldier
Greetings soldier
Greetings soldier
Greetings soldier
Hello sergeant
Hello sergeant
Good to see you commander
```
## Class diagram
![alt text](./etc/visitor_1.png "Visitor")
## Applicability
Use the Visitor pattern when
* An object structure contains many classes of objects with differing interfaces, and you want to perform operations on these objects that depend on their concrete classes
* Many distinct and unrelated operations need to be performed on objects in an object structure, and you want to avoid "polluting" their classes with these operations. Visitor lets you keep related operations together by defining them in one class. When the object structure is shared by many applications, use Visitor to put operations in just those applications that need them
* The classes defining the object structure rarely change, but you often want to define new operations over the structure. Changing the object structure classes requires redefining the interface to all visitors, which is potentially costly. If the object structure classes change often, then it's probably better to define the operations in those classes
* An object structure contains many classes of objects with differing interfaces, and you want to perform operations on these objects that depend on their concrete classes.
* Many distinct and unrelated operations need to be performed on objects in an object structure, and you want to avoid "polluting" their classes with these operations. Visitor lets you keep related operations together by defining them in one class. When the object structure is shared by many applications, use Visitor to put operations in just those applications that need them.
* The classes defining the object structure rarely change, but you often want to define new operations over the structure. Changing the object structure classes requires redefining the interface to all visitors, which is potentially costly. If the object structure classes change often, then it's probably better to define the operations in those classes.
## Real world examples