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Author SHA1 Message Date
68a5df1cc9 delete unwanted files 2021-12-29 19:05:16 +02:00
1c70cdc333 Update throttling pattern example 2021-12-29 19:00:53 +02:00
55f4ecc234 Create UpdateTest.java 2021-12-29 17:07:48 +02:00
3855f0bc15 Create AppTest.java 2021-12-29 17:07:48 +02:00
d71d2a4abd Delete UpdateTest.java 2021-12-29 17:07:48 +02:00
67f0a201e2 Delete AppTest.java 2021-12-29 17:07:47 +02:00
3f08aebcd3 Create PhysicsComponent.java 2021-12-29 17:07:47 +02:00
8604e65fce Create InputComponent.java 2021-12-29 17:07:46 +02:00
618b90147a Create GraphicsComponent.java 2021-12-29 17:07:46 +02:00
405495f0a8 Create GameObject.java 2021-12-29 17:07:45 +02:00
f9ca7f752e Create Component.java 2021-12-29 17:07:45 +02:00
b2a22e506e Create BjornPhysicsComponent.java 2021-12-29 17:07:44 +02:00
1fb1073436 Create BjornInputComponent.java 2021-12-29 17:07:44 +02:00
c28b8edf9e Create BjornGraphicsComponent.java 2021-12-29 17:07:43 +02:00
35ad973730 Update App.java 2021-12-29 17:07:43 +02:00
a4d77e65f8 Update App.java 2021-12-29 17:07:42 +02:00
0d1e226258 Create App.java 2021-12-29 17:07:42 +02:00
dc73d57f3e Delete PhysicsComponent.java 2021-12-29 17:07:41 +02:00
4f2becf96f Delete InputComponent.java 2021-12-29 17:07:41 +02:00
6fed7cbbb2 Delete GraphicsComponent.java 2021-12-29 17:07:40 +02:00
c7c3cb8e19 Delete GameObject.java 2021-12-29 17:07:40 +02:00
6bd6f07bc2 Delete Component.java 2021-12-29 17:07:39 +02:00
b0d17a00cd Delete BjornPhysicsComponent.java 2021-12-29 17:07:39 +02:00
18b3fa312f Delete BjornInputComponent.java 2021-12-29 17:07:39 +02:00
fc75edc7ca Delete BjornGraphicsComponent.java 2021-12-29 17:07:38 +02:00
c78d5a3220 Delete App.java 2021-12-29 17:07:38 +02:00
11dcf5a4aa Update App.java 2021-12-29 17:07:37 +02:00
df84a3cc74 Update Component.java 2021-12-29 17:07:37 +02:00
6523047361 Update BjornPhysicsComponent.java 2021-12-29 17:07:36 +02:00
4a4c136757 Update BjornInputComponent.java 2021-12-29 17:07:36 +02:00
1b5da55d45 Update BjornGraphicsComponent.java 2021-12-29 17:07:35 +02:00
e9b20f674e Update App.java 2021-12-29 17:07:35 +02:00
23162f474f Update pom.xml 2021-12-29 17:07:34 +02:00
1610876fdd Update README.md 2021-12-29 17:07:34 +02:00
be55b8ebb8 Update README.md 2021-12-29 17:07:33 +02:00
72aaea5333 Add files via upload 2021-12-29 17:07:33 +02:00
e62a412318 Create AppTest.java 2021-12-29 17:07:33 +02:00
ff955b4d95 Add files via upload 2021-12-29 17:07:32 +02:00
a7650013a9 Add files via upload 2021-12-29 17:07:32 +02:00
876d2a5466 Add files via upload 2021-12-29 17:07:31 +02:00
636a826bb7 Add files via upload 2021-12-29 17:07:31 +02:00
2230c55582 Create App.java 2021-12-29 17:07:30 +02:00
f003844c25 Create component.urm.puml 2021-12-29 17:07:30 +02:00
25 changed files with 167 additions and 914 deletions

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@ -1776,15 +1776,6 @@
"contributions": [
"code"
]
},
{
"login": "castleKing1997",
"name": "DragonDreamer",
"avatar_url": "https://avatars.githubusercontent.com/u/35420129?v=4",
"profile": "http://rosaecrucis.cn",
"contributions": [
"code"
]
}
],
"contributorsPerLine": 7,

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@ -10,7 +10,7 @@
[![Coverage](https://sonarcloud.io/api/project_badges/measure?project=iluwatar_java-design-patterns&metric=coverage)](https://sonarcloud.io/dashboard?id=iluwatar_java-design-patterns)
[![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)
<!-- ALL-CONTRIBUTORS-BADGE:START - Do not remove or modify this section -->
[![All Contributors](https://img.shields.io/badge/all_contributors-196-orange.svg?style=flat-square)](#contributors-)
[![All Contributors](https://img.shields.io/badge/all_contributors-195-orange.svg?style=flat-square)](#contributors-)
<!-- ALL-CONTRIBUTORS-BADGE:END -->
<br/>
@ -325,7 +325,6 @@ This project is licensed under the terms of the MIT license.
<td align="center"><a href="https://github.com/interactwithankush"><img src="https://avatars.githubusercontent.com/u/18613127?v=4?s=100" width="100px;" alt=""/><br /><sub><b>interactwithankush</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=interactwithankush" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/yuhangbin"><img src="https://avatars.githubusercontent.com/u/17566866?v=4?s=100" width="100px;" alt=""/><br /><sub><b>CharlieYu</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=yuhangbin" title="Code">💻</a></td>
<td align="center"><a href="https://github.com/Leisterbecker"><img src="https://avatars.githubusercontent.com/u/20650323?v=4?s=100" width="100px;" alt=""/><br /><sub><b>Leisterbecker</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=Leisterbecker" title="Code">💻</a></td>
<td align="center"><a href="http://rosaecrucis.cn"><img src="https://avatars.githubusercontent.com/u/35420129?v=4?s=100" width="100px;" alt=""/><br /><sub><b>DragonDreamer</b></sub></a><br /><a href="https://github.com/iluwatar/java-design-patterns/commits?author=castleKing1997" title="Code">💻</a></td>
</tr>
</table>

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@ -10,115 +10,19 @@ tags:
---
## Intent
Define a factory of immutable content with separated builder and factory interfaces.
## Explanation
Real-world example
> Imagine a magical weapon factory that can create any type of weapon wished for. When the factory
> is unboxed, the master recites the weapon types needed to prepare it. After that, any of those
> weapon types can be summoned in an instant.
In plain words
> Factory kit is a configurable object builder.
**Programmatic Example**
Let's first define the simple `Weapon` hierarchy.
```java
public interface Weapon {
}
public enum WeaponType {
SWORD,
AXE,
BOW,
SPEAR
}
public class Sword implements Weapon {
@Override
public String toString() {
return "Sword";
}
}
// Axe, Bow, and Spear are defined similarly
```
Next, we define a functional interface that allows adding a builder with a name to the factory.
```java
public interface Builder {
void add(WeaponType name, Supplier<Weapon> supplier);
}
```
The meat of the example is the `WeaponFactory` interface that effectively implements the factory
kit pattern. The method `#factory` is used to configure the factory with the classes it needs to
be able to construct. The method `#create` is then used to create object instances.
```java
public interface WeaponFactory {
static WeaponFactory factory(Consumer<Builder> consumer) {
var map = new HashMap<WeaponType, Supplier<Weapon>>();
consumer.accept(map::put);
return name -> map.get(name).get();
}
Weapon create(WeaponType name);
}
```
Now, we can show how `WeaponFactory` can be used.
```java
var factory = WeaponFactory.factory(builder -> {
builder.add(WeaponType.SWORD, Sword::new);
builder.add(WeaponType.AXE, Axe::new);
builder.add(WeaponType.SPEAR, Spear::new);
builder.add(WeaponType.BOW, Bow::new);
});
var list = new ArrayList<Weapon>();
list.add(factory.create(WeaponType.AXE));
list.add(factory.create(WeaponType.SPEAR));
list.add(factory.create(WeaponType.SWORD));
list.add(factory.create(WeaponType.BOW));
list.stream().forEach(weapon -> LOGGER.info("{}", weapon.toString()));
```
Here is the console output when the example is run.
```
21:15:49.709 [main] INFO com.iluwatar.factorykit.App - Axe
21:15:49.713 [main] INFO com.iluwatar.factorykit.App - Spear
21:15:49.713 [main] INFO com.iluwatar.factorykit.App - Sword
21:15:49.713 [main] INFO com.iluwatar.factorykit.App - Bow
```
## Class diagram
![alt text](./etc/factory-kit.png "Factory Kit")
## Applicability
Use the Factory Kit pattern when
* The factory class can't anticipate the types of objects it must create
* A new instance of a custom builder is needed instead of a global one
* The types of objects that the factory can build need to be defined outside the class
* The builder and creator interfaces need to be separated
## Related patterns
* [Builder](https://java-design-patterns.com/patterns/builder/)
* [Factory](https://java-design-patterns.com/patterns/factory/)
* a class can't anticipate the class of objects it must create
* you just want a new instance of a custom builder instead of the global one
* you explicitly want to define types of objects, that factory can build
* you want a separated builder and creator interface
## Credits
* [Design Pattern Reloaded by Remi Forax](https://www.youtube.com/watch?v=-k2X7guaArU)
* [Design Pattern Reloaded by Remi Forax: ](https://www.youtube.com/watch?v=-k2X7guaArU)

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@ -23,16 +23,14 @@
package com.iluwatar.factorykit;
import java.util.ArrayList;
import lombok.extern.slf4j.Slf4j;
/**
* Factory kit is a creational pattern that defines a factory of immutable content with separated
* Factory-kit is a creational pattern which defines a factory of immutable content with separated
* builder and factory interfaces to deal with the problem of creating one of the objects specified
* directly in the factory kit instance.
* directly in the factory-kit instance.
*
* <p>In the given example {@link WeaponFactory} represents the factory kit, that contains four
* <p>In the given example {@link WeaponFactory} represents the factory-kit, that contains four
* {@link Builder}s for creating new objects of the classes implementing {@link Weapon} interface.
*
* <p>Each of them can be called with {@link WeaponFactory#create(WeaponType)} method, with
@ -54,11 +52,7 @@ public class App {
builder.add(WeaponType.SPEAR, Spear::new);
builder.add(WeaponType.BOW, Bow::new);
});
var list = new ArrayList<Weapon>();
list.add(factory.create(WeaponType.AXE));
list.add(factory.create(WeaponType.SPEAR));
list.add(factory.create(WeaponType.SWORD));
list.add(factory.create(WeaponType.BOW));
list.stream().forEach(weapon -> LOGGER.info("{}", weapon.toString()));
var axe = factory.create(WeaponType.AXE);
LOGGER.info(axe.toString());
}
}

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@ -1,182 +0,0 @@
---
layout: pattern
title: Metadata Mapping
folder: metadata-mapping
permalink: /patterns/metadata-mapping/
categories: Architectural
language: en
tags:
- Data access
---
## Intent
Holds details of object-relational mapping in the metadata.
## Explanation
Real world example
> Hibernate ORM Tool uses Metadata Mapping Pattern to specify the mapping between classes and tables either using XML or annotations in code.
In plain words
> Metadata Mapping specifies the mapping between classes and tables so that we could treat a table of any database like a Java class.
Wikipedia says
> Create a "virtual [object database](https://en.wikipedia.org/wiki/Object_database)" that can be used from within the programming language.
**Programmatic Example**
We give an example about visiting the information of `USER` table in `h2` database. Firstly, we create `USER` table with `h2`:
```java
@Slf4j
public class DatabaseUtil {
private static final String DB_URL = "jdbc:h2:mem:metamapping";
private static final String CREATE_SCHEMA_SQL = "DROP TABLE IF EXISTS `user`;"
+ "CREATE TABLE `user` (\n"
+ " `id` int(11) NOT NULL AUTO_INCREMENT,\n"
+ " `username` varchar(255) NOT NULL,\n"
+ " `password` varchar(255) NOT NULL,\n"
+ " PRIMARY KEY (`id`)\n"
+ ");";
/**
* Create database.
*/
static {
LOGGER.info("create h2 database");
var source = new JdbcDataSource();
source.setURL(DB_URL);
try (var statement = source.getConnection().createStatement()) {
statement.execute(CREATE_SCHEMA_SQL);
} catch (SQLException e) {
LOGGER.error("unable to create h2 data source", e);
}
}
}
```
Correspondingly, here's the basic `User` entity.
```java
@Setter
@Getter
@ToString
public class User {
private Integer id;
private String username;
private String password;
/**
* Get a user.
* @param username user name
* @param password user password
*/
public User(String username, String password) {
this.username = username;
this.password = password;
}
}
```
Then we write a `xml` file to show the mapping between the table and the object:
```xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.iluwatar.metamapping.model.User" table="user">
<id name="id" type="java.lang.Integer" column="id">
<generator class="native"/>
</id>
<property name="username" column="username" type="java.lang.String"/>
<property name="password" column="password" type="java.lang.String"/>
</class>
</hibernate-mapping>
```
We use `Hibernate` to resolve the mapping and connect to our database, here's its configuration:
```xml
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- JDBC Database connection settings -->
<property name="connection.url">jdbc:h2:mem:metamapping</property>
<property name="connection.driver_class">org.h2.Driver</property>
<!-- JDBC connection pool settings ... using built-in test pool -->
<property name="connection.pool_size">1</property>
<!-- Select our SQL dialect -->
<property name="dialect">org.hibernate.dialect.H2Dialect</property>
<!-- Echo the SQL to stdout -->
<property name="show_sql">false</property>
<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">create-drop</property>
<mapping resource="com/iluwatar/metamapping/model/User.hbm.xml" />
</session-factory>
</hibernate-configuration>
```
Then we can get access to the table just like an object with `Hibernate`, here's some CRUDs:
```java
@Slf4j
public class UserService {
private static final SessionFactory factory = HibernateUtil.getSessionFactory();
/**
* List all users.
* @return list of users
*/
public List<User> listUser() {
LOGGER.info("list all users.");
List<User> users = new ArrayList<>();
try (var session = factory.openSession()) {
var tx = session.beginTransaction();
List<User> userIter = session.createQuery("FROM User").list();
for (var iterator = userIter.iterator(); iterator.hasNext();) {
users.add(iterator.next());
}
tx.commit();
} catch (HibernateException e) {
LOGGER.debug("fail to get users", e);
}
return users;
}
// other CRUDs ->
...
public void close() {
HibernateUtil.shutdown();
}
}
```
## Class diagram
![metamapping](etc/metamapping.png)
## Applicability
Use the Metadata Mapping when:
- you want reduce the amount of work needed to handle database mapping.
## Known uses
[Hibernate](https://hibernate.org/), [EclipseLink](https://www.eclipse.org/eclipselink/), [MyBatis](https://blog.mybatis.org/)......
## Credits
- [J2EE Design Patterns](https://www.amazon.com/gp/product/0596004273/ref=as_li_tl?ie=UTF8&camp=1789&creative=9325&creativeASIN=0596004273&linkCode=as2&tag=javadesignpat-20&linkId=48d37c67fb3d845b802fa9b619ad8f31)

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@ -1,32 +0,0 @@
@startuml
interface com.iluwatar.metamapping.service.UserService {
+ List<User> listUser()
+ int createUser(User)
+ void updateUser(Integer,User)
+ void deleteUser(Integer)
+ User getUser(Integer)
+ void close()
}
class com.iluwatar.metamapping.utils.DatabaseUtil {
+ {static} void createDataSource()
}
class com.iluwatar.metamapping.model.User {
- Integer id
- String username
- String password
+ User(String username, String password)
}
class com.iluwatar.metamapping.utils.HibernateUtil {
+ {static} SessionFactory getSessionFactory()
+ {static} void shutdown()
}
class com.iluwatar.metamapping.App {
+ {static} void main(String[])
+ {static} List<User> generateSampleUsers()
}
com.iluwatar.metamapping.service.UserService <.. com.iluwatar.metamapping.App
com.iluwatar.metamapping.model.User <.. com.iluwatar.metamapping.service.UserService
com.iluwatar.metamapping.utils.HibernateUtil <.. com.iluwatar.metamapping.service.UserService
com.iluwatar.metamapping.utils.DatabaseUtil <-- com.iluwatar.metamapping.utils.HibernateUtil
@enduml

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@ -1,87 +0,0 @@
<?xml version="1.0" encoding="UTF-8"?>
<!--
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 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>1.26.0-SNAPSHOT</version>
</parent>
<modelVersion>4.0.0</modelVersion>
<artifactId>metadata-mapping</artifactId>
<dependencies>
<dependency>
<groupId>org.junit.jupiter</groupId>
<artifactId>junit-jupiter-engine</artifactId>
<scope>test</scope>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
</dependency>
<dependency>
<groupId>org.hibernate</groupId>
<artifactId>hibernate-core</artifactId>
</dependency>
<dependency>
<groupId>com.h2database</groupId>
<artifactId>h2</artifactId>
</dependency>
<dependency>
<groupId>javax.xml.bind</groupId>
<artifactId>jaxb-api</artifactId>
</dependency>
<dependency>
<groupId>com.sun.xml.bind</groupId>
<artifactId>jaxb-impl</artifactId>
</dependency>
<dependency>
<groupId>com.sun.istack</groupId>
<artifactId>istack-commons-runtime</artifactId>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-assembly-plugin</artifactId>
<executions>
<execution>
<configuration>
<archive>
<manifest>
<mainClass>com.iluwatar.metamapping.App</mainClass>
</manifest>
</archive>
</configuration>
</execution>
</executions>
</plugin>
</plugins>
</build>
</project>

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@ -1,72 +0,0 @@
package com.iluwatar.metamapping;
import com.iluwatar.metamapping.model.User;
import com.iluwatar.metamapping.service.UserService;
import com.iluwatar.metamapping.utils.DatabaseUtil;
import java.util.List;
import lombok.extern.slf4j.Slf4j;
import org.hibernate.service.ServiceRegistry;
/**
* Metadata Mapping specifies the mapping
* between classes and tables so that
* we could treat a table of any database like a Java class.
*
* <p>With hibernate, we achieve list/create/update/delete/get operations:
* 1)Create the H2 Database in {@link DatabaseUtil}.
* 2)Hibernate resolve hibernate.cfg.xml and generate service like save/list/get/delete.
* For learning metadata mapping pattern, we go deeper into Hibernate here:
* a)read properties from hibernate.cfg.xml and mapping from *.hbm.xml
* b)create session factory to generate session interacting with database
* c)generate session with factory pattern
* d)create query object or use basic api with session,
* hibernate will convert all query to database query according to metadata
* 3)We encapsulate hibernate service in {@link UserService} for our use.
* @see org.hibernate.cfg.Configuration#configure(String)
* @see org.hibernate.cfg.Configuration#buildSessionFactory(ServiceRegistry)
* @see org.hibernate.internal.SessionFactoryImpl#openSession()
*/
@Slf4j
public class App {
/**
* Program entry point.
*
* @param args command line args.
* @throws Exception if any error occurs.
*/
public static void main(String[] args) throws Exception {
// get service
var userService = new UserService();
// use create service to add users
for (var user: generateSampleUsers()) {
var id = userService.createUser(user);
LOGGER.info("Add user" + user + "at" + id + ".");
}
// use list service to get users
var users = userService.listUser();
LOGGER.info(String.valueOf(users));
// use get service to get a user
var user = userService.getUser(1);
LOGGER.info(String.valueOf(user));
// change password of user 1
user.setPassword("new123");
// use update service to update user 1
userService.updateUser(1, user);
// use delete service to delete user 2
userService.deleteUser(2);
// close service
userService.close();
}
/**
* Generate users.
*
* @return list of users.
*/
public static List<User> generateSampleUsers() {
final var user1 = new User("ZhangSan", "zhs123");
final var user2 = new User("LiSi", "ls123");
final var user3 = new User("WangWu", "ww123");
return List.of(user1, user2, user3);
}
}

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@ -1,29 +0,0 @@
package com.iluwatar.metamapping.model;
import lombok.Getter;
import lombok.Setter;
import lombok.ToString;
/**
* User Entity.
*/
@Setter
@Getter
@ToString
public class User {
private Integer id;
private String username;
private String password;
public User() {}
/**
* Get a user.
* @param username user name
* @param password user password
*/
public User(String username, String password) {
this.username = username;
this.password = password;
}
}

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@ -1,114 +0,0 @@
package com.iluwatar.metamapping.service;
import com.iluwatar.metamapping.model.User;
import com.iluwatar.metamapping.utils.HibernateUtil;
import java.util.ArrayList;
import java.util.List;
import lombok.extern.slf4j.Slf4j;
import org.hibernate.HibernateException;
import org.hibernate.SessionFactory;
/**
* Service layer for user.
*/
@Slf4j
public class UserService {
private static final SessionFactory factory = HibernateUtil.getSessionFactory();
/**
* List all users.
* @return list of users
*/
public List<User> listUser() {
LOGGER.info("list all users.");
List<User> users = new ArrayList<>();
try (var session = factory.openSession()) {
var tx = session.beginTransaction();
List<User> userIter = session.createQuery("FROM User").list();
for (var iterator = userIter.iterator(); iterator.hasNext();) {
users.add(iterator.next());
}
tx.commit();
} catch (HibernateException e) {
LOGGER.debug("fail to get users", e);
}
return users;
}
/**
* Add a user.
* @param user user entity
* @return user id
*/
public int createUser(User user) {
LOGGER.info("create user: " + user.getUsername());
var id = -1;
try (var session = factory.openSession()) {
var tx = session.beginTransaction();
id = (Integer) session.save(user);
tx.commit();
} catch (HibernateException e) {
LOGGER.debug("fail to create user", e);
}
LOGGER.info("create user " + user.getUsername() + " at " + id);
return id;
}
/**
* Update user.
* @param id user id
* @param user new user entity
*/
public void updateUser(Integer id, User user) {
LOGGER.info("update user at " + id);
try (var session = factory.openSession()) {
var tx = session.beginTransaction();
user.setId(id);
session.update(user);
tx.commit();
} catch (HibernateException e) {
LOGGER.debug("fail to update user", e);
}
}
/**
* Delete user.
* @param id user id
*/
public void deleteUser(Integer id) {
LOGGER.info("delete user at: " + id);
try (var session = factory.openSession()) {
var tx = session.beginTransaction();
var user = session.get(User.class, id);
session.delete(user);
tx.commit();
} catch (HibernateException e) {
LOGGER.debug("fail to delete user", e);
}
}
/**
* Get user.
* @param id user id
* @return deleted user
*/
public User getUser(Integer id) {
LOGGER.info("get user at: " + id);
User user = null;
try (var session = factory.openSession()) {
var tx = session.beginTransaction();
user = session.get(User.class, id);
tx.commit();
} catch (HibernateException e) {
LOGGER.debug("fail to get user", e);
}
return user;
}
/**
* Close hibernate.
*/
public void close() {
HibernateUtil.shutdown();
}
}

View File

@ -1,39 +0,0 @@
package com.iluwatar.metamapping.utils;
import java.sql.SQLException;
import lombok.extern.slf4j.Slf4j;
import org.h2.jdbcx.JdbcDataSource;
/**
* Create h2 database.
*/
@Slf4j
public class DatabaseUtil {
private static final String DB_URL = "jdbc:h2:mem:metamapping";
private static final String CREATE_SCHEMA_SQL = "DROP TABLE IF EXISTS `user`;"
+ "CREATE TABLE `user` (\n"
+ " `id` int(11) NOT NULL AUTO_INCREMENT,\n"
+ " `username` varchar(255) NOT NULL,\n"
+ " `password` varchar(255) NOT NULL,\n"
+ " PRIMARY KEY (`id`)\n"
+ ");";
/**
* Hide constructor.
*/
private DatabaseUtil() {}
/**
* Create database.
*/
static {
LOGGER.info("create h2 database");
var source = new JdbcDataSource();
source.setURL(DB_URL);
try (var statement = source.getConnection().createStatement()) {
statement.execute(CREATE_SCHEMA_SQL);
} catch (SQLException e) {
LOGGER.error("unable to create h2 data source", e);
}
}
}

View File

@ -1,45 +0,0 @@
package com.iluwatar.metamapping.utils;
import lombok.extern.slf4j.Slf4j;
import org.hibernate.SessionFactory;
import org.hibernate.cfg.Configuration;
/**
* Manage hibernate.
*/
@Slf4j
public class HibernateUtil {
private static final SessionFactory sessionFactory = buildSessionFactory();
/**
* Hide constructor.
*/
private HibernateUtil() {}
/**
* Build session factory.
* @return session factory
*/
private static SessionFactory buildSessionFactory() {
// Create the SessionFactory from hibernate.cfg.xml
return new Configuration().configure().buildSessionFactory();
}
/**
* Get session factory.
* @return session factory
*/
public static SessionFactory getSessionFactory() {
return sessionFactory;
}
/**
* Close session factory.
*/
public static void shutdown() {
// Close caches and connection pools
getSessionFactory().close();
}
}

View File

@ -1,14 +0,0 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-mapping PUBLIC
"-//Hibernate/Hibernate Mapping DTD//EN"
"http://www.hibernate.org/dtd/hibernate-mapping-3.0.dtd">
<hibernate-mapping>
<class name="com.iluwatar.metamapping.model.User" table="user">
<id name="id" type="java.lang.Integer" column="id">
<generator class="native"/>
</id>
<property name="username" column="username" type="java.lang.String"/>
<property name="password" column="password" type="java.lang.String"/>
</class>
</hibernate-mapping>

View File

@ -1,20 +0,0 @@
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE hibernate-configuration PUBLIC
"-//Hibernate/Hibernate Configuration DTD 3.0//EN"
"http://hibernate.sourceforge.net/hibernate-configuration-3.0.dtd">
<hibernate-configuration>
<session-factory>
<!-- JDBC Database connection settings -->
<property name="connection.url">jdbc:h2:mem:metamapping</property>
<property name="connection.driver_class">org.h2.Driver</property>
<!-- JDBC connection pool settings ... using built-in test pool -->
<property name="connection.pool_size">1</property>
<!-- Select our SQL dialect -->
<property name="dialect">org.hibernate.dialect.H2Dialect</property>
<!-- Echo the SQL to stdout -->
<property name="show_sql">false</property>
<!-- Drop and re-create the database schema on startup -->
<property name="hbm2ddl.auto">create-drop</property>
<mapping resource="com/iluwatar/metamapping/model/User.hbm.xml" />
</session-factory>
</hibernate-configuration>

View File

@ -1,20 +0,0 @@
package com.iluwatar.metamapping;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertDoesNotThrow;
/**
* Tests that metadata mapping example runs without errors.
*/
class AppTest {
/**
* Issue: Add at least one assertion to this test case.
*
* Solution: Inserted assertion to check whether the execution of the main method in {@link App#main(String[])}
* throws an exception.
*/
@Test
void shouldExecuteMetaMappingWithoutException() {
assertDoesNotThrow(() -> App.main(new String[]{}));
}
}

View File

@ -75,7 +75,6 @@
<license-maven-plugin.version>3.0</license-maven-plugin.version>
<urm-maven-plugin.version>1.4.8</urm-maven-plugin.version>
<commons-io.version>2.7</commons-io.version>
<istack-commons-runtime.version>4.0.1</istack-commons-runtime.version>
<!-- SonarCloud -->
<sonar.host.url>https://sonarcloud.io</sonar.host.url>
<sonar.organization>iluwatar</sonar.organization>
@ -228,7 +227,6 @@
<module>lockable-object</module>
<module>fanout-fanin</module>
<module>domain-model</module>
<module>metadata-mapping</module>
</modules>
<repositories>
<repository>
@ -379,11 +377,6 @@
<artifactId>commons-io</artifactId>
<version>${commons-io.version}</version>
</dependency>
<dependency>
<groupId>com.sun.istack</groupId>
<artifactId>istack-commons-runtime</artifactId>
<version>${istack-commons-runtime.version}</version>
</dependency>
</dependencies>
</dependencyManagement>
<dependencies>

View File

@ -18,11 +18,11 @@ threads and eliminating the latency of creating new threads.
## Explanation
Real world example
Real-world example
> We have a large number of relatively short tasks at hand. We need to peel huge amounts of potatoes
> and serve mighty amount of coffee cups. Creating a new thread for each task would be a waste so we
> establish a thread pool.
> and serve a mighty amount of coffee cups. Creating a new thread for each task would be a waste so
> we establish a thread pool.
In plain words
@ -99,7 +99,7 @@ public class PotatoPeelingTask extends Task {
}
```
Next we present a runnable `Worker` class that the thread pool will utilize to handle all the potato
Next, we present a runnable `Worker` class that the thread pool will utilize to handle all the potato
peeling and coffee making.
```java

View File

@ -16,10 +16,12 @@ Ensure that a given client is not able to access service resources more than the
## Explanation
Real world example
Real-world example
> A large multinational corporation offers API to its customers. The API is rate-limited and each
> customer can only make certain amount of calls per second.
> A young human and an old dwarf walk into a bar. They start ordering beers from the bartender.
> The bartender immediately sees that the young human shouldn't consume too many drinks too fast
> and refuses to serve if enough time has not passed. For the old dwarf, the serving rate can
> be higher.
In plain words
@ -33,30 +35,25 @@ In plain words
**Programmatic Example**
Tenant class presents the clients of the API. CallsCount tracks the number of API calls per tenant.
`BarCustomer` class presents the clients of the `Bartender` API. `CallsCount` tracks the number of
calls per `BarCustomer`.
```java
public class Tenant {
public class BarCustomer {
private final String name;
private final int allowedCallsPerSecond;
@Getter
private final String name;
@Getter
private final int allowedCallsPerSecond;
public Tenant(String name, int allowedCallsPerSecond, CallsCount callsCount) {
if (allowedCallsPerSecond < 0) {
throw new InvalidParameterException("Number of calls less than 0 not allowed");
public BarCustomer(String name, int allowedCallsPerSecond, CallsCount callsCount) {
if (allowedCallsPerSecond < 0) {
throw new InvalidParameterException("Number of calls less than 0 not allowed");
}
this.name = name;
this.allowedCallsPerSecond = allowedCallsPerSecond;
callsCount.addTenant(name);
}
this.name = name;
this.allowedCallsPerSecond = allowedCallsPerSecond;
callsCount.addTenant(name);
}
public String getName() {
return name;
}
public int getAllowedCallsPerSecond() {
return allowedCallsPerSecond;
}
}
@Slf4j
@ -76,14 +73,14 @@ public final class CallsCount {
}
public void reset() {
LOGGER.debug("Resetting the map.");
tenantCallsCount.replaceAll((k, v) -> new AtomicLong(0));
LOGGER.info("reset counters");
}
}
```
Next we introduce the service that the tenants are calling. To track the call count we use the
throttler timer.
Next, the service that the tenants are calling is introduced. To track the call count, a throttler
timer is used.
```java
public interface Throttler {
@ -111,71 +108,103 @@ public class ThrottleTimerImpl implements Throttler {
}, 0, throttlePeriod);
}
}
```
class B2BService {
`Bartender` offers the `orderDrink` service to the `BarCustomer`s. The customers probably don't
know that the beer serving rate is limited by their appearances.
private static final Logger LOGGER = LoggerFactory.getLogger(B2BService.class);
private final CallsCount callsCount;
```java
class Bartender {
public B2BService(Throttler timer, CallsCount callsCount) {
this.callsCount = callsCount;
timer.start();
}
private static final Logger LOGGER = LoggerFactory.getLogger(Bartender.class);
private final CallsCount callsCount;
public int dummyCustomerApi(Tenant tenant) {
var tenantName = tenant.getName();
var count = callsCount.getCount(tenantName);
LOGGER.debug("Counter for {} : {} ", tenant.getName(), count);
if (count >= tenant.getAllowedCallsPerSecond()) {
LOGGER.error("API access per second limit reached for: {}", tenantName);
return -1;
public Bartender(Throttler timer, CallsCount callsCount) {
this.callsCount = callsCount;
timer.start();
}
callsCount.incrementCount(tenantName);
return getRandomCustomerId();
}
private int getRandomCustomerId() {
return ThreadLocalRandom.current().nextInt(1, 10000);
}
public int orderDrink(BarCustomer barCustomer) {
var tenantName = barCustomer.getName();
var count = callsCount.getCount(tenantName);
if (count >= barCustomer.getAllowedCallsPerSecond()) {
LOGGER.error("I'm sorry {}, you've had enough for today!", tenantName);
return -1;
}
callsCount.incrementCount(tenantName);
LOGGER.debug("Serving beer to {} : [{} consumed] ", barCustomer.getName(), count+1);
return getRandomCustomerId();
}
private int getRandomCustomerId() {
return ThreadLocalRandom.current().nextInt(1, 10000);
}
}
```
Now we are ready to see the full example in action. Tenant Adidas is rate-limited to 5 calls per
second and Nike to 6.
Now it is possible to see the full example in action. `BarCustomer` young human is rate-limited to 2
calls per second and the old dwarf to 4.
```java
public static void main(String[] args) {
public static void main(String[] args) {
var callsCount = new CallsCount();
var adidas = new Tenant("Adidas", 5, callsCount);
var nike = new Tenant("Nike", 6, callsCount);
var human = new BarCustomer("young human", 2, callsCount);
var dwarf = new BarCustomer("dwarf soldier", 4, callsCount);
var executorService = Executors.newFixedThreadPool(2);
executorService.execute(() -> makeServiceCalls(adidas, callsCount));
executorService.execute(() -> makeServiceCalls(nike, callsCount));
executorService.shutdown();
try {
executorService.awaitTermination(10, TimeUnit.SECONDS);
} catch (InterruptedException e) {
LOGGER.error("Executor Service terminated: {}", e.getMessage());
}
}
private static void makeServiceCalls(Tenant tenant, CallsCount callsCount) {
var timer = new ThrottleTimerImpl(10, callsCount);
var service = new B2BService(timer, callsCount);
executorService.execute(() -> makeServiceCalls(human, callsCount));
executorService.execute(() -> makeServiceCalls(dwarf, callsCount));
executorService.shutdown();
try {
executorService.awaitTermination(10, TimeUnit.SECONDS);
} catch (InterruptedException e) {
LOGGER.error("Executor service terminated: {}", e.getMessage());
}
}
private static void makeServiceCalls(BarCustomer barCustomer, CallsCount callsCount) {
var timer = new ThrottleTimerImpl(1000, callsCount);
var service = new Bartender(timer, callsCount);
// Sleep is introduced to keep the output in check and easy to view and analyze the results.
IntStream.range(0, 20).forEach(i -> {
service.dummyCustomerApi(tenant);
try {
Thread.sleep(1);
} catch (InterruptedException e) {
LOGGER.error("Thread interrupted: {}", e.getMessage());
}
IntStream.range(0, 50).forEach(i -> {
service.orderDrink(barCustomer);
try {
Thread.sleep(100);
} catch (InterruptedException e) {
LOGGER.error("Thread interrupted: {}", e.getMessage());
}
});
}
}
```
An excerpt from the example's console output:
```
18:46:36.218 [Timer-0] INFO com.iluwatar.throttling.CallsCount - reset counters
18:46:36.218 [Timer-1] INFO com.iluwatar.throttling.CallsCount - reset counters
18:46:36.242 [pool-1-thread-2] DEBUG com.iluwatar.throttling.Bartender - Serving beer to dwarf soldier : [1 consumed]
18:46:36.242 [pool-1-thread-1] DEBUG com.iluwatar.throttling.Bartender - Serving beer to young human : [1 consumed]
18:46:36.342 [pool-1-thread-2] DEBUG com.iluwatar.throttling.Bartender - Serving beer to dwarf soldier : [2 consumed]
18:46:36.342 [pool-1-thread-1] DEBUG com.iluwatar.throttling.Bartender - Serving beer to young human : [2 consumed]
18:46:36.443 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
18:46:36.443 [pool-1-thread-2] DEBUG com.iluwatar.throttling.Bartender - Serving beer to dwarf soldier : [3 consumed]
18:46:36.544 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
18:46:36.544 [pool-1-thread-2] DEBUG com.iluwatar.throttling.Bartender - Serving beer to dwarf soldier : [4 consumed]
18:46:36.645 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
18:46:36.645 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
18:46:36.745 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
18:46:36.745 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
18:46:36.846 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
18:46:36.846 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
18:46:36.947 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
18:46:36.947 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
18:46:37.048 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
18:46:37.048 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
18:46:37.148 [pool-1-thread-1] ERROR com.iluwatar.throttling.Bartender - I'm sorry young human, you've had enough for today!
18:46:37.148 [pool-1-thread-2] ERROR com.iluwatar.throttling.Bartender - I'm sorry dwarf soldier, you've had enough for today!
```
## Class diagram
@ -185,7 +214,7 @@ second and Nike to 6.
The Throttling pattern should be used:
* When a service access needs to be restricted to not have high impacts on the performance of the service.
* When service access needs to be restricted not to have high impact on the performance of the service.
* When multiple clients are consuming the same service resources and restriction has to be made according to the usage per client.
## Credits

View File

@ -34,11 +34,11 @@ import lombok.extern.slf4j.Slf4j;
* complete service by users or a particular tenant. This can allow systems to continue to function
* and meet service level agreements, even when an increase in demand places load on resources.
* <p>
* In this example we have ({@link App}) as the initiating point of the service. This is a time
* In this example there is a {@link Bartender} serving beer to {@link BarCustomer}s. This is a time
* based throttling, i.e. only a certain number of calls are allowed per second.
* </p>
* ({@link Tenant}) is the Tenant POJO class with which many tenants can be created ({@link
* B2BService}) is the service which is consumed by the tenants and is throttled.
* ({@link BarCustomer}) is the service tenant class having a name and the number of calls allowed.
* ({@link Bartender}) is the service which is consumed by the tenants and is throttled.
*/
@Slf4j
public class App {
@ -50,33 +50,35 @@ public class App {
*/
public static void main(String[] args) {
var callsCount = new CallsCount();
var adidas = new Tenant("Adidas", 5, callsCount);
var nike = new Tenant("Nike", 6, callsCount);
var human = new BarCustomer("young human", 2, callsCount);
var dwarf = new BarCustomer("dwarf soldier", 4, callsCount);
var executorService = Executors.newFixedThreadPool(2);
executorService.execute(() -> makeServiceCalls(adidas, callsCount));
executorService.execute(() -> makeServiceCalls(nike, callsCount));
executorService.execute(() -> makeServiceCalls(human, callsCount));
executorService.execute(() -> makeServiceCalls(dwarf, callsCount));
executorService.shutdown();
try {
executorService.awaitTermination(10, TimeUnit.SECONDS);
if (!executorService.awaitTermination(10, TimeUnit.SECONDS)) {
executorService.shutdownNow();
}
} catch (InterruptedException e) {
LOGGER.error("Executor Service terminated: {}", e.getMessage());
executorService.shutdownNow();
}
}
/**
* Make calls to the B2BService dummy API.
* Make calls to the bartender.
*/
private static void makeServiceCalls(Tenant tenant, CallsCount callsCount) {
var timer = new ThrottleTimerImpl(10, callsCount);
var service = new B2BService(timer, callsCount);
private static void makeServiceCalls(BarCustomer barCustomer, CallsCount callsCount) {
var timer = new ThrottleTimerImpl(1000, callsCount);
var service = new Bartender(timer, callsCount);
// Sleep is introduced to keep the output in check and easy to view and analyze the results.
IntStream.range(0, 20).forEach(i -> {
service.dummyCustomerApi(tenant);
IntStream.range(0, 50).forEach(i -> {
service.orderDrink(barCustomer);
try {
Thread.sleep(1);
Thread.sleep(100);
} catch (InterruptedException e) {
LOGGER.error("Thread interrupted: {}", e.getMessage());
}

View File

@ -25,22 +25,26 @@ package com.iluwatar.throttling;
import java.security.InvalidParameterException;
/**
* A Pojo class to create a basic Tenant with the allowed calls per second.
*/
public class Tenant {
import lombok.Getter;
/**
* BarCustomer is a tenant with a name and a number of allowed calls per second.
*/
public class BarCustomer {
@Getter
private final String name;
@Getter
private final int allowedCallsPerSecond;
/**
* Constructor.
*
* @param name Name of the tenant
* @param allowedCallsPerSecond The number of calls allowed for a particular tenant.
* @param name Name of the BarCustomer
* @param allowedCallsPerSecond The number of calls allowed for this particular tenant.
* @throws InvalidParameterException If number of calls is less than 0, throws exception.
*/
public Tenant(String name, int allowedCallsPerSecond, CallsCount callsCount) {
public BarCustomer(String name, int allowedCallsPerSecond, CallsCount callsCount) {
if (allowedCallsPerSecond < 0) {
throw new InvalidParameterException("Number of calls less than 0 not allowed");
}
@ -48,12 +52,4 @@ public class Tenant {
this.allowedCallsPerSecond = allowedCallsPerSecond;
callsCount.addTenant(name);
}
public String getName() {
return name;
}
public int getAllowedCallsPerSecond() {
return allowedCallsPerSecond;
}
}

View File

@ -29,33 +29,32 @@ import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
/**
* A service which accepts a tenant and throttles the resource based on the time given to the
* tenant.
* Bartender is a service which accepts a BarCustomer (tenant) and throttles
* the resource based on the time given to the tenant.
*/
class B2BService {
class Bartender {
private static final Logger LOGGER = LoggerFactory.getLogger(B2BService.class);
private static final Logger LOGGER = LoggerFactory.getLogger(Bartender.class);
private final CallsCount callsCount;
public B2BService(Throttler timer, CallsCount callsCount) {
public Bartender(Throttler timer, CallsCount callsCount) {
this.callsCount = callsCount;
timer.start();
}
/**
* Calls dummy customer api.
*
* Orders a drink from the bartender.
* @return customer id which is randomly generated
*/
public int dummyCustomerApi(Tenant tenant) {
var tenantName = tenant.getName();
public int orderDrink(BarCustomer barCustomer) {
var tenantName = barCustomer.getName();
var count = callsCount.getCount(tenantName);
LOGGER.debug("Counter for {} : {} ", tenant.getName(), count);
if (count >= tenant.getAllowedCallsPerSecond()) {
LOGGER.error("API access per second limit reached for: {}", tenantName);
if (count >= barCustomer.getAllowedCallsPerSecond()) {
LOGGER.error("I'm sorry {}, you've had enough for today!", tenantName);
return -1;
}
callsCount.incrementCount(tenantName);
LOGGER.debug("Serving beer to {} : [{} consumed] ", barCustomer.getName(), count + 1);
return getRandomCustomerId();
}

View File

@ -69,7 +69,7 @@ public final class CallsCount {
* Resets the count of all the tenants in the map.
*/
public void reset() {
LOGGER.debug("Resetting the map.");
tenantCallsCount.replaceAll((k, v) -> new AtomicLong(0));
LOGGER.info("reset counters");
}
}

View File

@ -23,20 +23,21 @@
package com.iluwatar.throttling;
import static org.junit.jupiter.api.Assertions.assertThrows;
import org.junit.jupiter.api.Test;
import java.security.InvalidParameterException;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertThrows;
/**
* TenantTest to test the creation of Tenant with valid parameters.
*/
public class TenantTest {
public class BarCustomerTest {
@Test
void constructorTest() {
assertThrows(InvalidParameterException.class, () -> {
new Tenant("FailTenant", -1, new CallsCount());
new BarCustomer("sirBrave", -1, new CallsCount());
});
}
}

View File

@ -32,19 +32,18 @@ import org.junit.jupiter.api.Test;
/**
* B2BServiceTest class to test the B2BService
*/
public class B2BServiceTest {
public class BartenderTest {
private final CallsCount callsCount = new CallsCount();
@Test
void dummyCustomerApiTest() {
var tenant = new Tenant("testTenant", 2, callsCount);
var tenant = new BarCustomer("pirate", 2, callsCount);
// In order to assure that throttling limits will not be reset, we use an empty throttling implementation
var timer = (Throttler) () -> {
};
var service = new B2BService(timer, callsCount);
var timer = (Throttler) () -> {};
var service = new Bartender(timer, callsCount);
IntStream.range(0, 5).mapToObj(i -> tenant).forEach(service::dummyCustomerApi);
IntStream.range(0, 5).mapToObj(i -> tenant).forEach(service::orderDrink);
var counter = callsCount.getCount(tenant.getName());
assertEquals(2, counter, "Counter limit must be reached");
}