<div id="readability-page-1" class="page"><div><h2 data-ke-size="size26"><b>비즈니스 규칙 엔진이란?</b></h2>
<p data-ke-size="size16">비즈니스 규칙 엔진이란, 어떤 조건에 따라 액션을 유발하는 규칙이 있는 비즈니스 기능을 구현할 때 사용하는 프로그램이다.&nbsp;</p>
<p data-ke-size="size16">비즈니스 규칙 엔진의 요구사항은 크게 4가지로 나뉜다.</p>
<ul data-ke-list-type="disc">
<li>팩트 : 규칙이 확인할 수 있는 정보</li>
<li>액션 : 수행하려는 동작</li>
<li>조건 : 액션을 언제 발생시킬지 지정</li>
<li>규칙 : 실행하려는 비즈니스 규칙을 지정
<ul data-ke-list-type="disc">
<li>보통 팩트/액션/조건을 한 그룹으로 묶어서 규칙으로 만든다.</li>
</ul>
</li>
</ul>
<p data-ke-size="size16">비즈니스 규칙 엔진 구현 방법은 다음과 같다.</p>
<h2 data-ke-size="size26"><b>Diagram</b></h2>
<figure data-origin-width="1116" data-origin-height="633" data-ke-mobilestyle="alignCenter"><span data-url="https://blog.kakaocdn.net/dn/clt98U/btrEullGhy6/rlRCmWZbkHe1SKoeaSgXg0/img.png" data-lightbox="lightbox" data-alt=""><img src="https://blog.kakaocdn.net/dn/clt98U/btrEullGhy6/rlRCmWZbkHe1SKoeaSgXg0/img.png" data-filename="mermaid-diagram-20220611163810.png" data-ke-mobilestyle="alignCenter"></span></figure>
<h2 data-ke-size="size26"><b>Code</b></h2>
<h4 data-ke-size="size20">Class</h4>
<pre id="code_1654909201960" data-ke-language="java" data-ke-type="codeblock"><code>@FunctionalInterface
public interface Action {

  void execute(Facts facts);
}</code></pre>

<pre id="code_1654909227398" data-ke-language="java" data-ke-type="codeblock"><code>@FunctionalInterface
public interface Condition {
  boolean evaluate(Facts facts);
}</code></pre>

<pre id="code_1654909229346" data-ke-language="java" data-ke-type="codeblock"><code>@FunctionalInterface 
interface Rule {
  void perform(Facts facts);
}

// @FunctionalInterface (함수형 인터페이스)란 1 개의 추상 메소드를 갖는 인터페이스를 말한다.</code></pre>

<pre id="code_1654909166520" data-ke-language="java" data-ke-type="codeblock"><code>class DefaultRule implements Rule {
  private final Condition condition;
  private final Action action;

  public DefaultRule(final Condition condition, final Action action) {
    this.condition = condition;
    this.action = action;
  }

  @Override
  public void perform(Facts facts) {
    if(condition.evaluate(facts)) {
      action.execute(facts);
    }
  }
}</code></pre>

<pre id="code_1654909169713" data-ke-language="java" data-ke-type="codeblock"><code>public class RuleBuilder {
  private Condition condition;

  private RuleBuilder(final Condition condition) {
    this.condition = condition;
  }

  public static RuleBuilder when(final Condition condition) {
    return new RuleBuilder(condition);
  }

  public Rule then(final Action action) {
    return new DefaultRule(condition, action);
  }

}</code></pre>

<pre id="code_1654909280231" data-ke-language="java" data-ke-type="codeblock"><code>import java.util.HashMap;
import java.util.Map;

public class Facts {

  private final Map&lt;String, String&gt; facts = new HashMap&lt;&gt;();

  public String getFact(final String name) {
    return this.facts.get(name);
  }

  public void addFact(final String name, final String value) {
    this.facts.put(name, value);
  }

}</code></pre>

<pre id="code_1654908969029" data-ke-language="java" data-ke-type="codeblock"><code>import java.util.ArrayList;
import java.util.List;

public class BusinessRuleEngine {

  private final List&lt;Rule&gt; rules;
  private final Facts facts;

  public BusinessRuleEngine(final Facts facts) {
    this.rules = new ArrayList&lt;&gt;();
    this.facts = facts;
  }

  public void addRule(final Rule rule) {
    this.rules.add(rule);
  }

  public void run() {
    this.rules.forEach(rule -&gt; rule.perform(facts));
  }

}</code></pre>

<h4 data-ke-size="size20">Client</h4>
<pre id="code_1654909251878" data-ke-language="java" data-ke-type="codeblock"><code>final Rule ruleSendEmailToSalesWhenCEO = RuleBuilder
        .when(facts -&gt; "CEO".equals(facts.getFact("jobTitle")))
        .then(facts -&gt; {
          var name = facts.getFact("name");
          Mailer.sendEmail("sales@company.com", "Relevant customer: " + name);
        });
        
final facts = new Facts();
facts.addFact("name", "김복세");
facts.addFact("jobTitle", "CEO");

final BusinessRuleEngine businessRuleEngine = new BusinessRuleEngine(facts);
businessRuleEngine.addRule(ruleSendEmailToSalesWhenCEO);
businessRuleEngine.run();</code></pre>

<h2 data-ke-size="size26"><b>참고</b></h2>
<p data-ke-size="size16">실전 자바 소프트웨어 개발 5장. 비즈니스 규칙 엔진</p>
<p data-ke-size="size16"><a href="https://github.com/sojeongw/real-world-software-development/tree/main/buisiness-rule-engine" target="_blank" rel="noopener">https://github.com/sojeongw/real-world-software-development/tree/main/buisiness-rule-engine</a></p>
<p data-ke-size="size16"><a href="https://sabarada.tistory.com/72" target="_blank" rel="noopener">https://sabarada.tistory.com/72</a></p>
<figure id="og_1654910517621" contenteditable="false" data-ke-type="opengraph" data-ke-align="alignCenter" data-og-type="object" data-og-title="GitHub - sojeongw/real-world-software-development: 실전 자바 소프트웨어 개발" data-og-description="실전 자바 소프트웨어 개발. Contribute to sojeongw/real-world-software-development development by creating an account on GitHub." data-og-host="github.com" data-og-source-url="https://github.com/sojeongw/real-world-software-development/tree/main/buisiness-rule-engine" data-og-url="https://github.com/sojeongw/real-world-software-development" data-og-image="https://scrap.kakaocdn.net/dn/bHlPaC/hyOIbyyhE0/76qo0KgNmM5VcKJ7B0cPL1/img.png?width=1200&amp;height=600&amp;face=0_0_1200_600"><a href="https://github.com/sojeongw/real-world-software-development/tree/main/buisiness-rule-engine" target="_blank" rel="noopener" data-source-url="https://github.com/sojeongw/real-world-software-development/tree/main/buisiness-rule-engine">

<div>
<p data-ke-size="size16">GitHub - sojeongw/real-world-software-development: 실전 자바 소프트웨어 개발</p>
<p data-ke-size="size16">실전 자바 소프트웨어 개발. Contribute to sojeongw/real-world-software-development development by creating an account on GitHub.</p>
<p data-ke-size="size16">github.com</p>
</div>
</a><img src="https://scrap.kakaocdn.net/dn/bHlPaC/hyOIbyyhE0/76qo0KgNmM5VcKJ7B0cPL1/img.png?width=1200&amp;height=600&amp;face=0_0_1200_600"></figure>
<pre id="code_1654910279079" data-ke-language="java" data-ke-type="codeblock"><code> classDiagram
      DefaultRule ..|&gt;	Rule : Realization(실체화)
      BusinessRuleEngine--&gt;Rule: Association(연관)
      BusinessRuleEngine--&gt;Facts: Association(연관)
      DefaultRule--&gt;Condition: Association(연관)
      DefaultRule--&gt;Action: Association(연관)
      Action..&gt; Facts: ependency(의존)
      Condition ..&gt; Facts: Dependency(의존)
      DefaultRule ..&gt;	Facts : Dependency(의존)
      RuleBuilder--&gt;Condition: Association(연관)
      RuleBuilder..&gt;Action: Association(연관)
      class Rule{
          +perform(Facts facts)
      }
      class Action{
          + execute(Facts facts)
      }
      class Condition{
          +bool evaluate(Facts facts)
      }
      
      class RuleBuilder{
           -Condition condition

          +when(Condition condition)
          + Rule then(Action action)
      }
      class DefaultRule{
           -Condition condition
           -Action action

          +perform(Facts facts)
      }
      class Facts{
           -Map&lt;String, String&gt; facts

          +String getFact(String name)
          +addFact(String name, String value)
      }
      class BusinessRuleEngine{
           - List&lt;Rule&gt; rules;
           - Facts facts;

          +addRule(Rule rule)
          +run()
      }</code></pre>
</div></div>

복세편살

비즈니스 규칙 엔진이란?
비즈니스 규칙 엔진이란, 어떤 조건에 따라 액션을 유발하는 규칙이 있는 비즈니스 기능을 구현할 때 사용하는 프로그램이다. 
비즈니스 규칙 엔진의 요구사항은 크게 4가지로 나뉜다.
팩트 : 규칙이 확인할 수 있는 정보
액션 : 수행하려는 동작
조건 : 액션을 언제 발생시킬지 지정
규칙 : 실행하려는 비즈니스 규칙을 지정
보통 팩트/액션/조건을 한 그룹으로 묶어서 규칙으로 만든다.
비즈니스 규칙 엔진 구현 방법은 다음과 같다.
Diagram
Code
Class
@FunctionalInterface
public interface Action {
  void execute(Facts facts);
}
 
@FunctionalInterface
public interface Condition {
  boolean evaluate(Facts facts);
}
 
@FunctionalInterface 
interface Rule {
  void perform(Facts facts);
}
// @FunctionalInterface (함수형 인터페이스)란 1 개의 추상 메소드를 갖는 인터페이스를 말한다.
 
class DefaultRule implements Rule {
  private final Condition condition;
  private final Action action;
  public DefaultRule(final Condition condition, final Action action) {
    this.condition = condition;
    this.action = action;
  }
  @Override
  public void perform(Facts facts) {
    if(condition.evaluate(facts)) {
      action.execute(facts);
    }
  }
}
 
public class RuleBuilder {
  private Condition condition;
  private RuleBuilder(final Condition condition) {
    this.condition = condition;
  }
  public static RuleBuilder when(final Condition condition) {
    return new RuleBuilder(condition);
  }
  public Rule then(final Action action) {
    return new DefaultRule(condition, action);
  }
}
 
import java.util.HashMap;
import java.util.Map;
public class Facts {
  private final Map<String, String> facts = new HashMap<>();
  public String getFact(final String name) {
    return this.facts.get(name);
  }
  public void addFact(final String name, final String value) {
    this.facts.put(name, value);
  }
}
 
import java.util.ArrayList;
import java.util.List;
public class BusinessRuleEngine {
  private final List<Rule> rules;
  private final Facts facts;
  public BusinessRuleEngine(final Facts facts) {
    this.rules = new ArrayList<>();
    this.facts = facts;
  }
  public void addRule(final Rule rule) {
    this.rules.add(rule);
  }
  public void run() {
    this.rules.forEach(rule -> rule.perform(facts));
  }
}
 
Client
final Rule ruleSendEmailToSalesWhenCEO = RuleBuilder
        .when(facts -> "CEO".equals(facts.getFact("jobTitle")))
        .then(facts -> {
          var name = facts.getFact("name");
          Mailer.sendEmail("sales@company.com", "Relevant customer: " + name);
        });
        
final facts = new Facts();
facts.addFact("name", "김복세");
facts.addFact("jobTitle", "CEO");
final BusinessRuleEngine businessRuleEngine = new BusinessRuleEngine(facts);
businessRuleEngine.addRule(ruleSendEmailToSalesWhenCEO);
businessRuleEngine.run();
 
참고
실전 자바 소프트웨어 개발 5장. 비즈니스 규칙 엔진
https://github.com/sojeongw/real-world-software-development/tree/main/buisiness-rule-engine
https://sabarada.tistory.com/72
 classDiagram
      DefaultRule ..|>	Rule : Realization(실체화)
      BusinessRuleEngine-->Rule: Association(연관)
      BusinessRuleEngine-->Facts: Association(연관)
      DefaultRule-->Condition: Association(연관)
      DefaultRule-->Action: Association(연관)
      Action..> Facts: ependency(의존)
      Condition ..> Facts: Dependency(의존)
      DefaultRule ..>	Facts : Dependency(의존)
      RuleBuilder-->Condition: Association(연관)
      RuleBuilder..>Action: Association(연관)
      class Rule{
          +perform(Facts facts)
      }
      class Action{
          + execute(Facts facts)
      }
      class Condition{
          +bool evaluate(Facts facts)
      }
      
      class RuleBuilder{
           -Condition condition
          +when(Condition condition)
          + Rule then(Action action)
      }
      class DefaultRule{
           -Condition condition
           -Action action
          +perform(Facts facts)
      }
      class Facts{
           -Map<String, String> facts
          +String getFact(String name)
          +addFact(String name, String value)
      }
      class BusinessRuleEngine{
           - List<Rule> rules;
           - Facts facts;
          +addRule(Rule rule)
          +run()
      }

비즈니스 규칙 엔진

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