RuleBook <img src="https://github.com/Clayton7510/RuleBook/blob/master/LambdaBook.png" height="100" align="left"/>

» A Simple & Intuitive Rules Abstraction for Java <br/>_{100% Java · Lambda Enabled · Simple, Intuitive DSL · Lightweight}

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Why RuleBook?

RuleBook rules are built in the way that Java developers think: Java code. And they are executed in the way that programmers expect: In order. RuleBook also allows you to specify rules using an easy to use Lambda enabled Domain Specific Language or using POJOs that you define!

Tired of classes filled with if/then/else statements? Need a nice abstraction that allows rules to be easily specified in a way that decouples them from each other? Want to write rules the same way that you write the rest of your code [in Java]? RuleBook just might be the rules abstraction you've been waiting for!

<sub>Got questions? Here are answers to Frequently Asked Questions!<sub>

_{Still not finding what you are looking for? Try the Wiki!}

Contents

• 1 Getting RuleBook
  • 1.1 Building RuleBook
  • 1.2 Maven Central Releases
  • 1.3 Latest SNAPSHOT Releases
  • 1.4 Adding RuleBook to Your Maven Project
  • 1.5 Adding RuleBook to Your Gradle Project
• 2 Using RuleBook
  • 2.1 A Hello World Example
  • 2.2 An Example Using Facts
  • 2.3 A [Slightly] More Complex Scenario
  • 2.4 Thread Safety
• 3 The RuleBook Domain Specific Language
  • 3.1 Given-When-Then: The Basis of the RuleBook Language
  • 3.2 The Using Method
  • 3.3 The Stop Method
  • 3.4 Working With Facts
    • 3.4.1 The Single Fact Convenience Method
    • 3.4.2 The FactMap Convenience Methods
  • 3.5 Auditing Rules
  • 3.6 Rule Chain Behavior
• 4 POJO Rules
  • 4.1 A POJO Rules Example
  • 4.2 A [Slightly] More Complex POJO Rules Example
  • 4.3 POJO Rules Explained
    • 4.3.1 Ordering POJO Rules
    • 4.3.2 Injecting Collections into POJO Rules
    • 4.3.3 POJO Rule Annotation Inheritance
    • 4.3.4 Auditing POJO Rules
    • 4.3.5 POJO Rule Chain Behavior
• 5 Using RuleBook with Spring
  • 5.1 Adding RuleBook Spring Support to Your Project
  • 5.2 Creating Spring Enabled POJO Rules
  • 5.3 Configuring a RuleBook in Spring
  • 5.4 Using a Spring Enabled RuleBook
  • 5.5 Ordering Rules With Spring
• 6 How to Contribute
  • 6.1 Developer Guidelines

1 Getting RuleBook

1.1 Building RuleBook

git clone https://github.com/Clayton7510/RuleBook.git
cd RuleBook
./gradlew build

1.2 Maven Central Releases

• rulebook-core    
• rulebook-spring

1.3 Latest Sonatype SNAPSHOT (Development) Release

• rulebook-core    
• rulebook-spring

1.4 Adding RuleBook to Your Maven Project

Add the code below to your pom.xml

<dependency>
    <groupId>com.deliveredtechnologies</groupId>
    <artifactId>rulebook-core</artifactId>
    <version>0.12</version>
</dependency>

1.5 Adding RuleBook to Your Gradle Project

Add the code below to your build.gradle

compile 'com.deliveredtechnologies:rulebook-core:0.12'

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2 Using RuleBook

2.1 A HelloWorld Example

RuleBook ruleBook = RuleBookBuilder.create()
    .addRule(rule -> rule.withNoSpecifiedFactType()
      .then(f -> System.out.print("Hello "))
      .then(f -> System.out.println("World")))
    .build();

...or use 2 rules

RuleBook ruleBook = RuleBookBuilder.create()
    .addRule(rule -> rule.withNoSpecifiedFactType().then(f -> System.out.print("Hello ")))
    .addRule(rule -> rule.withNoSpecifiedFactType().then(f -> System.out.println("World")))
    .build();

now, run it!

ruleBook.run(new FactMap());

2.2 The Above Example Using Facts

RuleBook ruleBook = RuleBookBuilder.create()
    .addRule(rule -> rule.withFactType(String.class)
      .when(f -> f.containsKey("hello"))
      .using("hello")
      .then(System.out::print))
    .addRule(rule -> rule.withFactType(String.class)
      .when(f -> f.containsKey("world"))
      .using("world")
      .then(System.out::println))
    .build();

..or it could be a single rule

RuleBook ruleBook = RuleBookBuilder.create()
  .addRule(rule -> rule.withFactType(String.class)
    .when(f -> f.containsKey("hello") && f.containsKey("world"))
    .using("hello").then(System.out::print)
    .using("world").then(System.out::println))
  .build();

now, run it!

NameValueReferableMap factMap = new FactMap();
factMap.setValue("hello", "Hello ");
factMap.setValue("world", " World");
ruleBook.run(factMap);

2.3 A [Slightly] More Complex Scenario

MegaBank issues home loans. If an applicant's credit score is less than 600 then they must pay 4x the current rate. If an applicant’s credit score is between 600, but less than 700, then they must pay a an additional point on top of their rate. If an applicant’s credit score is at least 700 and they have at least $25,000 cash on hand, then they get a quarter point reduction on their rate. If an applicant is a first time home buyer then they get a 20% reduction on their calculated rate after adjustments are made based on credit score (note: first time home buyer discount is only available for applicants with a 600 credit score or greater).

public class ApplicantBean {
  private int creditScore;
  private double cashOnHand;
  private boolean firstTimeHomeBuyer;

  public ApplicantBean(int creditScore, double cashOnHand, boolean firstTimeHomeBuyer) {
    this.creditScore = creditScore;
    this.cashOnHand = cashOnHand;
    this.firstTimeHomeBuyer = firstTimeHomeBuyer;
  }

  public int getCreditScore() {
    return creditScore;
  }

  public void setCreditScore(int creditScore) {     
    this.creditScore = creditScore;
  }

  public double getCashOnHand() {
    return cashOnHand;
  }

  public void setCashOnHand(double cashOnHand) {
    this.cashOnHand = cashOnHand;
  }

  public boolean isFirstTimeHomeBuyer() {
    return firstTimeHomeBuyer;
  }

  public void setFirstTimeHomeBuyer(boolean firstTimeHomeBuyer) {
    this.firstTimeHomeBuyer = firstTimeHomeBuyer;
  }
}

public class HomeLoanRateRuleBook extends CoRRuleBook<Double> {
  @Override
  public void defineRules() {
    //credit score under 600 gets a 4x rate increase
    addRule(RuleBuilder.create().withFactType(ApplicantBean.class).withResultType(Double.class)
      .when(facts -> facts.getOne().getCreditScore() < 600)
      .then((facts, result) -> result.setValue(result.getValue() * 4))
      .stop()
      .build());

    //credit score between 600 and 700 pays a 1 point increase
    addRule(RuleBuilder.create().withFactType(ApplicantBean.class).withResultType(Double.class)
      .when(facts -> facts.getOne().getCreditScore() < 700)
      .then((facts, result) -> result.setValue(result.getValue() + 1))
      .build());

    //credit score is 700 and they have at least $25,000 cash on hand
    addRule(RuleBuilder.create().withFactT