Java规则引擎Easy Rules的使用介绍

 @Rule(name = "weather rule", description = "if it rains then take an umbrella") public class WeatherRule { @Condition public boolean itRains(@Fact("rain") boolean rain) { return rain; } @Action public void takeAnUmbrella() { System.out.println("It rains, take an umbrella!"); } }

 Rule weatherRule = new RuleBuilder() .name("weather rule") .description("if it rains then take an umbrella") .when(facts -> facts.get("rain").equals(true)) .then(facts -> System.out.println("It rains, take an umbrella!")) .build();

 Rule weatherRule = new MVELRule() .name("weather rule") .description("if it rains then take an umbrella") .when("rain == true") .then("System.out.println(\"It rains, take an umbrella!\");");

 name: "weather rule" description: "if it rains then take an umbrella" condition: "rain == true" actions: - "System.out.println(\"It rains, take an umbrella!\");"

 MVELRuleFactory ruleFactory = new MVELRuleFactory(new YamlRuleDefinitionReader()); Rule weatherRule = ruleFactory.createRule(new FileReader("weather-rule.yml"));

 public class Test { public static void main(String[] args) { // define facts Facts facts = new Facts(); facts.put("rain", true); // define rules Rule weatherRule = ... Rules rules = new Rules(); rules.register(weatherRule); // fire rules on known facts RulesEngine rulesEngine = new DefaultRulesEngine(); rulesEngine.fire(rules, facts); } }

  org.jeasyeasy-rules-core4.0.0

 mvn archetype:generate \ -DarchetypeGroupId=org.jeasy \ -DarchetypeArtifactId=easy-rules-archetype \ -DarchetypeVersion=4.0.0

 package com.cjs.example.rules; import org.jeasy.rules.annotation.Action; import org.jeasy.rules.annotation.Condition; import org.jeasy.rules.annotation.Rule; @Rule(name = "Hello World rule", description = "Always say hello world") public class HelloWorldRule { @Condition public boolean when() { return true; } @Action public void then() throws Exception { System.out.println("hello world"); } }

 public interface Rule { /** * This method encapsulates the rule's conditions. * @return true if the rule should be applied given the provided facts, false otherwise */ boolean evaluate(Facts facts); /** * This method encapsulates the rule's actions. * @throws Exception if an error occurs during actions performing */ void execute(Facts facts) throws Exception; //Getters and setters for rule name, description and priority omitted. }

 @Rule(name = "my rule", description = "my rule description", priority = 1) public class MyRule { @Condition public boolean when(@Fact("fact") fact) { //my rule conditions return true; } @Action(order = 1) public void then(Facts facts) throws Exception { //my actions } @Action(order = 2) public void finally() throws Exception { //my final actions } }

 Rule rule = new RuleBuilder() .name("myRule") .description("myRuleDescription") .priority(3) .when(condition) .then(action1) .then(action2) .build();

 //Create a composite rule from two primitive rules UnitRuleGroup myUnitRuleGroup = new UnitRuleGroup("myUnitRuleGroup", "unit of myRule1 and myRule2"); myUnitRuleGroup.addRule(myRule1); myUnitRuleGroup.addRule(myRule2); //Register the composite rule as a regular rule Rules rules = new Rules(); rules.register(myUnitRuleGroup); RulesEngine rulesEngine = new DefaultRulesEngine(); rulesEngine.fire(rules, someFacts);

 public class Fact { private final String name; private final T value; }

 Fact fact = new Fact("foo", "bar"); Facts facts = new Facts(); facts.add(fact);

 Facts facts = new Facts(); facts.put("foo", "bar");

 @Rule class WeatherRule { @Condition public boolean itRains(@Fact("rain") boolean rain) { return rain; } @Action public void takeAnUmbrella(Facts facts) { System.out.println("It rains, take an umbrella!"); // can add/remove/modify facts } }

 RulesEngine rulesEngine = new DefaultRulesEngine(); // or RulesEngine rulesEngine = new InferenceRulesEngine();

 rulesEngine.fire(rules, facts);

 RulesEngineParameters parameters = new RulesEngineParameters() .rulePriorityThreshold(10) .skipOnFirstAppliedRule(true) .skipOnFirstFailedRule(true) .skipOnFirstNonTriggeredRule(true); RulesEngine rulesEngine = new DefaultRulesEngine(parameters);

 public interface RuleListener { /** * Triggered before the evaluation of a rule. * * @param rule being evaluated * @param facts known before evaluating the rule * @return true if the rule should be evaluated, false otherwise */ default boolean beforeEvaluate(Rule rule, Facts facts) { return true; } /** * Triggered after the evaluation of a rule. * * @param rule that has been evaluated * @param facts known after evaluating the rule * @param evaluationResult true if the rule evaluated to true, false otherwise */ default void afterEvaluate(Rule rule, Facts facts, boolean evaluationResult) { } /** * Triggered on condition evaluation error due to any runtime exception. * * @param rule that has been evaluated * @param facts known while evaluating the rule * @param exception that happened while attempting to evaluate the condition. */ default void onEvaluationError(Rule rule, Facts facts, Exception exception) { } /** * Triggered before the execution of a rule. * * @param rule the current rule * @param facts known facts before executing the rule */ default void beforeExecute(Rule rule, Facts facts) { } /** * Triggered after a rule has been executed successfully. * * @param rule the current rule * @param facts known facts after executing the rule */ default void onSuccess(Rule rule, Facts facts) { } /** * Triggered after a rule has failed. * * @param rule the current rule * @param facts known facts after executing the rule * @param exception the exception thrown when attempting to execute the rule */ default void onFailure(Rule rule, Facts facts, Exception exception) { } }

  4.0.0com.cjs.exampleeasy-rules-quickstart1.0.0-SNAPSHOTjar  org.jeasyeasy-rules-core4.0.0 org.jeasyeasy-rules-support4.0.0 org.jeasyeasy-rules-mvel4.0.0 org.slf4jslf4j-simple1.7.30