宜昌网站建设选择宜昌慧享互动,北新泾街道网站建设,自己服务器做网站服务器备案,微信小程序设计目录 概念理解实例和编码抽象出2条规则简单的规则引擎事实1的处理事实2的处理 easy-rules 规则的抽象和执行事实描述规则的抽象默认的规则 动态代理执行规则和动作规则的执行#xff1a;org.jeasy.rules.core.DefaultRulesEngine#doFirepublic class RuleProxy implements Inv… 目录 概念理解实例和编码抽象出2条规则简单的规则引擎事实1的处理事实2的处理 easy-rules 规则的抽象和执行事实描述规则的抽象默认的规则 动态代理执行规则和动作规则的执行org.jeasy.rules.core.DefaultRulesEngine#doFirepublic class RuleProxy implements InvocationHandler规则执行监听器 回顾规则执行和监听器的执行过程扩展 概念理解
描述一个简单的处理基于一堆现实情况运用规则引擎、经过处理得到对应的结果然后再据此做后续的事情。
fact: 事实已有的现实情况即输入信息rules: 规则集合由一系列规则组成可能有不同的规则排列rule: 规则包含基本的判断条件和条件符合要做的动作。condition: 规则的判定条件特定的判断逻辑 if elseaction: 规则判定符合后执行的动作
实例和编码
一句话描述 人提着包去酒店买酒需要判断是否成年人成年人才能购买酒商店据此卖你酒你买到了酒就装包里走人回家喝酒去。
接下来看easy-rules的定义和处理。
抽象出2条规则
Rule(name age-rule, description age-rule, priority 1)
public class AgeRule {Conditionpublic boolean isAdult(Fact(person) Person person) {return person.getAge() 18;}Actionpublic void setAdult(Fact(person) Person person) {person.setAdult(true);}
}package org.jeasy.rules.tutorials.shop;import org.jeasy.rules.annotation.Action;
import org.jeasy.rules.annotation.Condition;
import org.jeasy.rules.annotation.Fact;
import org.jeasy.rules.annotation.Rule;/*** author dingqi on 2023/5/26* since 1.0.0*/
Rule(name alcohol-rule, description alcohol-rule, priority 2)
public class AlcoholRule {Conditionpublic boolean shopRule(Fact(person) Person person) {return person.isAdult() true;}Actionpublic void shopReply(Fact(bag) Bag bag) {bag.setSuccess(true);bag.add(Vodka);}
}简单的规则引擎
// create a rule set
Rules rules new Rules();
rules.register(new AgeRule());
rules.register(new AlcoholRule());//create a default rules engine and fire rules on known facts
DefaultRulesEngine rulesEngine new DefaultRulesEngine();
事实1的处理
Facts facts new Facts();
Person tom new Person(Tom, 19);
facts.put(person, tom);
Bag bag new Bag();
facts.put(bag, bag);System.out.println(Tom: Hi! can I have some Vodka please?);
rulesEngine.fire(rules, facts);
System.out.println(Tom: bag is bag);输出Tom成年了买到了伏特加
Tom: Hi! can I have some Vodka please?
Tom: bag is Bag{successtrue, goods[Vodka]}事实2的处理
Person jack new Person(Jack, 10);
facts.put(person, jack);
Bag bag2 new Bag();
facts.put(bag, bag2);System.out.println(Jack: Hi! can I have some Vodka please?);
rulesEngine.fire(rules, facts);
System.out.println(Jack: bag is bag2);输出Jack未成年无功而返
Jack: Hi! can I have some Vodka please?
Jack: bag is Bag{successfalse, goods[]}easy-rules 规则的抽象和执行
事实描述
public class Facts implements IterableFact? {private final SetFact? facts new HashSet();
/*** A class representing a named fact. Facts have unique names within a {link Facts}* instance.* * param T type of the fact* author Mahmoud Ben Hassine*/
public class FactT {private final String name;private final T value;
事实简单就是key、value对 某个事实的名称和事实的属性特征以一切皆对象来看就是一个一个的对象组成了事实。只要在规则条件真正执行前能明确这些事实就行
规则的抽象
名称描述优先级执行Facts的的方法
见org.jeasy.rules.api.Rule接口 和基础实现类org.jeasy.rules.core.BasicRule
条件和动作注解
Inherited
Retention(RetentionPolicy.RUNTIME)
Target(ElementType.METHOD)
public interface Condition {}Inherited
Retention(RetentionPolicy.RUNTIME)
Target(ElementType.METHOD)
public interface Condition {}默认的规则
class DefaultRule extends BasicRule {private final Condition condition;private final ListAction actions;DefaultRule(String name, String description, int priority, Condition condition, ListAction actions) {super(name, description, priority);this.condition condition;this.actions actions;}Overridepublic boolean evaluate(Facts facts) {return condition.evaluate(facts);}Overridepublic void execute(Facts facts) throws Exception {for (Action action : actions) {action.execute(facts);}}}动态代理执行规则和动作
使用org.jeasy.rules.api.Rules添加规则时如下
org.jeasy.rules.api.Rules#register public void register(Object... rules) {Objects.requireNonNull(rules);for (Object rule : rules) {Objects.requireNonNull(rule);this.rules.add(RuleProxy.asRule(rule));}}使用org.jeasy.rules.annotation.Rule注解构造的规则是使用RuleProxy构造的
规则的执行org.jeasy.rules.core.DefaultRulesEngine#doFire
void doFire(Rules rules, Facts facts) {if (rules.isEmpty()) {LOGGER.warn(No rules registered! Nothing to apply);return;}logEngineParameters();log(rules);log(facts);LOGGER.debug(Rules evaluation started);for (Rule rule : rules) {final String name rule.getName();final int priority rule.getPriority();if (priority parameters.getPriorityThreshold()) {LOGGER.debug(Rule priority threshold ({}) exceeded at rule {} with priority{}, next rules will be skipped,parameters.getPriorityThreshold(), name, priority);break;}if (!shouldBeEvaluated(rule, facts)) {LOGGER.debug(Rule {} has been skipped before being evaluated, name);continue;}boolean evaluationResult false;try {evaluationResult rule.evaluate(facts);} catch (RuntimeException exception) {LOGGER.error(Rule name evaluated with error, exception);triggerListenersOnEvaluationError(rule, facts, exception);// give the option to either skip next rules on evaluation error or continue by considering the evaluation error as falseif (parameters.isSkipOnFirstNonTriggeredRule()) {LOGGER.debug(Next rules will be skipped since parameter skipOnFirstNonTriggeredRule is set);break;}}if (evaluationResult) {LOGGER.debug(Rule {} triggered, name);triggerListenersAfterEvaluate(rule, facts, true);try {triggerListenersBeforeExecute(rule, facts);rule.execute(facts);LOGGER.debug(Rule {} performed successfully, name);triggerListenersOnSuccess(rule, facts);if (parameters.isSkipOnFirstAppliedRule()) {LOGGER.debug(Next rules will be skipped since parameter skipOnFirstAppliedRule is set);break;}} catch (Exception exception) {LOGGER.error(Rule name performed with error, exception);triggerListenersOnFailure(rule, exception, facts);if (parameters.isSkipOnFirstFailedRule()) {LOGGER.debug(Next rules will be skipped since parameter skipOnFirstFailedRule is set);break;}}} else {LOGGER.debug(Rule {} has been evaluated to false, it has not been executed, name);triggerListenersAfterEvaluate(rule, facts, false);if (parameters.isSkipOnFirstNonTriggeredRule()) {LOGGER.debug(Next rules will be skipped since parameter skipOnFirstNonTriggeredRule is set);break;}}}
}默认的规则引擎直接遍历规则去执行如果condition执行命中后则去执行action
public class RuleProxy implements InvocationHandler private Object evaluateMethod(final Object[] args) throws IllegalAccessException, InvocationTargetException {Facts facts (Facts) args[0];Method conditionMethod getConditionMethod();try {ListObject actualParameters getActualParameters(conditionMethod, facts);return conditionMethod.invoke(target, actualParameters.toArray()); // validated upfront} catch (NoSuchFactException e) {LOGGER.warn(Rule {} has been evaluated to false due to a declared but missing fact {} in {},getTargetClass().getName(), e.getMissingFact(), facts);return false;} catch (IllegalArgumentException e) {LOGGER.warn(Types of injected facts in method {} in rule {} do not match parameters types,conditionMethod.getName(), getTargetClass().getName(), e);return false;}
}规则执行监听器
在规则执行的过程中可以做各种操作。可以看成规则的扩展点
/*** A listener for rule execution events.** author Mahmoud Ben Hassine (mahmoud.benhassineicloud.com)*/
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) { }}回顾规则执行和监听器的执行过程
// 1. 条件执行前
triggerListenersBeforeEvaluate(rule, facts);
try {evaluationResult rule.evaluate(facts);
} catch(Exception e){// 2. 条件执行失败triggerListenersOnEvaluationError(rule, facts, exception);
}if (evaluationResult) {// 3. 条件执行后条件满足triggerListenersAfterEvaluate(rule, facts, true);try {// 4. 动作执行前triggerListenersBeforeExecute(rule, facts);rule.execute(facts);// 5. 动作执行后triggerListenersOnSuccess(rule, facts);} catch (Exception exception) {// 6. 条件执行失败triggerListenersOnFailure(rule, exception, facts);}
}else{// 3. 条件执行后条件不满足triggerListenersAfterEvaluate(rule, facts, false);
}扩展
Java Expression Language (JEXL) 表达式语言引擎
https://commons.apache.org/proper/commons-jexl/apidocs/org/apache/commons/jexl3/JexlEngine.html MVEL一个功能强大的基于Java应用程序的表达式语言。 SpELSpring表达式语言
name: adult rule
description: when age is greater than 18, then mark as adult
priority: 1
condition: #{ [person].age 18 }
actions:- #{ [person].setAdult(true) }
