java开源引擎easyrule_规则引擎及easyrules机制分析
一、什么是规则引擎
最近在工作中，遇到一类上层业务规则多变的场景。所以研究了规则引擎相关的内容，在这里可以与大家一起探讨。规则引擎相关的概念和相关业内使用，可以参考以下两篇文章，分析的很到位，也指出了大体的方向和具体的实践：
二、规则引擎实践
规则引擎的实现有比较多的开源组件，比较出名的是Drools，属于重量级的实现。本文主要介绍一款轻量级的规则引擎实现：easyrules
1、什么是EasyRules？
You can build a simple rules engine yourself. All you need is to create a bunch of objects with conditions and actions, store them in a collection, and run through them to evaluate the conditions and execute the actions.
2、框架特点
轻量级类库和容易上手
基于POJO的开发与注解的编程模型
方便且适用于java的抽象的业务模型规则
支持从简单的规则创建组合规则
Useful abstractions to define business rules and apply them easily with Java
The ability to create composite rules from primitive ones
3、实践-FizzBuzz
循环打印 1 到 100，但如果是 5 的倍數就印 fizz，如果是 7 的倍數就印 buzz，如果同時是 5 和 7 的倍數就印 fizzzuzz,否则打印数字本身
不使用规则引擎
@Test
public void fizzbuzz() {
for(int i = 1; i <= 100; i++) {
if (((i % 5) == 0) && ((i % 7) == 0))
System.out.print("fizzbuzz");
else if ((i % 5) == 0) System.out.print("fizz");
else if ((i % 7) == 0) System.out.print("buzz");
else System.out.print(i);
System.out.println();
}
System.out.println();
}
使用Easy Rule
定义FizzRule
检查输入是否是fizz
@Rule
public class FizzRule {
private int input;
@Condition
public boolean isFizz() {
return input % 5 == 0;
}
@Action
public void printFizz() {
System.out.print("fizz");
}
public void setInput(int input) {
this.input = input;
}
@Priority
public int getPriority() {
return 1;
}
}
BuzzRule
检查输入是否是buzz
@Rule
public class BuzzRule {
private int input;
@Condition
public boolean isBuzz() {
return input % 7 == 0;
}
@Action
public void printBuzz() {
System.out.print("buzz");
}
public void setInput(int input) {
this.input = input;
}
@Priority
public int getPriority() {
return 2;
}
}
FizzBuzzRule
检查输入是否是fizzbuzz，这是一个组合规则，它由FizzRule和BuzzRule组成
public class FizzBuzzRule extends CompositeRule {
public FizzBuzzRule(Object... rules) {
for (Object rule : rules) {
addRule(rule);
}
}
@Override
public int getPriority() {
return 0;
}
}
NonFizzBuzzRule
@Rule
public class NonFizzBuzzRule {
private int input;
@Condition
public boolean isNotFizzNorBuzz() {
// can return true here
return input % 5 != 0 || input % 7 != 0;
}
@Action
public void printInput() {
System.out.print(input);
}
public void setInput(int input) {
this.input = input;
}
@Priority
public int getPriority() {
return 3;
}
}
执行
public class FizzBuzzWithEasyRules {
public static void main(String[] args) {
// create rules engine
RulesEngine fizzBuzzEngine =
RulesEngineBuilder.aNewRulesEngine()
.withSkipOnFirstAppliedRule(true) // 如果第一个规则满足条件，后面的规则将不再执行
.withSilentMode(true)
.build();
// create rules
FizzRule fizzRule = new FizzRule();
BuzzRule buzzRule = new BuzzRule();
FizzBuzzRule fizzBuzzRule
= new FizzBuzzRule(fizzRule, buzzRule);
NonFizzBuzzRule nonFizzBuzzRule = new NonFizzBuzzRule();
// register rules
fizzBuzzEngine.registerRule(fizzRule);
fizzBuzzEngine.registerRule(buzzRule);
fizzBuzzEngine.registerRule(fizzBuzzRule);
fizzBuzzEngine.registerRule(nonFizzBuzzRule);
// fire rules
for (int i = 1; i <= 100; i++) {
fizzRule.setInput(i);
buzzRule.setInput(i);
nonFizzBuzzRule.setInput(i);
fizzBuzzEngine.fireRules();
System.out.println();
}
}
}
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