Drools决策表实践运用

决策表使用方式
在Drools中，决策表通常是以Excel（.xls或.xlsx）或者CSV格式存储的，这些格式的决策表并不能直接被Drools执行。它们需要被转换成Drools规则语言（DRL）的文本格式，之后才能被编译和执行。Drools提供了工具来帮助完成这一转换，主要使用org.drools.decisiontable.SpreadsheetCompiler类，以下是一个基本的转换过程
这是我的决策表：表一（ Pricing bracket）

表二(Discounts)

文件名称：ExamplePolicyPricing.xls，的结构目录：

     // 加载决策表文件InputStream is = DecisionTableToDRL.class.getResourceAsStream("/path/to/decisiontable.xls");// 创建SpreadsheetCompiler实例SpreadsheetCompiler compiler = SpreadsheetCompilerFactory.newCompiler();// 转换决策表为DRLString drl = compiler.compile(is, "UTF-8", "decisiontable");// 打印DRL规则System.out.println(drl);

xls转为drl结果为：

package com.mk.examples.decisiontable;
//generated from Decision Table
import com.mking.drools.bean.decisiontable.*;
// rule values at B9, header at B4
rule "Pricing bracket_9"
whenDriver(age >= 18, age <= 24, locationRiskProfile == "LOW", priorClaims == "1")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.setBasePrice(450);
end// rule values at B10, header at B4
rule "Pricing bracket_10"
whenDriver(age >= 18, age <= 24, locationRiskProfile == "MED")policy: Policy(type == "FIRE_THEFT")
thenpolicy.setBasePrice(200);System.out.println("Priors not relevant");
end// rule values at B11, header at B4
rule "Pricing bracket_11"
whenDriver(age >= 18, age <= 24, locationRiskProfile == "MED", priorClaims == "0")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.setBasePrice(300);
end// rule values at B12, header at B4
rule "Pricing bracket_12"
whenDriver(age >= 18, age <= 24, locationRiskProfile == "LOW")policy: Policy(type == "FIRE_THEFT")
thenpolicy.setBasePrice(150);
end// rule values at B13, header at B4
rule "Pricing bracket_13"
whenDriver(age >= 18, age <= 24, locationRiskProfile == "LOW", priorClaims == "0")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.setBasePrice(150);System.out.println("Safe driver discount");
end// rule values at B14, header at B4
rule "Pricing bracket_14"
whenDriver(age >= 18, age <= 24, locationRiskProfile == "MED", priorClaims == "1")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.setBasePrice(700);
end// rule values at B15, header at B4
rule "Pricing bracket_15"
whenDriver(age >= 18, age <= 24, locationRiskProfile == "HIGH", priorClaims == "0")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.setBasePrice(700);System.out.println("Location risk");
end// rule values at B16, header at B4
rule "Pricing bracket_16"
whenDriver(age >= 18, age <= 24, locationRiskProfile == "HIGH")policy: Policy(type == "FIRE_THEFT")
thenpolicy.setBasePrice(550);System.out.println("Location risk");
end// rule values at B17, header at B4
rule "Pricing bracket_17"
whenDriver(age >= 25, age <= 30, priorClaims == "0")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.setBasePrice(120);System.out.println("Cheapest possible");
end// rule values at B18, header at B4
rule "Pricing bracket_18"
whenDriver(age >= 25, age <= 30, priorClaims == "1")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.setBasePrice(300);
end// rule values at B19, header at B4
rule "Pricing bracket_19"
whenDriver(age >= 25, age <= 30, priorClaims == "2")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.setBasePrice(590);
end// rule values at B20, header at B4
rule "Pricing bracket_20"
whenDriver(age >= 25, age <= 35, priorClaims == "3")policy: Policy(type == "THIRD_PARTY")
thenpolicy.setBasePrice(800);System.out.println("High risk");
end// rule values at B27, header at B22
rule "Discounts_27"
whenDriver(age >= 20, age <= 24, priorClaims == "0")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.applyDiscount(1);
end// rule values at B28, header at B22
rule "Discounts_28"
whenDriver(age >= 18, age <= 24, priorClaims == "0")policy: Policy(type == "FIRE_THEFT")
thenpolicy.applyDiscount(2);
end// rule values at B29, header at B22
rule "Discounts_29"
whenDriver(age >= 25, age <= 30, priorClaims == "1")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.applyDiscount(5);
end// rule values at B30, header at B22
rule "Discounts_30"
whenDriver(age >= 25, age <= 30, priorClaims == "2")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.applyDiscount(1);
end// rule values at B31, header at B22
rule "Discounts_31"
whenDriver(age >= 25, age <= 30, priorClaims == "0")policy: Policy(type == "COMPREHENSIVE")
thenpolicy.applyDiscount(20);
end

执行drl代码及结果

动态加载drl可以参考该文：Drools实践与动态加载
以下是drl解析过程：

 KieHelper kieHelper = new KieHelper();
kieHelper.addContent(drl, ResourceType.DRL);KieSession ksession = kieHelper.build().newKieSession();
Driver def = new Driver();
Policy policy = new Policy();
ksession.insert(def);
ksession.insert(policy);
int count = ksession.fireAllRules();
ksession.dispose();

总结：决策表其实就是Excel转化为DRL文件的过程