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关于Drools规则引擎的实践经验与封装

前言

Drools规则引擎在开发中应用广泛，但由于其复杂性，许多开发者在实际项目中未能充分发挥其潜力。本文作者经过两次项目实践，总结了对Drools的理解，并进行了封装，旨在简化规则引擎的使用和管理，同时探讨如何高效获取和使用规则内容。

设计思路与具体实现

为了实现轻量级的Drools使用，我们遵循以下设计理念：保持架构简洁，便于与其他项目无缝融合。具体实现包括规则的动态获取、远程管理和灵活配置。

动态规则管理

我们设计了一个工具类DroolsUtils，支持从本地规则文件和远程仓库中动态获取规则内容。通过Maven和Drools6.5提供的API，实现了对规则资源的灵活管理和版本控制。

工具类实现详解

下面是DroolsUtils工具类的核心功能解析：

package com.vip.jie.rule.util;
import org.drools.compiler.kie.builder.impl.InternalKieModule;
import org.kie.api.KieServices;
import org.kie.api.builder.KieBuilder;
import org.kie.api.builder.KieFileSystem;
import org.kie.api.builder.ReleaseId;
import org.kie.api.builder.model.KieBaseModel;
import org.kie.api.builder.model.KieModuleModel;
import org.kie.api.builder.model.KieSessionModel;
import org.kie.api.conf.EqualityBehaviorOption;
import org.kie.api.conf.EventProcessingOption;
import java.io.IOException;
public class DroolsUtils {
    private static KieFileSystem createKieFileSystemWithKProject(KieServices ks, boolean isdefault) {
        KieModuleModel kproj = ks.newKieModuleModel();
        KieBaseModel kieBaseModel1 = kproj.newKieBaseModel("KBase").setDefault(isdefault)
                .setEqualsBehavior(EqualityBehaviorOption.EQUALITY)
                .setEventProcessingMode(EventProcessingOption.STREAM);
        // 配置KieSession
        kieBaseModel1.newKieSessionModel("KSession").setDefault(isdefault)
                .setType(KieSessionModel.KieSessionType.STATEFUL);
        KieFileSystem kfs = ks.newKieFileSystem();
        kfs.writeKModuleXML(kproj.toXML());
        return kfs;
    }
    private static String getPom(ReleaseId releaseId, ReleaseId... dependencies) {
        String pom = "
   "
                + "
   
    "
                + "    
    
     4.0.0
    "
                + "    
    
     " + releaseId.getGroupId() + "
    "
                + "    
    
     " + releaseId.getArtifactId() + "
    "
                + "    
    
     " + releaseId.getVersion() + "
    ";
        if (dependencies != null && dependencies.length > 0) {
            for (ReleaseId dep : dependencies) {
                pom += "    < dependency>"
                        + "      
    
     " + dep.getGroupId() + "
    "
                        + "      
    
     " + dep.getArtifactId() + "
    "
                        + "      
    
     " + dep.getVersion() + "
    "
                        + "    
    ";
            }
        }
        return pom;
    }
    public static InternalKieModule createKieJar(KieServices ks, ReleaseId releaseId, DroolsResource droolsResource)
            throws IOException {
        KieFileSystem kfs = createKieFileSystemWithKProject(ks, true);
        kfs.writePomXML(getPom(releaseId));
        kfs.write("src/main/resources/" + droolsResource.getTargetResourceName(), droolsResource.getResource());
        KieBuilder kieBuilder = ks.newKieBuilder(kfs);
        if (!kieBuilder.getResults().getMessages().isEmpty()) {
            throw new IllegalStateException("Error creating KieBuilder. errorMsg:" + kieBuilder.getResults().getMessages());
        }
        return (InternalKieModule) kieBuilder.getKieModule();
    }
}
   

实际应用示例

单元测试类

package com.vip.jie.rule.service.impl;
import com.vip.jie.rule.object.User;
import com.vip.jie.rule.service.RuleManager;
import lombok.extern.slf4j.Slf4j;
import org.junit.Test;
import static junit.framework.TestCase.fail;
import org.kie.api.rulemanager.RuleManager;
@Slf4j
public class RuleManagerImplTest {
    private RuleManager ruleManager = new RuleManagerImpl();
    private String getRuleContent() {
        StringBuilder stringBuilder = new StringBuilder();
        stringBuilder.append("import com.vip.jie.rule.object.User;\n");
        stringBuilder.append("rule test1 when\n");
        stringBuilder.append("user : User(age==20)\n");
        stringBuilder.append("then\n");
        stringBuilder.append("user.setName(\"张三\");\n");
        stringBuilder.append("end\n");
        return stringBuilder.toString();
    }
    @Test
    public void executeRule1() throws Exception {
        User user = new User();
        user.setAge(20);
        ruleManager.executeRule("test1", getRuleContent(), user);
        log.info("test result:{}", user.toString());
        if (!"张三".equals(user.getName())) {
            fail("error rule");
        }
    }
    @Test
    public void executeRule2() throws Exception {
        User user = new User();
        user.setAge(21);
        ruleManager.executeRule("test1", getRuleContent(), user);
        log.info("test result:{}", user.toString());
        if ("张三".equals(user.getName())) {
            fail("error rule");
        }
    }
}

工具类应用示例

String fileName = "jie-" + group + "-rules";
ReleaseId releaseId = kieServices.newReleaseId("com.vip.jie", fileName, "1.0.0");
log.info("DroolsGetKieSession fileName:{}", fileName);
log.info("[DroolsGetKieSession] drlStr:{}", drlStr);
InternalKieModule kJar = DroolsUtils.createKieJar(kieServices, releaseId, new DroolsResource(
    ResourceFactory.newByteArrayResource(drlStr.getBytes()),
    fileName + ".drl"
));

进一步优化与扩展

我们还计划在以下方面进行优化与扩展：

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