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Introduction to Drools Engine

1. Basic Introduction

2. Rule grammar

(1) Demonstration drl file format

package droolRule ;
import org.slf4j.Logger
import org.slf4j.LoggerFactory ;
dialect  "java"
rule "paramcheck1"
    when 
    then
        final Logger LOGGER = LoggerFactory.getLogger("param-check-one Rule engine") ;
        LOGGER.info("parameter");
end

(2) Grammatical Explanation

· File format
 It can be.drl, xml file or hard block of Java code block.
· package
 In a rule file, the package must be defined and placed in the first line of the rule file.
· import
 The external variables used in the rule file can be either a class or an accessible static method in the class.
· rule
 Define a rule. paramcheck1 rule name. Rules usually include three parts: attributes, conditions and results.

Integrating SpringBook Framework

1. Project structure

2. Core Dependence

<!--drools Rule engine-->
<dependency>
    <groupId>org.drools</groupId>
    <artifactId>drools-core</artifactId>
    <version>7.6.0.Final</version>
</dependency>
<dependency>
    <groupId>org.drools</groupId>
    <artifactId>drools-compiler</artifactId>
    <version>7.6.0.Final</version>
</dependency>
<dependency>
    <groupId>org.drools</groupId>
    <artifactId>drools-templates</artifactId>
    <version>7.6.0.Final</version>
</dependency>
<dependency>
    <groupId>org.kie</groupId>
    <artifactId>kie-api</artifactId>
    <version>7.6.0.Final</version>
</dependency>
<dependency>
    <groupId>org.kie</groupId>
    <artifactId>kie-spring</artifactId>
    <version>7.6.0.Final</version>
</dependency>

3. Configuration file

@Configuration
public class RuleEngineConfig {
    private static final Logger LOGGER = LoggerFactory.getLogger(RuleEngineConfig.class) ;
    private static final String RULES_PATH = "droolRule/";
    private final KieServices kieServices = KieServices.Factory.get();
    @Bean
    public KieFileSystem kieFileSystem() throws IOException {
        KieFileSystem kieFileSystem = kieServices.newKieFileSystem();
        ResourcePatternResolver resourcePatternResolver = new PathMatchingResourcePatternResolver();
        Resource[] files = resourcePatternResolver.getResources("classpath*:" + RULES_PATH + "*.*");
        String path = null;
        for (Resource file : files) {
            path = RULES_PATH + file.getFilename();
            LOGGER.info("path="+path);
            kieFileSystem.write(ResourceFactory.newClassPathResource(path, "UTF-8"));
        }
        return kieFileSystem;
    }
    @Bean
    public KieContainer kieContainer() throws IOException {
        KieRepository kieRepository = kieServices.getRepository();
        kieRepository.addKieModule(kieRepository::getDefaultReleaseId);
        KieBuilder kieBuilder = kieServices.newKieBuilder(kieFileSystem());
        kieBuilder.buildAll();
        return kieServices.newKieContainer(kieRepository.getDefaultReleaseId());
    }
    @Bean
    public KieBase kieBase() throws IOException {
        return kieContainer().getKieBase();
    }
    @Bean
    public KieSession kieSession() throws IOException {
        return kieContainer().newKieSession();
    }
    @Bean
    public KModuleBeanFactoryPostProcessor kiePostProcessor() {
        return new KModuleBeanFactoryPostProcessor();
    }
}

This completes environmental integration.

3. Demonstration cases

1. Rule Documents

• Rule 1

dialect  "java"
rule "paramcheck1"
    salience 99
    when queryParam : QueryParam(paramId != null && paramSign.equals("+"))
        resultParam : RuleResult()
    then
        final Logger LOGGER = LoggerFactory.getLogger("param-check-one Rule engine") ;
        LOGGER.info("parameter:getParamId="+queryParam.getParamId()+";getParamSign="+queryParam.getParamSign());
        RuleEngineServiceImpl ruleEngineService = new RuleEngineServiceImpl() ;
        ruleEngineService.executeAddRule(queryParam);
        resultParam.setPostCodeResult(true);
end

• Rule two

dialect  "java"
rule "paramcheck2"
    salience 88
    when queryParam : QueryParam(paramId != null && paramSign.equals("-"))
        resultParam : RuleResult()
    then
        final Logger LOGGER = LoggerFactory.getLogger("param-check-two Rule engine") ;
        LOGGER.info("parameter:getParamId="+queryParam.getParamId()+";getParamSign="+queryParam.getParamSign());
        RuleEngineServiceImpl ruleEngineService = new RuleEngineServiceImpl() ;
        ruleEngineService.executeRemoveRule(queryParam);
        resultParam.setPostCodeResult(true);
end

Rule Description:

A. The bigger the value of salience, the higher the priority of execution.

B. Rule flow: If paramId is not null, the parameter identifier is + number, add rules, - number, remove rules.

2. Rule Execution Code

@Service
public class RuleEngineServiceImpl implements RuleEngineService {
    private static final Logger LOGGER = LoggerFactory.getLogger(RuleEngineServiceImpl.class) ;
    @Override
    public void executeAddRule(QueryParam param) {
        LOGGER.info("Parameter data:"+param.getParamId()+";"+param.getParamSign());
        ParamInfo paramInfo = new ParamInfo() ;
        paramInfo.setId(param.getParamId());
        paramInfo.setParamSign(param.getParamSign());
        paramInfo.setCreateTime(new Date());
        paramInfo.setUpdateTime(new Date());
        ParamInfoService paramInfoService = (ParamInfoService)SpringContextUtil.getBean("paramInfoService") ;
        paramInfoService.insertParam(paramInfo);
    }
    @Override
    public void executeRemoveRule(QueryParam param) {
        LOGGER.info("Parameter data:"+param.getParamId()+";"+param.getParamSign());
        ParamInfoService paramInfoService = (ParamInfoService)SpringContextUtil.getBean("paramInfoService") ;
        ParamInfo paramInfo = paramInfoService.selectById(param.getParamId());
        if (paramInfo != null){
            paramInfoService.removeById(param.getParamId()) ;
        }
    }
}

3. Rule Call Interface

@RestController
@RequestMapping("/rule")
public class RuleController {
    @Resource
    private KieSession kieSession;
    @Resource
    private RuleEngineService ruleEngineService ;
    @RequestMapping("/param")
    public void param (){
        QueryParam queryParam1 = new QueryParam() ;
        queryParam1.setParamId("1");
        queryParam1.setParamSign("+");
        QueryParam queryParam2 = new QueryParam() ;
        queryParam2.setParamId("2");
        queryParam2.setParamSign("-");
        // Participation
        kieSession.insert(queryParam1) ;
        kieSession.insert(queryParam2) ;
        kieSession.insert(this.ruleEngineService) ;
        // Return parameter
        RuleResult resultParam = new RuleResult() ;
        kieSession.insert(resultParam) ;
        kieSession.fireAllRules() ;
    }
}

In this way, the complete case is over.

4. Source code address

GitHub·address
https://github.com/cicadasmile/middle-ware-parent
GitEE·address
https://gitee.com/cicadasmile/middle-ware-parent