drools中的无状态与有状态会话行为

Question

我对口水还不熟悉。我试图理解Drools提供的无状态会话和有状态会话之间的区别。

根据我的初步理解，

在无状态会话的情况下，如果在任何规则的操作执行过程中修改了事实，则不会将其重新提交给推理引擎以找出与修改后的事实匹配的新规则。

在状态会话的情况下，如果在任何规则的操作执行过程中修改了事实，则它将被重新提交给推理引擎以找出与修改后的事实相匹配的新规则，然后执行相应的操作。

因此，当我试图通过编写一个示例规则来验证这种行为时，我发现这两种情况下的行为完全相同。所以现在我对有状态会话和无状态会话之间的区别感到困惑。

我想请大家帮助我理解有状态和无状态会话的正确行为。

我正在粘贴有状态和无状态会话的示例代码及其输出和示例规则，以供参考。

licenseApplication.drl   (Rule file)

package com.idal.droolsapp

rule "Is of valid age"
    no-loop
when
    $a : Applicant( age < 18 )
then
    System.out.println( "Not eligible for license" );
    System.out.println( "Setting Valid to false" );
    modify( $a ) { setValid( false ) };
end

rule "Is of valid false"
    salience 100
when
    $a : Applicant( valid == false )
then
    System.out.println( "Second rule fired" );
end

输入对象（事实）申请人。Java语言

package com.idal.droolsapp;

public class Applicant {

    private String name;

    private int age;

    private boolean valid = true;

    public Applicant(String name, int age) {
        setName(name);
        setAge(age);
    }

    public void setName(String name) {
        this.name = name;
    }

    public String getName() {
        return name;
    }

    public void setAge(int age) {
        this.age = age;
    }

    public int getAge() {
        return age;
    }

    public void setValid(boolean valid) {
        this.valid = valid;
    }

    public boolean isValid() {
        return valid;
    }

    @Override
    public String toString() {
        return "Applicant [name=" + name + ", age=" + age + ", valid=" + valid
                + "]";
    }


}

无状态会话示例。java（无状态会话测试代码）

package com.idal.droolsapp;

import org.drools.KnowledgeBase;
import org.drools.KnowledgeBaseFactory;
import org.drools.builder.KnowledgeBuilder;
import org.drools.builder.KnowledgeBuilderFactory;
import org.drools.builder.ResourceType;
import org.drools.io.ResourceFactory;
import org.drools.runtime.StatelessKnowledgeSession;

public class StatelessSessionExample {

    /**
     * @param args
     */
    public static void main(String[] args) {

        KnowledgeBuilder kbuilder = KnowledgeBuilderFactory
                .newKnowledgeBuilder();

        kbuilder.add(ResourceFactory.newClassPathResource(
                "licenseApplication.drl", StatelessSessionExample.class),

        ResourceType.DRL);

        if (kbuilder.hasErrors()) {

            System.err.println(kbuilder.getErrors().toString());

        }

        KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();

        kbase.addKnowledgePackages(kbuilder.getKnowledgePackages());

        StatelessKnowledgeSession ksession = kbase.newStatelessKnowledgeSession();

        Applicant applicant = new Applicant( "Mr John Smith", 16 );

        ksession.execute( applicant );

        System.out.println("Updated Applicant = " + applicant);
    }

}

无状态会话测试代码输出：

Not eligible for license
Setting Valid to false
Second rule fired
Updated Applicant = Applicant [name=Mr John Smith, age=16, valid=false]

StatefulSessionExample。java（无状态会话测试代码）

package com.idal.droolsapp;

import org.drools.KnowledgeBase;
import org.drools.KnowledgeBaseFactory;
import org.drools.builder.KnowledgeBuilder;
import org.drools.builder.KnowledgeBuilderFactory;
import org.drools.builder.ResourceType;
import org.drools.io.ResourceFactory;
import org.drools.runtime.StatefulKnowledgeSession;

public class StatefulSessionExample {

    /**
     * @param args
     */
    public static void main(String[] args) {

        KnowledgeBuilder kbuilder = KnowledgeBuilderFactory
                .newKnowledgeBuilder();

        kbuilder.add(ResourceFactory.newClassPathResource(
                "licenseApplication.drl", StatefulSessionExample.class),

        ResourceType.DRL);

        if (kbuilder.hasErrors()) {

            System.err.println(kbuilder.getErrors().toString());

        }

        KnowledgeBase kbase = KnowledgeBaseFactory.newKnowledgeBase();

        kbase.addKnowledgePackages(kbuilder.getKnowledgePackages());

        StatefulKnowledgeSession ksession = kbase.newStatefulKnowledgeSession();

        Applicant applicant = new Applicant( "Mr John Smith", 16 );

        ksession.insert( applicant );

        ksession.fireAllRules();

        ksession.dispose();

        System.out.println("Updated Applicant = " + applicant);
    }

}

状态会话测试代码输出：

Not eligible for license
Setting Valid to false
Second rule fired
Updated Applicant = Applicant [name=Mr John Smith, age=16, valid=false]

再次请大家帮助我理解有状态和无状态会话的正确行为。

提前谢谢你，曼尼什·甘地

Answer 1

据我所知，当您在无状态会话中触发规则时，更改不会触发新规则。但这并不意味着规则不会因为更改而被触发。第一条规则更改了有效的值，这意味着当您检查第二条规则的条件有效时，它已经为假，并且规则会触发。

如果更改影响了前一条规则的“何时”部分，则在无状态会话中，第一条规则不会再次触发，而在第一条规则中会再次触发。