Drools executes the specified rule

1、 background

Before we write drools In the process of rule file , May write a lot of rules .drools When the engine matches patterns , It may activate many rules at once , But I just want to enforce a specified rule , So how to operate at this time ？

2、 programme

2.1 adopt AgendaFilter To achieve

We know , stay drools When pattern matching , Will match all the rules , The rules that match successfully will be put into Agenda( agenda ) in , and fireAllRules(AgendaFilter) Method , You can pass a AgendaFilter Yes Agenda Filter the activated rules in .

2.2 adopt entry-point To achieve

Use entry-point You can define the entry point or event flow corresponding to the data source of the schema . _{This cannot be fully realized , It's just a way of thinking .}

for instance ：

Api(api == "/users/info" ) from entry-point "first-entry-point"

Api api = new Api("/users/info", 100);
EntryPoint entryPoint = kieSession.getEntryPoint("second-entry-point");
entryPoint.insert(api);
kieSession.fireAllRules();

The above example , Although there are... In working memory Api This object , But because of In the rules entry-point and java In code entry-point atypism , Rules are not matched successfully .

3、 Realization

Here we pass AgendaFilter To call a specific rule .

3.1 demand

We have a Api(api,invokedCnt) object

Rule one ： There is... In the working memory Api object , And attribute api=="/users/info".
Rule 2 ： There is... In the working memory Api object , And attribute invokedCnt > 10.

We insert a... Into the working memory Api("/users/info",100), At this point, both rule 1 and rule 2 will match , But I just want to enforce rule two .

3.2 drl Documentation

package rules

import com.huan.drools.Api

rule "rule_agenda_filter_01"
    when
        $api: Api(api == "/users/info" )
    then
        System.out.println(" The current rule is : " + drools.getRule().getName());
end

rule "rule_agenda_filter_02"
    when
        $api: Api(invokedCnt > 10)
    then
        System.out.println(" The current rule is : " + drools.getRule().getName());
end

3.3 part java Code

Api api = new Api("/users/info", 100);
kieSession.insert(api);

//  After all the patterns are matched successfully, the rules will go back to agenda in , And then through AgendaFilter Filter out the rules to be executed 
kieSession.fireAllRules(new AgendaFilter() {
    
    @Override
    public boolean accept(Match match) {
    
        String ruleName = match.getRule().getName();
        return Objects.equals(ruleName, "rule_agenda_filter_02");
    }
});

You can see here through AgendaFilter Filter the rules , Only execute rule_agenda_filter_02 The rules .

Be careful ： Although this is a filter , But that doesn't mean only rule_agenda_filter_02 The rule is active , But all the rules that meet the conditions are activated .

3.4 Running results

 The current rule is : rule_agenda_filter_02

We can see that we have achieved the results we want .

4、 Complete code

https://gitee.com/huan1993/spring-cloud-parent/tree/master/drools/drools-invoked-specify-rule