Drools basic grammar

One 、 introduce Jar package , To configure POM file

Jump 1

Two 、 More detailed syntax

Jump 2

3、 ... and 、 Introduction to expression syntax

The simplest rule to complete , Grammar should also include these

rule "name"
	when
		......
	then
		......
end

Case study 1

rule "withdraw 11"
    agenda-group "trade.withdraw"
    enabled true
    salience 11
    when
        $routeResult: RouteResult()
        $request: WithdrawRouteRuleRequest()
        $payer: RouteRuleRequestAccount(accountType == "AAA" && fundPlSettleModel == "BBB") from $ request.getPayer()
    then
        logger.info("{} Match to rule , Return scenario code {}",$request.getIdempotenceNo(),"trade.withdraw.1001");
        $routeResult.setResult(true);
        $routeResult.setBusinessScenariosCode("trade.withdraw.1001");
end

rule “withdraw 11” rule Indicates that this is a rule , Rule name withdraw 11

1、salience

Used to set the priority of rule execution ,salience The value of the property is a number , The higher the number, the higher the execution priority , And its value can be a negative number . By default , Regular ssalience The default value is 0, So if we don't set the rules manually salience attribute , Then its execution order is random （ But it is generally in the loading order .）

2、enabled

enabled Properties are relatively simple , It is used to define whether a rule is available . The value of this attribute is a Boolean value , The default value of this attribute is true, Indicates that the rule is available , If you add a rule manually enabled attribute , And set it enabled The property value is false, Then the engine will not execute the rule

3、agenda-group

The engine is invoking these settings agenda-group Attribute rules need to be displayed to specify a Agenda Group obtain Focus（ The focus of ）, For example, the following code

//getSession  obtain KieSession  I wrote it myself .
KieSession ks = getSession();
// Set up agenda-group  Of auto-focus Make it execute  
ks.getAgenda().getAgendaGroup("group1").setFocus();

notes ： Filter the rule name , Only execute the rules under a rule name

kSession.fireAllRules(new RuleNameEqualsAgendaFilter("man"))    
//【man】 It's the name of the rule , That is to say rule "man"

Case study 2

rule "withdraw 11"
    agenda-group "trade.withdraw"
    enabled true
    salience 11
    when
        $routeResult: RouteResult()  // Judge that there must be RouteResult Type object 
        $request: WithdrawRouteRuleRequest() // Judge that there must be WithdrawRouteRuleRequest type 
		
		//$request.getPayer()  Represents the variable defined above $request Object has a variable payer
        //payer The object must be RouteRuleRequestAccount type ,payer Properties in objects accountType
        $payer: RouteRuleRequestAccount(accountType == "A" && fundPlSettleModel == "B") 
        from $request.getPayer()
    then
        logger.info("{} Match to rule , Return scenario code {}",$request.getIdempotenceNo(),"trade.withdraw.1001");
        $routeResult.setResult(true);
        $routeResult.setBusinessScenariosCode("trade.withdraw.1001");
end

1、from

from The role of ： Specify the left side as its source , As the variable to be used in the expression on the right . Here is an example ,from Usage of .

RouteRuleRequest routeRuleRequest = new RouteRuleRequest ();
kieSession.insert(routeRuleRequest ); 
// Go to kieSession There is a routeRuleRequest  Object of type , Or set the object to the working memory .

## Judge whether it includes TransferRouteRuleRequest Object of type , If there is an assignment to $request This variable .
$request: RouteRuleRequest ()   

$receiver: RouteRuleRequestAccount(accountType == 1) from $request.getReceiver()

The above code means , from $request Take one of them 【 Attribute variables receiver】, Then assign a value to the left expression , That is, assign values to the following code

$receiver: RouteRuleRequestAccount(accountType == 1)

On the left, judge this variable receiver Whether it is RouteRuleRequestAccount type , And the attributes inside accountType Is it equal to 1, Then give this result to $receiver This variable .

Case study 3

$request: TransferRouteRuleRequest()
$modeType: TransferRouteRuleRequest(modeType == 2)
$platform: TransferRouteRuleRequest(isSamePlatform == 1)

TransferRouteRuleRequest Bracket judgment data , Can write many lines , The default is and Splicing

Four 、 operation List

kieSession.insert(list); // Set the set to the working memory 

## Rule handling ： Print out all List The elements in the collection 
rule "hello_0"
    when
        $li:List(size > 0)  ## Get all in working memory in turn List Assemble to $li
        $m:Animal(name == "cat") from $li   ## obtain List in name = "cat"  Of Animal object , There may be more than one , There may be only one .
    then
        ## Print the current List Medium message
        ## Be careful , It will be executed many times , The number of executions is all List Total number of collection elements （ Note that it is not current List The total number of collections ）
        ## Because the rules filter out a completely consistent one from the working memory conditions The data of , Will be in agenda Insert a combination of rule and matching data , Again by agenda Responsible for enforcing the rules .
        System.out.println("id:"+$m.getId()+",name:"+$m.getName());
end