Drools (5): drools basic syntax (3)

The rule syntax of the attribute part

Drools The attributes provided in are shown in the following table ：

Property name	explain
salience	Specify rule execution ⾏ priority
dialect	Specify rules to make ⽤ The language of ⾔ type , The value is java and mve
enabled	Specify whether the rule is enabled ⽤
date-effective	Specify the rules ⽣ Effective time
date-expires	Specify the rule expiration time
activation-group	Activate grouping , Rules with the same group name can only have ⼀ Rules trigger
agenda-group	Agenda groups , Only the rules in the focus group can trigger
timer	Timer , Specify when the rule is triggered
auto-focus	⾃ Move to get focus ,⼀ Like a combination agenda-group⼀ Start to make ⽤
no-loop	prevent ⽌ Dead cycle

1 salience

The function is to set rule execution ⾏ The priority of the ,salience The value of the property is ⼀ A digital , The more numbers ⼤ Of board ⾏ The higher the priority ⾼. Default love Condition , Regular salience The default value is 0. If not set salience attribute , Enforcement of rule body ⾏ The order is from top to bottom .

Example ：

rule "attributes_rule1" 
    salience 1 
    when
        eval(true) 
    then
        System.out.println("rule1...."); 
end 

rule "attributes_rule2" 
    salience 2 
    when
        eval(true) 
    then
        System.out.println("rule2...."); 
end

test ：

    @Test
    public void test7() {
        KieServices kieServices = KieServices.Factory.get();
        KieContainer kieContainer = kieServices.getKieClasspathContainer();
        // Conversation object ,⽤ Interact with the rule engine 
        KieSession kieSession = kieContainer.newKieSession();
        // Activate rule engine , If the match is successful, execute ⾏ The rules 
        kieSession.fireAllRules();
        //  Close session 
        kieSession.dispose();
    }

  Execution results ：

2 no-loop

The function is to control the execution ⾏ The rules of the past are full again ⾜ Whether to execute again ⾏.no-loop The value of the property is ⼀ A Boolean , By default, the rules are no-loop The value of the property is false, If no-loop The property value is true, Then it means that the rule will only be Engine check ⼀ Time , If full ⾜ Conditions are enforced ⾏ Regular RHS part , If the engine inside because of Fact The update causes the engine to start the check rule again , that It will ignore all no-loop Property is set to true The rules of .

Example ：

// test no-loop
rule "attributes_rule3"
    salience 1
    no-loop true
    when
        $customer:Customer(name==" Zhang San ")
    then
        update($customer);
        System.out.println("customer name:"+$customer.getName());
end

test ：

    @Test
    public void test8() {
        KieServices kieServices = KieServices.Factory.get();
        KieContainer kieContainer = kieServices.getKieClasspathContainer();
        // Conversation object ,⽤ Interact with the rule engine 
        KieSession kieSession = kieContainer.newKieSession();
        Customer customer = new Customer();
        customer.setName(" Zhang San ");
        kieSession.insert(customer);
        // Activate rule engine , If the match is successful, execute ⾏ The rules 
        kieSession.fireAllRules();
        // Activate rule engine , If the match is successful, execute ⾏ The rules 
        kieSession.fireAllRules();
        //  Close session 
        kieSession.dispose();
    }

test result ：

Add the no-loop Set to false

You will find that you have been executing an endless loop

Add the no-loop Set to true

The rule only executes once and ends

3 date-effective

do ⽤ yes ⽤ To control that the rule will only be triggered after arrival , In the rule of transportation ⾏ when , The engine will be ⾃ When taking the current operating system, it is the same as date-effective Set the time value into ⾏⽐ Yes , Only when the system time >=date-effective Set the time value of , Rules will trigger execution ⾏, Otherwise, hold on to ⾏ Will not hold ⾏. Without setting this property , Rules can be triggered at any time , There is no such limitation .

date-effective The value of is ⼀ individual ⽇ Period type string , By default ,date-effective Acceptable ⽇ The format of the period is “dd- MMM-yyyy” In the process of actual use , If you don't want to ⽤ This time format , Then you can adjust ⽤ Of Java Code by making ⽤ System.setProperty(String key,String value)⽅ Method to modify the default time format stay java⽂ Add this command to the file : System.setProperty("drools.dateformat","yyyy-MM-dd");

Example :

rule "attributes_rule4"
    date-effective "2022-7-20"
    // At present ⽇ Period not ⼩ On 2022-7-20 You can hold ⾏
    when
        eval(true);
    then
        System.out.println("attributes_rule4 is execution!");
end

test ：

    @Test
    public void test8() {
        // Set and modify the default time format 
        System.setProperty("drools.dateformat", "yyyy-MM-dd");
        KieServices kieServices = KieServices.Factory.get();
        KieContainer kieContainer = kieServices.getKieClasspathContainer();
        // Conversation object ,⽤ Interact with the rule engine 
        KieSession kieSession = kieContainer.newKieSession();
        // Activate rule engine , If the match is successful, execute ⾏ The rules 
        kieSession.fireAllRules();
        //  Close session 
        kieSession.dispose();
    }

test result ： 

Test date is 2022 year 7 month 26 Japan , Greater than the set 2022 year 7 month 20 Japan

4 date-expires

do ⽤ Is with the date-effective Attributes are just the opposite ,date-expires Works of ⽤ yes ⽤ To set the validity period of the rule , The engine is running ⾏ When the rules are , Will check if the rules have date-expires attribute , If any , Then the value of this attribute will be compared with the current system Time goes in ⾏⽐ Yes , If ⼤ At system time , Then the rules will be enforced ⾏, Otherwise, don't cling ⾏.

5 enabled

do ⽤ yes ⽤ To define ⼀ Whether a rule can ⽤ Of . The value of this property is ⼀ A Boolean value , The default value of this attribute is true, Indicates that the rule is ⽤ Of . Set up enabled The property value is false, Then the engine will not execute ⾏ This rule

6 dialect

do ⽤ yes ⽤ To define the rules that make ⽤ The language of ⾔ type ,⽬ front ⽀ Hold two types of language ⾔：mvel and java, By default , without ⼿⼯ Set the of rules dialect, Then make ⽤ Of java language ⾔

7 activation-group

do ⽤ Is will if ⼲ The rules are divided into ⼀ A set of ,⽤⼀ String to name this group , In this way, I am clinging to ⾏ When , Have the same activation-group As long as there is ⼀ One will be held ⾏, Other rules will no longer be enforced ⾏.

in other words , stay ⼀ Groups have the same activation-group In the rules of attributes , Only ⼀ Rules will be enforced ⾏, Other rules will not be enforced ⾏. Of course, for people with the same activation-group Which of the rules of attributes ⼀ One meeting first ⾏, Then you can ⽤ similar salience And so on .

Example ：

// test activation-group
rule "attributes_rule5"
activation-group "test"
    when
        eval(true)
    then
        System.out.println("attributes_rule5 execute...");
end
rule "attributes_rule6"
    activation-group "test"
    when
        eval(true)
    then
        System.out.println("attributes_rule6 execute...");
end

test ：

    @Test
    public void test9() {
        // Set and modify the default time format 
        KieServices kieServices = KieServices.Factory.get();
        KieContainer kieContainer = kieServices.getKieClasspathContainer();
        // Conversation object ,⽤ Interact with the rule engine 
        KieSession kieSession = kieContainer.newKieSession();
        // Activate rule engine , If the match is successful, execute ⾏ The rules 
        kieSession.fireAllRules();
        //  Close session 
        kieSession.dispose();
    }

test result ：

8 agenda-group

do ⽤ yes agenda-group The value of the property is also ⼀ A string , Through this string , Rules can be divided into if ⼲ individual Agenda Group, By default , The engine is in tune ⽤ These settings agenda-group Attribute rules need to be displayed to specify a Agenda Group obtain Focus（ The focus of ）, This is where Agenda Group The rules in it will trigger execution ⾏, Otherwise, it will not be executed .

Example ：

// test agenda-group
rule "attributes_rule7"
    agenda-group "001"
    when
        eval(true)
    then
        System.out.println("attributes_rule7 execute");
end

rule "attributes_rule8"
    agenda-group "002"
    when
        eval(true)
    then
        System.out.println("attributes_rule8 execute...");
end

test ：

    @Test
    public void test10() {
        // Set and modify the default time format 
        KieServices kieServices = KieServices.Factory.get();
        KieContainer kieContainer = kieServices.getKieClasspathContainer();
        // Conversation object ,⽤ Interact with the rule engine 
        KieSession kieSession = kieContainer.newKieSession();
        kieSession.getAgenda().getAgendaGroup("002").setFocus();
        // Get hold ⾏  The focus of 
        //  Activate rule engine , If the match is successful, execute ⾏ The rules 
        kieSession.fireAllRules();
        //  Close session 
        kieSession.dispose();
    }

test result ： 

9 auto-focus

do ⽤ yes ⽤ Come on, it has been set agenda-group Set whether the rule can ⾃ Move alone Focus, If this property is set to true, Then in the engine execution ⾏ when , You don't need to display something Agenda Group Set up Focus, Otherwise, we need .

Example ：

rule "attributes_rule7"
    agenda-group "001"
    auto-focus
    when
        eval(true)
    then
        System.out.println("attributes_rule7 execute");
end

rule "attributes_rule8"
    agenda-group "002"
    when
        eval(true)
    then
        System.out.println("attributes_rule8 execute...");
end

test ：

    @Test
    public void test12() {
        // Set and modify the default time format 
        KieServices kieServices = KieServices.Factory.get();
        KieContainer kieContainer = kieServices.getKieClasspathContainer();
        // Conversation object ,⽤ Interact with the rule engine 
        KieSession kieSession = kieContainer.newKieSession();
        // Get hold ⾏  The focus of 
        //  Activate rule engine , If the match is successful, execute ⾏ The rules 
        kieSession.fireAllRules();
        //  Close session 
        kieSession.dispose();
    }

test result ：

 

10 timer

timer Attributes can be set through the ⽅ Specify rule execution ⾏ Time for , send ⽤⽅ There are two kinds of ：

⽅ type ⼀：timer (int: ?)

This kind of ⽅ Follow java.util.Timer The cause of the object ⽤⽅ type , The first ⼀ The parameters represent ⼏ Seconds later ⾏, The first ⼆ Parameters represent every ⼏ Second hold ⾏⼀ Time , The first ⼆ Parameters are optional .

⽅ type ⼆：timer(cron: )

This kind of ⽅ Shi Shi ⽤ The standard unix cron The use of expressions ⽤⽅ Formula to define the time of rule execution .

Example ：