Drools

https://docs.drools.org/latest/drools-docs/drools/
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Drools is an open source rule engine and decision management system that provides forward-chaining...
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### Example FindApprovedLoansEndpoint REST Endpoint Setup

Source: https://docs.drools.org/latest/drools-docs/drools/migration-guide/index.html

Setup for a REST endpoint that exposes rule evaluation. It uses a static KieContainer for efficient rule loading.

```java
@Path("/find-approved")
public class FindApprovedLoansEndpoint {

   private static final KieContainer kContainer = KieServices.Factory.get().newKieClasspathContainer();

   @POST()
   @Produces(MediaType.APPLICATION_JSON)
   @Consumes(MediaType.APPLICATION_JSON)
   public List<LoanApplication> executeQuery(LoanAppDto loanAppDto) {
   	KieSession session = kContainer.newKieSession();

   	List<LoanApplication> approvedApplications = new ArrayList<>();
   	session.setGlobal("approvedApplications", approvedApplications);
   	session.setGlobal("maxAmount", loanAppDto.getMaxAmount());

   	loanAppDto.getLoanApplications().forEach(session::insert);
   	session.fireAllRules();
   	session.dispose();

   	return approvedApplications;
   }
}
```

--------------------------------

### Build and Install Maven Project

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Standard Maven command to build and install the project. This is a prerequisite for deploying Drools resources to the classpath.

```bash
mvn install
```

--------------------------------

### BatchExecution Command Example

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Executes a batch of commands, including inserting objects, starting a process, and executing a query. Results from commands with out identifiers are added to the ExecutionResults.

```java
StatelessKieSession ksession = kbase.newStatelessKieSession();

List cmds = new ArrayList();
cmds.add( CommandFactory.newInsertObject( new Cheese( "stilton", 1), "stilton") );
cmds.add( CommandFactory.newStartProcess( "process cheeses" ) );
cmds.add( CommandFactory.newQuery( "cheeses" ) );
ExecutionResults bresults = ksession.execute( CommandFactory.newBatchExecution( cmds ) );
Cheese stilton = ( Cheese ) bresults.getValue( "stilton" );
QueryResults qresults = ( QueryResults ) bresults.getValue( "cheeses" );
```

--------------------------------

### Example Usage of Keywords for Imports, Headers, etc.

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

A comprehensive example showcasing the usage of various column headers, including keywords for imports and attributes that are not applied.

```drools
CONDITION
---
Person
age == $param
Persons age
42
```

```drools
CONDITION
---
Person
age < 
Persons age
42
```

```drools
c : Cheese
type
Cheese type
stilton
```

```drools
list.add("$param");
Log
Old man stilton
```

--------------------------------

### Build and Install KieModule (Maven)

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Use this Maven command to build and install a programmatically generated KieModule. This is part of the default build process.

```bash
mvn install
Copied!
```

--------------------------------

### Example Maven Build Output

Source: https://docs.drools.org/latest/drools-docs/drools/getting-started/index.html

This is an example of the console output after running 'mvn clean verify', showing the test execution status for the TrafficViolationTest.

```text
[INFO] -------------------------------------------------------
[INFO]  T E S T S
[INFO] -------------------------------------------------------
[INFO] Running org.example.TrafficViolationTest
2022-08-29 16:11:44,539 [main] INFO  Evaluating DMN model
2022-08-29 16:11:44,540 [main] INFO  Checking results: DMNResultImpl{context={
    Driver: {
        Points: 2
    }
    Violation: {
        Type: speed
        Speed Limit: 100
        Actual Speed: 120
    }
    Fine: {
        Points: 3
        Amount: 500
    }
    Should the driver be suspended?: No
}
, messages=org.kie.dmn.core.util.DefaultDMNMessagesManager@4f89331f}
[INFO] Tests run: 1, Failures: 0, Errors: 0, Skipped: 0, Time elapsed: 0.001 s - in org.example.TrafficViolationTest
```

--------------------------------

### Example JVM Execution Command

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Illustrates how to execute an application with KIE security policies enabled using JVM parameters.

```bash
java -Djava.security.manager -Djava.security.policy=global.policy -Dkie.security.policy=rules.policy         foo.bar.MyApp
```

--------------------------------

### Console Output Example

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Illustrates the output from a stateful KIE session, showing actions taken and the final state.

```text
> Cancel the alarm
> Turn off the sprinkler for room office
> Turn off the sprinkler for room kitchen
> Everything is ok
```

--------------------------------

### Accumulate CE example for order discounts

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Demonstrates using the 'accumulate' CE to calculate the total value of order items for applying discounts. This example uses Java as the semantic dialect and shows how to initialize, accumulate, and retrieve a result.

```drl
rule "Apply 10% discount to orders over US$ 100,00"
when
    $order : Order()
    $total : Number( doubleValue > 100 )
             from accumulate( OrderItem( order == $order, $value : value ),
                              init( double total = 0; ),
                              action( total += $value; ),
                              reverse( total -= $value; ),
                              result( total ) )
then
    // apply discount to $order
end
Copied!
```

--------------------------------

### Accumulate CE example with custom objects

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Shows how to use the 'accumulate' CE to instantiate and populate custom objects. This example demonstrates accumulating data from 'Cheese' objects into a 'Cheesery' object.

```drl
rule "Accumulate using custom objects"
when
    $person   : Person( $likes : likes )
    $cheesery : Cheesery( totalAmount > 100 )
                from accumulate( $cheese : Cheese( type == $likes ),

```

--------------------------------

### Register and Start KieScanner with Maven Repository

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

This snippet shows how to register and start a KieScanner to poll a Maven repository at a specified interval. It requires kie-ci.jar on the classpath.

```java
KieServices kieServices = KieServices.Factory.get();
ReleaseId releaseId = kieServices.newReleaseId( "org.acme", "myartifact", "1.0-SNAPSHOT" );
KieContainer kContainer = kieServices.newKieContainer( releaseId );
KieScanner kScanner = kieServices.newKieScanner( kContainer );

// Start the KieScanner polling the Maven repository every 10 seconds
kScanner.start( 10000L );
```

--------------------------------

### Register and Start KIE Scanner

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Register and start a KIE scanner for a KIE container, configuring it to poll the Maven repository at a specified interval. Ensure the 'kie-ci.jar' is on the classpath. The project version must be a SNAPSHOT version.

```java
import org.kie.api.KieServices;
import org.kie.api.builder.ReleaseId;
import org.kie.api.runtime.KieContainer;
import org.kie.api.builder.KieScanner;

...

KieServices kieServices = KieServices.Factory.get();
ReleaseId releaseId = kieServices
  .newReleaseId("com.sample", "my-app", "1.0-SNAPSHOT");
KieContainer kContainer = kieServices.newKieContainer(releaseId);
KieScanner kScanner = kieServices.newKieScanner(kContainer);

// Start KIE scanner for polling the Maven repository every 10 seconds (10000 ms)
kScanner.start(10000L);

```

--------------------------------

### Start KieScanner On-Demand

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Demonstrates how to use the scanNow() method to trigger a KieScanner update on demand, instead of using a fixed time interval.

```java
kScanner.scanNow();
```

--------------------------------

### Example JSON Response for Approved Loans

Source: https://docs.drools.org/latest/drools-docs/drools/migration-guide/index.html

Example JSON response showing the list of loan applications that were approved based on the rule evaluation.

```json
[
  {
    "id": "ABC10001",
    "applicant": {
      "name": "John",
      "age": 45
    },
    "amount": 2000,
    "deposit": 1000,
    "approved": true
  }
]
```

--------------------------------

### Flat Text Output Example

Source: https://docs.drools.org/latest/drools-docs/drools/experimental-features/index.html

Example of flat text output from TextReporter, listing changed and impacted rules.

```text
--- toFlatText ---
Inventory shortage[+]
PriceCheck_11[*]
StatusCheck_11[+]
StatusCheck_12[+]
StatusCheck_13[+]
```

--------------------------------

### Query Response Example

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

This is an example of the JSON response received after invoking the '/high-severity' query endpoint. It shows the 'alerts' array containing objects that match the query criteria.

```json
{
    "alerts" : [
        {
            "severity" : "HIGH",
            "message" : "Temperature exceeds threshold: 100"
        }
    ]
}
```

--------------------------------

### String Literal Example

Source: https://docs.drools.org/latest/drools-docs/drools/DMN/index.html

Demonstrates a basic string literal in FEEL.

```FEEL
"John Doe"
```

--------------------------------

### DSL Expansion Examples

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Demonstrates how the defined DSL rules are expanded into standard DRL syntax. Shows expansion of single and chained conditions.

```drl
Person(name="Kitty")
```

```drl
Person(age >= 42, location="Atlanta")
```

```drl
System.out.println("boo");
```

```drl
Person(name="Bob") and Person(age >= 30, location="Utah")
```

--------------------------------

### Keyword Definition Example

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Defines a keyword replacement, changing 'regula' to 'rule'.

```dsl
[keyword][]regula=rule
```

--------------------------------

### Example Interval Timer Attributes

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Illustrates the syntax for interval timers in DRL, specifying initial delay and repeat intervals.

```drl
// Run after a 30-second delay
timer ( int: 30s )

// Run every 5 minutes after a 30-second delay each time
timer ( int: 30s 5m )
```

--------------------------------

### Maven Settings.xml Profile Activation

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Example of activating a Maven profile by default in settings.xml. This is used for configuring remote repositories.

```xml
<profiles>
  <profile>
    <id>profile-1</id>
    <activation>
      <activeByDefault>true</activeByDefault>
    </activation>
    ...
  </profile>
</profiles>
```

--------------------------------

### Build KieFileSystem Contents and Create KieContainer

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

This example shows the complete process of building the contents of a KieFileSystem, which automatically adds the resulting KieModule to the KieRepository. It then demonstrates creating a KieContainer using the KieModule's ReleaseId.

```java
KieServices kieServices = KieServices.Factory.get();

```

--------------------------------

### Get Global Command Example

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Executes a GetGlobal command to retrieve an existing global variable from the session. An optional String argument can specify an alternative return name.

```java
StatelessKieSession ksession = kbase.newStatelessKieSession();
ExecutionResults bresults =
    ksession.execute( CommandFactory.getGlobal( "stilton" );
Cheese stilton = bresults.getValue( "stilton" );
```

--------------------------------

### Accessing List Elements by Positive Index

Source: https://docs.drools.org/latest/drools-docs/drools/DMN/index.html

Elements in a FEEL list can be accessed by index, starting from 1 for the first element. This example retrieves the second element of list 'x'.

```feel
x[2]
```

--------------------------------

### EventA started by EventB

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

This pattern matches if EventA and EventB start at the same time, and EventB ends before EventA ends. This is the reverse behavior of the 'starts' operator.

```java
$eventA : EventA(this startedby $eventB)
```

```java
$eventA.startTimestamp == $eventB.startTimestamp
&&
$eventA.endTimestamp > $eventB.endTimestamp
```

--------------------------------

### Rule with 'from entry-point'

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Demonstrates using 'from entry-point' to specify a data source for a pattern, often used with event streams.

```java
rule "Authorize withdrawal"
  when
    WithdrawRequest( $ai : accountId, $am : amount ) from entry-point "ATM Stream"
    CheckingAccount( accountId == $ai, balance > $am )
  then
    // Authorize withdrawal.
end
```

--------------------------------

### Conditions for EventA starts EventB

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Specifies the conditions for EventA starting before or at the same time as EventB, and ending before EventB ends: EventA's start timestamp must equal EventB's start timestamp, and EventA's end timestamp must be less than EventB's end timestamp.

```drl
$eventA.startTimestamp == $eventB.startTimestamp
&&
$eventA.endTimestamp < $eventB.endTimestamp
```

--------------------------------

### Legacy DRL Rule Condition Elements Example

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Illustrates the use of init, action, reverse, and result in a legacy DRL rule condition.

```java
init( Cheesery cheesery = new Cheesery(); ),
action( cheesery.addCheese( $cheese ); ),
reverse( cheesery.removeCheese( $cheese ); ),
result( cheesery ) );
then
    // do something
end
```

--------------------------------

### DRL Constraint Example

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

An example of a standard DRL rule condition with multiple field constraints.

```drl
Cheese(age < 5, price == 20, type=="stilton", country=="ch")
```

--------------------------------

### EventA started by EventB within 5 seconds

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

This pattern matches if EventA starts within 5 seconds of EventB, and EventB ends before EventA ends. It requires that the absolute difference between their start timestamps is less than or equal to 5 seconds.

```java
$eventA : EventA( this starts[5s] $eventB)
```

```java
abs( $eventA.startTimestamp - $eventB.startTimestamp ) <= 5s
&&
$eventA.endTimestamp > $eventB.endTimestamp
```

--------------------------------

### Example of Functions for Computing Price and Discount

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Demonstrates the use of Import, Functions, and RuleSet keywords in a decision table to define helper functions for rule execution.

```java
function int computePrice(Cheese cheese) {
    if (cheese.getType() == "cheddar") {
        return 10;
    } else if (cheese.getType() == "stilton") {
        return 15;
    } else {
        return 20;
    }
}

function boolean hasDiscount(Person person) {
    if (person.getAge() > 60) {
        return true;
    } else {
        return false;
    }
}
```

--------------------------------

### EventA starts EventB within 5 seconds

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

This pattern matches if EventA starts within 5 seconds of EventB. It requires that the absolute difference between their start timestamps is less than or equal to 5 seconds, and EventA ends before EventB ends.

```java
$eventA : EventA(this starts[5s] $eventB)
```

```java
abs($eventA.startTimestamp - $eventB.startTimestamp) <= 5s
&&
$eventA.endTimestamp < $eventB.endTimestamp
```

--------------------------------

### Date and Time Construction Examples

Source: https://docs.drools.org/latest/drools-docs/drools/DMN/index.html

Demonstrates constructing date and time values using the `date and time()` function. Supports formats including timezone offsets and UTC.

```FEEL
date and time( "2017-10-22T23:59:00" )
```

```FEEL
date and time( "2017-06-13T14:10:00+02:00" )
```

```FEEL
date and time( "2017-02-05T22:35:40.345-05:00" )
```

```FEEL
date and time( "2017-06-13T15:00:30z" )
```

--------------------------------

### Example Cron Timer Attribute

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Shows an example of a cron timer attribute in DRL for scheduling rule execution.

```drl
// Run every 15 minutes
timer ( cron:* 0/15 * * * ? )
```

--------------------------------

### Instance Creation Using Key Constructor

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

This example illustrates how to instantiate a fact type using a constructor generated based on the key attributes. This is useful when you want to create objects that are uniquely identified by their key fields.

```java
Person person = new Person( "John", "Doe" );
```

--------------------------------

### DRL Example: Delete Applicant

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Example of using the `delete` method to remove an `Applicant` object from the Drools rule engine.

```drl
delete( Applicant );
```

--------------------------------

### Time Construction Examples

Source: https://docs.drools.org/latest/drools-docs/drools/DMN/index.html

Illustrates constructing time values using the `time()` function in FEEL. Supports various formats including time with timezone offsets and UTC.

```FEEL
time( "04:25:12" )
```

```FEEL
time( "14:10:00+02:00" )
```

```FEEL
time( "22:35:40.345-05:00" )
```

```FEEL
time( "15:00:30z" )
```

--------------------------------

### Hierarchy Text Output Example

Source: https://docs.drools.org/latest/drools-docs/drools/experimental-features/index.html

Example of hierarchy text output from TextReporter, indicating changed rules with [*] and impacted rules with [+].

```text
--- toHierarchyText ---
Inventory shortage[+]
PriceCheck_11[*]
  StatusCheck_12[+]
  (Inventory shortage)
  StatusCheck_13[+]
  StatusCheck_11[+]
    (PriceCheck_11)
```

--------------------------------

### Creating, Setting, Updating, and Clearing SingletonStore

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Shows how to use a SingletonStore to manage a single 'Measurement' object. Demonstrates setting, updating, and clearing the value, with notifications.

```java
SingletonStore<Measurement> measurement = DataSource.createSingleton();
Measurement m1 = new Measurement("color", "red");
// Add value `m1` and notify all subscribers
measurement.set(m1);
measure.setValue("blue");
// Notify all subscribers that the value has changed
measurement.update();

Measurement m2 = new Measurement("color", "green");
// Overwrite contained value with `m2` and notify all subscribers
measurement.set(m2);
measure2.setValue("black");
// Notify all subscribers that the value has changed
measurement.update();

// Clear store and notify all subscribers
measurement.clear();
```

--------------------------------

### DRL Example: Insert New Applicant

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Example of using the `insert` method to add a new `Applicant` object to the working memory.

```drl
insert( new Applicant() );
```

--------------------------------

### DRL Example: Update Loan Application

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Example of using the `update` method to change the amount of a loan application fact and then notify the engine.

```drl
$application.setAmount( 100 );
update( $application );
```

--------------------------------

### Days and Time Duration Construction Examples

Source: https://docs.drools.org/latest/drools-docs/drools/DMN/index.html

Shows how to construct days and time duration values using the `duration()` function. Supports ISO 8601 format for days, hours, minutes, and seconds.

```FEEL
duration( "P1DT23H12M30S" )
```

```FEEL
duration( "P23D" )
```

```FEEL
duration( "PT12H" )
```

```FEEL
duration( "PT35M" )
```

--------------------------------

### DRL Example: Modify Loan Application

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Example of using the `modify` method to update the amount and approval status of a loan application fact.

```drl
modify( $application ) {
        setAmount( 100 ),
        setApproved ( true )
}
```

--------------------------------

### Implement DRL File with Standard DRL Syntax

Source: https://docs.drools.org/latest/drools-docs/drools/migration-guide/index.html

Alternatively, use standard DRL syntax to specify the data source as an entry point. The object type must be explicitly stated.

```drl
$l: LoanApplication( applicant.age >= 20, deposit >= 1000, amount ⇐ maxAmount ) from entry-point loanApplications
```

--------------------------------

### Date Construction Example

Source: https://docs.drools.org/latest/drools-docs/drools/DMN/index.html

Shows how to construct a date value using the built-in `date()` function in FEEL. Dates follow the 'YYYY-MM-DD' format.

```FEEL
date( "2017-06-23" )
```

--------------------------------

### Example ReteDumper Output

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Shows sample output from ReteDumper, mapping node identifiers to rule names. This helps in pinpointing which rule corresponds to a performance metric.

```text
[ AccumulateNode(8) ] : [Collect expensive orders combination]
...
```

--------------------------------

### DRL Example: Logically Insert New Applicant

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Example of using the `insertLogical` method to add a new `Applicant` object logically to the working memory.

```drl
insertLogical( new Applicant() );
```

--------------------------------

### Sample kmodule.xml Configuration

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Defines two KieBases with different configurations and multiple KieSessions, including custom operators, listeners, and work item handlers.

```xml
<kmodule xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
        xmlns="http://www.drools.org/xsd/kmodule">
  <configuration>
    <property key="drools.evaluator.supersetOf" value="org.mycompany.SupersetOfEvaluatorDefinition"/>
  </configuration>
  <kbase name="KBase1" default="true" eventProcessingMode="cloud" equalsBehavior="equality" declarativeAgenda="enabled" packages="org.domain.pkg1">
    <ksession name="KSession2_1" type="stateful" default="true"/>
    <ksession name="KSession2_2" type="stateless" default="false" beliefSystem="jtms"/>
  </kbase>
  <kbase name="KBase2" default="false" eventProcessingMode="stream" equalsBehavior="equality" declarativeAgenda="enabled" packages="org.domain.pkg2, org.domain.pkg3" includes="KBase1">
    <ksession name="KSession3_1" type="stateful" default="false" clockType="realtime">
      <fileLogger file="drools.log" threaded="true" interval="10"/>
      <workItemHandlers>
        <workItemHandler name="name" type="org.domain.WorkItemHandler"/>
      </workItemHandlers>
      <calendars>
        <calendar name="monday" type="org.domain.Monday"/>
      </calendars>
      <listeners>
        <ruleRuntimeEventListener type="org.domain.RuleRuntimeListener"/>
        <agendaEventListener type="org.domain.FirstAgendaListener"/>
        <agendaEventListener type="org.domain.SecondAgendaListener"/>
        <processEventListener type="org.domain.ProcessListener"/>
      </listeners>
    </ksession>
  </kbase>
</kmodule>
```

--------------------------------

### Example cURL Request to Find Approved Loans

Source: https://docs.drools.org/latest/drools-docs/drools/migration-guide/index.html

Example cURL command to invoke the REST endpoint with JSON payload for loan application evaluation.

```bash
curl -X POST -H 'Accept: application/json' -H 'Content-Type: application/json' -d '{"maxAmount":5000,
"loanApplications":[
{"id":"ABC10001","amount":2000,"deposit":1000,"applicant":{"age":45,"name":"John"}}, {"id":"ABC10002","amount":5000,"deposit":100,"applicant":{"age":25,"name":"Paul"}}, {"id":"ABC10015","amount":1000,"deposit":100,"applicant":{"age":12,"name":"George"}}
]}' http://localhost:8080/find-approved
```

--------------------------------

### MVEL Invalid Coercion Example (Non-Executable Model)

Source: https://docs.drools.org/latest/drools-docs/drools/migration-guide/index.html

Shows an example where the non-executable model coerces an int to a Long, which would fail in the executable model.

```java
rule Rule1
dialect "mvel"
when
  $f : Fact()
then
  $f.setWrapperLong(10);
end
```

--------------------------------

### EventA starts EventB

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Matches if EventA and EventB start at the same time, and EventA ends before EventB ends. This operator can also be expressed using timestamp comparisons.

```drl
$eventA : EventA(this starts $eventB)
```

--------------------------------

### Execute Stateless Session with Commands

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Shows how to use CommandFactory to create and execute a list of commands, such as inserting multiple Person objects into the session.

```java
List<Command> cmds = new ArrayList<Command>();  __**(3)**
cmds.add(CommandFactory.newInsert(new Person("Mr John Smith"), "mrSmith"));
cmds.add(CommandFactory.newInsert(new Person("Mr John Doe"), "mrDoe"));
```

--------------------------------

### Instantiate and Execute a Rule Unit Instance

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Use `RuleUnitProvider` to create a `RuleUnitInstance` for executing rules. Remember to dispose of the instance when done.

```java
public void test() {
        MeasurementUnit measurementUnit = new MeasurementUnit();

        RuleUnitInstance<MeasurementUnit> instance = RuleUnitProvider.get().createRuleUnitInstance(measurementUnit);
        try {
            measurementUnit.getMeasurements().add(new Measurement("color", "red"));
            ...

            List<Measurement> queryResult = instance.executeQuery("FindColor").stream().map(tuple -> (Measurement) tuple.get("$m")).collect(toList());
            ...

        } finally {
            instance.dispose();
        }
    }
```

--------------------------------

### Execute Rule Unit Instance

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

This snippet shows how to instantiate a RuleUnit, add data, create a RuleUnitInstance, fire rules, and assert the results. It demonstrates the runtime execution of rules defined via the Rule Unit DSL.

```java
    public void helloWorld() {
        HelloWorldUnit unit = new HelloWorldUnit();
        unit.getStrings().add("Hello World");

        RuleUnitInstance<HelloWorldUnit> unitInstance = RuleUnitProvider.get().createRuleUnitInstance(unit);

        assertThat(unitInstance.fire()).isEqualTo(2);
        assertThat(unit.getResults()).containsExactlyInAnyOrder("it worked!", "it also worked with HELLO WORLD");

        unit.getResults().clear();
        unit.getInts().add(11);
        assertThat(unitInstance.fire()).isEqualTo(1);
        assertThat(unit.getResults()).containsExactly("String 'Hello World' is 11 characters long");

        unitInstance.close();
    }
```

--------------------------------

### Example calendar attributes

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

These examples show how to use the 'calendars' attribute with a Quartz cron expression to exclude non-business hours or use a pre-registered calendar name.

```drl
// Exclude non-business hours
calendars "* * 0-7,18-23 ? * *"
```

```drl
// Weekdays only, as registered in the KIE session
calendars "weekday"
```

--------------------------------

### Register and Start KieScanner with File System Repository

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

This snippet illustrates how to configure a KieScanner to monitor a local file system folder for kjar updates. The folder must contain jar files named according to the Maven convention.

```java
KieServices kieServices = KieServices.Factory.get();
KieScanner kScanner = kieServices.newKieScanner( kContainer, "/myrepo/kjars" );
```

--------------------------------

### EventA met by EventB

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Matches if EventB ends at the same time EventA starts. This is the reverse of the 'meets' operator. It supports an optional time parameter for the maximum distance between the end of EventB and the start of EventA.

```drl
$eventA : EventA(this metby $eventB)
```

--------------------------------

### EventA meets EventB

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Matches if EventA ends at the same time EventB starts. This operator can also accept an optional time parameter to define the maximum allowed time between the end of EventA and the start of EventB.

```drl
$eventA : EventA(this meets $eventB)
```

--------------------------------

### Application Code for Live Query with Event Listener

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Sets up a ViewChangedEventListener to monitor updates, removals, and additions to a live query. It then opens the 'colors' live query with specific parameters ('red', 'blue') and demonstrates how to dispose of the query.

```java
final List updated = new ArrayList();
final List removed = new ArrayList();
final List added = new ArrayList();

ViewChangedEventListener listener = new ViewChangedEventListener() {
 public void rowUpdated(Row row) {
  updated.add( row.get( "$price" ) );
 }

 public void rowRemoved(Row row) {
  removed.add( row.get( "$price" ) );
 }

 public void rowAdded(Row row) {
  added.add( row.get( "$price" ) );
 }
};

// Open the live query:
LiveQuery query = ksession.openLiveQuery( "colors",
                                          new Object[] { "red", "blue" },
                                          listener );
...
...

// Terminate the live query:
query.dispose()
```

--------------------------------

### Event A occurs before Event B with time range

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Matches if EventA finishes between 3m30s and 4m before EventB starts. This pattern is not matched if EventA finishes earlier than 3m30s or later than 4m before EventB starts.

```java
$eventA : EventA(this before[3m30s, 4m] $eventB)
```

--------------------------------

### Utilize and Run KieModule with Meta Models (Java)

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

This Java code demonstrates building a KieModule by defining its kmodule.xml meta-model programmatically. It includes setting up ReleaseIds, generating POM XML, defining KieBases and KieSessions, and then building and running the module.

```java
KieServices ks = KieServices.Factory.get();
KieFileSystem kfs = ks.newKieFileSystem();

Resource ex1Res = ks.getResources().newFileSystemResource(getFile("named-kiesession"));
Resource ex2Res = ks.getResources().newFileSystemResource(getFile("kiebase-inclusion"));

ReleaseId rid = ks.newReleaseId("org.drools", "kiemodulemodel-example", "6.0.0-SNAPSHOT");
kfs.generateAndWritePomXML(rid);

KieModuleModel kModuleModel = ks.newKieModuleModel();
kModuleModel.newKieBaseModel("kiemodulemodel")
            .addInclude("kiebase1")
            .addInclude("kiebase2")
            .newKieSessionModel("ksession6");

kfs.writeKModuleXML(kModuleModel.toXML());
kfs.write("src/main/resources/kiemodulemodel/HAL6.drl", getRule());

KieBuilder kb = ks.newKieBuilder(kfs);
b.setDependencies(ex1Res, ex2Res);
b.buildAll(); // kieModule is automatically deployed to KieRepository if successfully built.
if (kb.getResults().hasMessages(Level.ERROR)) {
    throw new RuntimeException("Build Errors:\n" + kb.getResults().toString());
}

KieContainer kContainer = ks.newKieContainer(rid);

KieSession kSession = kContainer.newKieSession("ksession6");
kSession.setGlobal("out", out);

Object msg1 = createMessage(kContainer, "Dave", "Hello, HAL. Do you read me, HAL?");
kSession.insert(msg1);
kSession.fireAllRules();

Object msg2 = createMessage(kContainer, "Dave", "Open the pod bay doors, HAL.");
kSession.insert(msg2);
kSession.fireAllRules();

Object msg3 = createMessage(kContainer, "Dave", "What's the problem?");
kSession.insert(msg3);
kSession.fireAllRules();
javaCopied!
```

--------------------------------

### Event A occurs after Event B with time range

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Matches if EventA starts between 3m30s and 4m after EventB finishes. This pattern is not matched if EventA starts earlier than 3m30s or later than 4m after EventB finishes.

```java
$eventA : EventA(this after[3m30s, 4m] $eventB)
```

--------------------------------

### Instantiate Stateful KieSession and Insert Initial Data

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Creates a new stateful KieSession from the KieContainer and inserts initial room and sprinkler facts.

```java
KieSession ksession = kContainer.newKieSession();

String[] names = new String[]{"kitchen", "bedroom", "office", "livingroom"};
Map<String,Room> name2room = new HashMap<String,Room>();
for( String name: names ){
    Room room = new Room( name );
    name2room.put( name, room );
    ksession.insert( room );
    Sprinkler sprinkler = new Sprinkler( room );
    ksession.insert( sprinkler );
}

ksession.fireAllRules();
```

--------------------------------

### Timer attribute with start, end, and repeat-limit

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

This snippet shows a timer attribute with optional start, end, and repeat-limit parameters. The timer will stop when either the end date is reached or the repeat limit is met.

```drl
timer (int: 30s 1h; start=3-JAN-2020, end=4-JAN-2020, repeat-limit=50)
```

--------------------------------

### Build Maven Project

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Builds the Maven project to generate a JAR file in the target folder, which can then be referenced as a File resource.

```bash
mvn install
Copied!

```

--------------------------------

### Event Includes Another Event's Timeframe

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Checks if event $eventA's time frame completely encompasses event $eventB. The start and end times of $eventB must fall between the start and end times of $eventA.

```drools
$eventA : EventA(this includes $eventB)
```

```drools
$eventA.startTimestamp < $eventB.startTimestamp <= $eventB.endTimestamp < $eventA.endTimestamp
```

--------------------------------

### Build Drools with Tests

Source: https://docs.drools.org/latest/drools-docs/drools/introduction/index.html

Run this command to build the Drools project and execute all associated tests.

```bash
mvn clean install
```

--------------------------------

### Build KieModule with Impact Analysis

Source: https://docs.drools.org/latest/drools-docs/drools/experimental-features/index.html

Create a KieFileSystem, build the KieModule using KieBuilder, and specify ImpactAnalysisProject.class to obtain the AnalysisModel.

```java
// set up KieFileSystem
      ...
      KieBuilder kieBuilder = KieServices.Factory.get().newKieBuilder(kfs).buildAll(ImpactAnalysisProject.class);
      ImpactAnalysisKieModule analysisKieModule = (ImpactAnalysisKieModule) kieBuilder.getKieModule();
      AnalysisModel analysisModel = analysisKieModule.getAnalysisModel();
```

--------------------------------

### Configure Default KieSession with kmodule.xml

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

An empty kmodule.xml file is used to create a default KieBase that includes all resources on the classpath. This is useful when you have a single KieBase and want to access its default KieSession without explicit naming.

```xml
<kmodule xmlns="http://www.drools.org/xsd/kmodule"> </kmodule>
```

--------------------------------

### EventA overlaps EventB

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Matches if EventA starts before EventB and ends while EventB is occurring, but before EventB ends. This operator can take one or two parameters to define the maximum or a range of distances between EventB's start and EventA's end.

```drl
$eventA : EventA(this overlaps $eventB)
```

--------------------------------

### KIE Base Configuration

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Example configuration for a KIE base in a kmodule.xml file. This defines a KIE base named 'KBase2' with specific packages and includes another KIE base.

```xml
<kmodule>
  ...
  <kbase name="KBase2" default="false" eventProcessingMode="stream" equalsBehavior="equality" declarativeAgenda="enabled" packages="org.domain.pkg2, org.domain.pkg3" includes="KBase1">
    ...
  </kbase>
  ...
</kmodule>
```

--------------------------------

### Event Contained Within Another Event's Timeframe

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Checks if event $eventA occurs entirely within the time frame of event $eventB. The start and end times of $eventA must fall between the start and end times of $eventB.

```drools
$eventA : EventA(this during $eventB)
```

```drools
$eventB.startTimestamp < $eventA.startTimestamp <= $eventA.endTimestamp < $eventB.endTimestamp
```

--------------------------------

### Java Application with EntryPoint Object

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

This Java code demonstrates how to obtain an EntryPoint object from a KieSession and insert facts into a specific entry point named 'ATM Stream'. Rules referencing this entry point will then evaluate against these inserted facts.

```java
import org.kie.api.runtime.KieSession;
import org.kie.api.runtime.rule.EntryPoint;

// Create your KIE base and KIE session as usual.
KieSession session = ...

// Create a reference to the entry point.
EntryPoint atmStream = session.getEntryPoint("ATM Stream");

// Start inserting your facts into the entry point.
atmStream.insert(aWithdrawRequest);
```

--------------------------------

### EventA met by EventB with time constraint

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Matches if EventA starts within 5 seconds of EventB ending. The absolute difference between EventA's start timestamp and EventB's end timestamp must be less than or equal to 5 seconds.

```drl
$eventA : EventA(this metby[5s] $eventB)
```

--------------------------------

### EventA meets EventB with time constraint

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Matches if EventA ends within 5 seconds of EventB starting. The absolute difference between EventB's start timestamp and EventA's end timestamp must be less than or equal to 5 seconds.

```drl
$eventA : EventA(this meets[5s] $eventB)
```

--------------------------------

### Execute Collection with InsertElements Command

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

This snippet demonstrates executing a collection by wrapping it in an InsertElements command for the StatelessKieSession.

```java
ksession.execute( CommandFactory.newInsertElements( collection ) );
```

--------------------------------

### Creating a KieContainer from the Classpath

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

To trigger the building of Kie artifacts, create a KieContainer. This example shows how to create a KieContainer that reads files to be built from the classpath.

```java
KieServices kieServices = KieServices.Factory.get();
KieContainer kContainer = kieServices.getKieClasspathContainer();
```

--------------------------------

### Example DRL Rule Unit File for Loan Application

Source: https://docs.drools.org/latest/drools-docs/drools/language-reference/index.html

Declares a Drools rule unit named MortgageRules, imports necessary APIs, defines data stores for fact types, and includes two example rules: 'Bankruptcy history' and 'Underage'.

```drl
package org.mortgages;
unit MortgageRules;

import org.drools.ruleunits.api.RuleUnitData;
import org.drools.ruleunits.api.DataStore;

declare MortgageRules extends RuleUnitData
  bankruptcies: DataStore<Bankruptcy>
  applicants: DataStore<Applicant>
  loanApplications: DataStore<LoanApplication>
end

rule "Bankruptcy history"
	salience 10
	when
    $a : /loanApplications[ applicantName: applicant ]
    exists (/bankruptcies[ name == applicantName, yearOfOccurrence > 1990 || amountOwed > 100000 ])
	then
		$a.setApproved( false );
		$a.setExplanation( "has been bankrupt" );
		loanApplications.remove( $a );
end

rule "Underage"
	salience 15
	when
    /applicants[ applicantName : name, age < 21 ]
    $application : /loanApplications[ applicant == applicantName ]
	then
		$application.setApproved( false );
		$application.setExplanation( "Underage" );
		loanApplications.remove( $a );
end
```

--------------------------------

### Creating, Adding, Updating, and Removing from DataStore

Source: https://docs.drools.org/latest/drools-docs/drools/KIE/index.html

Illustrates the usage of DataStore for managing 'Measurement' objects. Includes adding, updating, and removing data, with notifications to subscribers.

```java
DataStore<Measurement> measurements = DataSource.createStore();
Measurement measurement = new Measurement("color", "red");
// Add value and notify all subscribers
DataHandle mHandle = measurements.add(measurement);
measure.setValue("blue");
// Notify all subscribers that the value referenced by `mHandle` has changed
measurements.update(mHandle, measurement);
// Remove value referenced by `mHandle` and notify all subscribers
measurements.remove(mHandle);
```

--------------------------------

### Event A occurs before Event B with negative time range

Source: https://docs.drools.org/latest/drools-docs/drools/rule-engine/index.html

Matches if EventA finishes within a negative time range relative to EventB's start time. This allows for scenarios where EventA might finish after EventB starts, within specified bounds.

```java
$eventA : EventA(this before[-3m30s, -2m] $eventB)
```
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