Drools 没有按预期工作。 规则不适用

Question

􏰧􏰉􏰙􏰑Good afternoon, I'm a rookie with drools, I'm trying to learn by making an example.

My example deals with the classic problem of applying rules in order to tax some products of an order, so I have two classes, Order and Product, something like that:

Order class

import java.util.ArrayList;
import java.util.List;
import java.util.UUID;

public class Order {

private String id;
private List<Product> products;
private double totalPrize;
private double totalTaxes;

public Order() {
    super();
    this.id=UUID.randomUUID().toString();
    this.products = new ArrayList<Product>();
    this.totalPrize = 0d;
    this.totalTaxes = 0d;

}

public List<Product> getProducts() {
    return products;
}

public void addProduct(Product p) {
    this.products.add(p);
}
public double getTotalPrize() {
    return totalPrize;
}
public void setTotalPrize(double totalPrize) {
    this.totalPrize += totalPrize;
}
public double getTotalTaxes() {
    return totalTaxes;
}
public void setTotalTaxes(double totalTaxes) {
    this.totalTaxes += totalTaxes;
}

@Override
public String toString() {
    StringBuilder builder = new StringBuilder();
    builder.append("Order [id=").append(id).append(", products=").append(products).append(", totalPrize=")
            .append(totalPrize).append(", totalTaxes=").append(totalTaxes).append("]");
    return builder.toString();
}


}

Product class

import java.util.UUID;

public class Product {

private String id;
private String description;
private double prize;
private boolean imported;
private boolean tax_exempt;
private double sale_tax;

public Product(String description, double prize) {
    super();
    this.id=UUID.randomUUID().toString();
    this.description = description;
    this.prize = prize;
    this.tax_exempt = description.matches("(.*)book(.*)") || 
                      description.matches("(.*)food(.*)") || 
                      description.matches("(.*)medical(.*)");

    this.imported = description.matches("(.*)imported(.*)");

}

public double getPrize() {
    return prize;
}

public boolean isImported() {
    return imported;
}


public boolean isTax_exempt() {
    return tax_exempt;
}

public double getSale_tax() {
    return sale_tax;
}

public void setSale_tax(double sale_tax) {
    this.sale_tax = sale_tax;
}

@Override
public String toString() {
    StringBuilder builder = new StringBuilder();
    builder.append("Product [id=").append(id).append(", description=").append(description).append(", prize=")
            .append(prize).append(", imported=").append(imported).append(", tax_exempt=").append(tax_exempt)
            .append(", sale_tax=").append(sale_tax).append("]");
    return builder.toString();
}

}

Order has a list of products, if the product is imported, i will apply a tax of 5%. I apply a product to be taxed using a boolean.

this is how i create the order and chain it to kSession:

  //This is part of main mathod. 
  public static Order createOrder2() {
    /*
     * 
     * 1 imported box of chocolate 10.00
     * 1 imported bottle of perfume 47.50
     * */
    Product p1 = new Product("imported food box of chocolate", 10.00d); //exempted and imported
    Product p2 = new Product("imported bottle of perfume",14.99); //not exempted imported

    Order order = new Order();
    order.addProduct(p1);
    order.addProduct(p2);

    return order;
}


@Inject
@KSession
private KieSession kSession;

// instantiating order2 from above method.

kSession.insert(order2);
kSession.fireAllRules();
// end of main class

This is part of the rules file

rule "Applying taxes to imported products."
when
    $order: Order()
    $products: Product() from $order.getProducts()
    $product: Product($products.isImported())
then
    $product.setSale_tax($product.getPrize() *5d/100);  
    $order.setTotalPrize($product.getSale_tax() + $product.getPrize());
    $order.setTotalTaxes($product.getSale_tax());
    System.out.println($order.toString());
    System.out.println($order.getTotalPrize()); 
    System.out.println($order.getTotalTaxes());
end

I insert an order to kSession and fired the rules and when i run a test method, i got this output in terminal and test fails.

Test method:

@Test
public void should_apply_rules_to_order1_exempted_imported_not_imported() {
    //GIVEN
    Assert.assertNotNull(kSession);
    final Order order1 = Utilities.createOrder1();
    //WHEN
    kSession.insert(order1);

    //THEN
    Assert.assertEquals(1, kSession.fireAllRules());
    Assert.assertEquals("Shoud be equals...",29.83d, order1.getTotalPrize(),0d);
    Assert.assertEquals("Shoud be equals...",1.50d, order1.getTotalTaxes(),0d);
}

This is the pom.xml file:

<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>com.aironman.test.rumbo</groupId>
<artifactId>TaxPlanner</artifactId>
<version>0.0.1-SNAPSHOT</version>
<description>A pet test project</description>

<properties>
    <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
    <kie.version>6.3.0.Final</kie.version>
    <junit.version>4.11</junit.version>
    <cdi.version>1.2</cdi.version>
    <weld.version>2.3.0.Final</weld.version>
    <maven.compiler.source>1.8</maven.compiler.source>
    <maven.compiler.target>1.8</maven.compiler.target>
</properties>

<dependencyManagement>
    <dependencies>
        <dependency>
            <groupId>org.jboss.arquillian</groupId>
            <artifactId>arquillian-bom</artifactId>
            <version>1.1.10.Final</version>
            <scope>import</scope>
            <type>pom</type>
        </dependency>
    </dependencies>
</dependencyManagement>

<dependencies>
    <dependency>
        <groupId>org.kie</groupId>
        <artifactId>kie-api</artifactId>
        <version>${kie.version}</version>
    </dependency>
    <dependency>
        <groupId>org.drools</groupId>
        <artifactId>drools-compiler</artifactId>
        <version>${kie.version}</version>
    </dependency>
    <dependency>
        <groupId>org.drools</groupId>
        <artifactId>drools-core</artifactId>
        <version>${kie.version}</version>
    </dependency>
    <dependency>
        <groupId>javax.enterprise</groupId>
        <artifactId>cdi-api</artifactId>
        <version>${cdi.version}</version>
    </dependency>
    <dependency>
        <groupId>org.jboss.weld.se</groupId>
        <artifactId>weld-se-core</artifactId>
        <version>${weld.version}</version>
    </dependency>
    <dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>${junit.version}</version>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.jboss.arquillian.junit</groupId>
        <artifactId>arquillian-junit-container</artifactId>
        <scope>test</scope>
    </dependency>
    <dependency>
        <groupId>org.jboss.arquillian.container</groupId>
        <artifactId>arquillian-weld-se-embedded-1.1</artifactId>
        <version>1.0.0.CR9</version>
        <scope>test</scope>
    </dependency>
</dependencies>

Two questions, please, what do am i doing wrong in order drools is not applying the rule, and how can i recover the object from the engine once rules are applied?

@ioannis-barakos, i saw in a previous post you helped another guy with similar problem, could you help me?

Answer 1

You only have an Order in working memory, not a Product so your rule doesn't trigger. The rule will only trigger when all of the conditions on the left hand side (the "when" clause) match.

The following rule should be more like you expect:

dialect "mvel"

rule "Applying taxes to imported products."
when

  // Take the order from working memory and get the product list from it
  $order: Order( $products: products != null )

  // Get only the imported products
  $product: Product( isImported == true ) from $products
then
  $product.setSale_tax($product.getPrize() * (5d/100));  
  $order.setTotalPrize($product.getSale_tax() + $product.getPrize());
  $order.setTotalTaxes($product.getSale_tax());
  System.out.println($order.toString());
  System.out.println($order.getTotalPrize()); 
  System.out.println($order.getTotalTaxes());
end

The first thing we do is get the product list from the order and alias it to $products . Then we get the imported products from that list -- notice the from $products .

In your original, you were just calling $product: Product( ... ) which says "get me a product that looks like this from working memory. Since you didn't have anything in working memory, it didn't work.

(Also the way you were getting the $products from the order was a little wonky... not sure what you were trying to do there.)