第7章 DMN model execution

You can create or import DMN files in your Red Hat Decision Manager project using Business Central or package the DMN files as part of your project knowledge JAR (KJAR) file without Business Central. After you implement your DMN files in your Red Hat Decision Manager project, you can execute the DMN decision service by deploying the KIE container that contains it to KIE Server for remote access or by manipulating the KIE container directly as a dependency of the calling application. Other options for creating and deploying DMN knowledge packages are also available, and most are similar for all types of knowledge assets, such as DRL files or process definitions.

For information about including external DMN assets with your project packaging and deployment method, see Packaging and deploying a Red Hat Decision Manager project.

7.1. Embedding a DMN call directly in a Java application

A KIE container is local when the knowledge assets are either embedded directly into the calling program or are physically pulled in using Maven dependencies for the KJAR. You typically embed knowledge assets directly into a project if there is a tight relationship between the version of the code and the version of the DMN definition. Any changes to the decision take effect after you have intentionally updated and redeployed the application. A benefit of this approach is that proper operation does not rely on any external dependencies to the run time, which can be a limitation of locked-down environments.

Using Maven dependencies enables further flexibility because the specific version of the decision can dynamically change, (for example, by using a system property), and it can be periodically scanned for updates and automatically updated. This introduces an external dependency on the deploy time of the service, but executes the decision locally, reducing reliance on an external service being available during run time.

Prerequisites

  • You have built the DMN project as a KJAR artifact and deployed it to a Maven repository, or you have included your DMN assets as part of your project classpath. Ideally, you have built the DMN project as an executable model for more efficient execution: 

    mvn clean install -DgenerateDMNModel=yes

    For more information about project packaging and deployment and executable models, see Packaging and deploying a Red Hat Decision Manager project.

Procedure

  1. In your client application, add the following dependencies to the relevant classpath of your Java project: 

    <!-- Required for the DMN runtime API -->
<dependency>
  <groupId>org.kie</groupId>
  <artifactId>kie-dmn-core</artifactId>
  <version>${rhdm.version}</version>
</dependency>

<!-- Required if not using classpath KIE container -->
<dependency>
  <groupId>org.kie</groupId>
  <artifactId>kie-ci</artifactId>
  <version>${rhdm.version}</version>
</dependency>

    The <version> is the Maven artifact version for Red Hat Decision Manager currently used in your project (for example, 7.48.0.Final-redhat-00004).

    注記

    Instead of specifying a Red Hat Decision Manager <version> for individual dependencies, consider adding the Red Hat Business Automation bill of materials (BOM) dependency to your project pom.xml file. The Red Hat Business Automation BOM applies to both Red Hat Decision Manager and Red Hat Process Automation Manager. When you add the BOM files, the correct versions of transitive dependencies from the provided Maven repositories are included in the project.

    Example BOM dependency: 

    <dependency>
  <groupId>com.redhat.ba</groupId>
  <artifactId>ba-platform-bom</artifactId>
  <version>7.10.0.redhat-00004</version>
  <scope>import</scope>
  <type>pom</type>
</dependency>

    For more information about the Red Hat Business Automation BOM, see What is the mapping between RHDM product and maven library version?.

  2. Create a KIE container from classpath or ReleaseId: 

    KieServices kieServices = KieServices.Factory.get();

ReleaseId releaseId = kieServices.newReleaseId( "org.acme", "my-kjar", "1.0.0" );
KieContainer kieContainer = kieServices.newKieContainer( releaseId );

    Alternative option: 

    KieServices kieServices = KieServices.Factory.get();

KieContainer kieContainer = kieServices.getKieClasspathContainer();

  3. Obtain DMNRuntime from the KIE container and a reference to the DMN model to be evaluated, by using the model namespace and modelName: 

    DMNRuntime dmnRuntime = KieRuntimeFactory.of(kieContainer.getKieBase()).get(DMNRuntime.class);

String namespace = "http://www.redhat.com/_c7328033-c355-43cd-b616-0aceef80e52a";
String modelName = "dmn-movieticket-ageclassification";

DMNModel dmnModel = dmnRuntime.getModel(namespace, modelName);

  4. Execute the decision services for the desired model: 

    DMNContext dmnContext = dmnRuntime.newContext();  1

for (Integer age : Arrays.asList(1,12,13,64,65,66)) {
    dmnContext.set("Age", age);  2
    DMNResult dmnResult =
        dmnRuntime.evaluateAll(dmnModel, dmnContext);  3

    for (DMNDecisionResult dr : dmnResult.getDecisionResults()) {  4
        log.info("Age: " + age + ", " +
                 "Decision: '" + dr.getDecisionName() + "', " +
                 "Result: " + dr.getResult());
  }
}
    1
    Instantiate a new DMN Context to be the input for the model evaluation. Note that this example is looping through the Age Classification decision multiple times.
    2
    Assign input variables for the input DMN context.
    3
    Evaluate all DMN decisions defined in the DMN model.
    4
    Each evaluation may result in one or more results, creating the loop.

    This example prints the following output: 

    Age 1 Decision 'AgeClassification' : Child
Age 12 Decision 'AgeClassification' : Child
Age 13 Decision 'AgeClassification' : Adult
Age 64 Decision 'AgeClassification' : Adult
Age 65 Decision 'AgeClassification' : Senior
Age 66 Decision 'AgeClassification' : Senior

    If the DMN model was not previously compiled as an executable model for more efficient execution, you can enable the following property when you execute your DMN models: 

    -Dorg.kie.dmn.compiler.execmodel=true