Chapter 4. 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.

4.1. 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

  • KIE Server is installed and configured, including a known user name and credentials for a user with the kie-server role. For installation options, see Planning a Red Hat Decision Manager installation.
  • You have built the DMN project as a KJAR artifact and deployed it to KIE Server. 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, 7.39.0.Final-redhat-00005).

    Note

    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>7.8.0.redhat-00005</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

4.2. Executing a DMN service using the KIE Server Java client API

The KIE Server Java client API provides a lightweight approach to invoking a remote DMN service either through the REST or JMS interfaces of KIE Server. This approach reduces the number of runtime dependencies necessary to interact with a KIE base. Decoupling the calling code from the decision definition also increases flexibility by enabling them to iterate independently at the appropriate pace.

For more information about the KIE Server Java client API, see Interacting with Red Hat Decision Manager using KIE APIs.

Prerequisites

  • KIE Server is installed and configured, including a known user name and credentials for a user with the kie-server role. For installation options, see Planning a Red Hat Decision Manager installation.
  • You have built the DMN project as a KJAR artifact and deployed it to KIE Server. 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.

  • You have the ID of the KIE container containing the DMN model. If more than one model is present, you must also know the model namespace and model name of the relevant model.

Procedure

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

    <!-- Required for the KIE Server Java client API -->
    <dependency>
      <groupId>org.kie.server</groupId>
      <artifactId>kie-server-client</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, 7.39.0.Final-redhat-00005).

    Note

    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>7.8.0.redhat-00005</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. Instantiate a KieServicesClient instance with the appropriate connection information.

    Example:

    KieServicesConfiguration conf =
        KieServicesFactory.newRestConfiguration(URL, USER, PASSWORD); 1
    
    conf.setMarshallingFormat(MarshallingFormat.JSON);  2
    
    KieServicesClient kieServicesClient = KieServicesFactory.newKieServicesClient(conf);
    1
    The connection information:
    • Example URL: http://localhost:8080/kie-server/services/rest/server
    • The credentials should reference a user with the kie-server role.
    2
    The Marshalling format is an instance of org.kie.server.api.marshalling.MarshallingFormat. It controls whether the messages will be JSON or XML. Options for Marshalling format are JSON, JAXB, or XSTREAM.
  3. Obtain a DMNServicesClient from the KIE server Java client connected to the related KIE Server by invoking the method getServicesClient() on the KIE server Java client instance:

    DMNServicesClient dmnClient = kieServicesClient.getServicesClient(DMNServicesClient.class );

    The dmnClient can now execute decision services on KIE Server.

  4. Execute the decision services for the desired model.

    Example:

    for (Integer age : Arrays.asList(1,12,13,64,65,66)) {
        DMNContext dmnContext = dmnClient.newContext(); 1
        dmnContext.set("Age", age);  2
        ServiceResponse<DMNResult> serverResp =   3
            dmnClient.evaluateAll($kieContainerId,
                                  $modelNamespace,
                                  $modelName,
                                  dmnContext);
    
        DMNResult dmnResult = serverResp.getResult();  4
        for (DMNDecisionResult dr : dmnResult.getDecisionResults()) {
            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 the DMN Decisions defined in the DMN model:
    • $kieContainerId is the ID of the container where the KJAR containing the DMN model is deployed
    • $modelNamespace is the namespace for the model.
    • $modelName is the name for the model.
    4
    The DMN Result object is available from the server response.

    At this point, the dmnResult contains all the decision results from the evaluated DMN model.

    You can also execute only a specific DMN decision in the model by using alternative methods of the DMNServicesClient.

    Note

    If the KIE container only contains one DMN model, you can omit $modelNamespace and $modelName because the KIE Server API selects it by default.

4.3. Executing a DMN service using the KIE Server REST API

Directly interacting with the REST endpoints of KIE Server provides the most separation between the calling code and the decision logic definition. The calling code is completely free of direct dependencies, and you can implement it in an entirely different development platform such as Node.js or .NET. The examples in this section demonstrate Nix-style curl commands but provide relevant information to adapt to any REST client.

For more information about the KIE Server REST API, see Interacting with Red Hat Decision Manager using KIE APIs.

Prerequisites

  • KIE Server is installed and configured, including a known user name and credentials for a user with the kie-server role. For installation options, see Planning a Red Hat Decision Manager installation.
  • You have built the DMN project as a KJAR artifact and deployed it to KIE Server. 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.

  • You have the ID of the KIE container containing the DMN model. If more than one model is present, you must also know the model namespace and model name of the relevant model.

Procedure

  1. Determine the base URL for accessing the KIE Server REST API endpoints. This requires knowing the following values (with the default local deployment values as an example):

    • Host (localhost)
    • Port (8080)
    • Root context (kie-server)
    • Base REST path (services/rest/)

    Example base URL in local deployment:

    http://localhost:8080/kie-server/services/rest/

  2. Determine user authentication requirements.

    When users are defined directly in the KIE Server configuration, HTTP Basic authentication is used and requires the user name and password. Successful requests require that the user have the kie-server role.

    The following example demonstrates how to add credentials to a curl request:

    curl -u username:password <request>

    If KIE Server is configured with Red Hat Single Sign-On, the request must include a bearer token:

    curl -H "Authorization: bearer $TOKEN" <request>
  3. Specify the format of the request and response. The REST API endpoints work with both JSON and XML formats and are set using request headers:

    JSON

    curl -H "accept: application/json" -H "content-type: application/json"

    XML

    curl -H "accept: application/xml" -H "content-type: application/xml"

  4. (Optional) Query the container for a list of deployed decision models:

    [GET] server/containers/{containerId}/dmn

    Example curl request:

    curl -u krisv:krisv -H "accept: application/xml" -X GET "http://localhost:8080/kie-server/services/rest/server/containers/MovieDMNContainer/dmn"

    Sample XML output:

    <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
    <response type="SUCCESS" msg="OK models successfully retrieved from container 'MovieDMNContainer'">
        <dmn-model-info-list>
            <model>
                <model-namespace>http://www.redhat.com/_c7328033-c355-43cd-b616-0aceef80e52a</model-namespace>
                <model-name>dmn-movieticket-ageclassification</model-name>
                <model-id>_99</model-id>
                <decisions>
                    <dmn-decision-info>
                        <decision-id>_3</decision-id>
                        <decision-name>AgeClassification</decision-name>
                    </dmn-decision-info>
                </decisions>
            </model>
        </dmn-model-info-list>
    </response>

    Sample JSON output:

    {
      "type" : "SUCCESS",
      "msg" : "OK models successfully retrieved from container 'MovieDMNContainer'",
      "result" : {
        "dmn-model-info-list" : {
          "models" : [ {
            "model-namespace" : "http://www.redhat.com/_c7328033-c355-43cd-b616-0aceef80e52a",
            "model-name" : "dmn-movieticket-ageclassification",
            "model-id" : "_99",
            "decisions" : [ {
              "decision-id" : "_3",
              "decision-name" : "AgeClassification"
            } ]
          } ]
        }
      }
    }
  5. Execute the model:

    [POST] server/containers/{containerId}/dmn

    Example curl request:

    curl -u krisv:krisv -H "accept: application/json" -H "content-type: application/json" -X POST "http://localhost:8080/kie-server/services/rest/server/containers/MovieDMNContainer/dmn" -d "{ \"model-namespace\" : \"http://www.redhat.com/_c7328033-c355-43cd-b616-0aceef80e52a\", \"model-name\" : \"dmn-movieticket-ageclassification\", \"decision-name\" : [ ], \"decision-id\" : [ ], \"dmn-context\" : {\"Age\" : 66}}"

    Example JSON request:

    {
      "model-namespace" : "http://www.redhat.com/_c7328033-c355-43cd-b616-0aceef80e52a",
      "model-name" : "dmn-movieticket-ageclassification",
      "decision-name" : [ ],
      "decision-id" : [ ],
      "dmn-context" : {"Age" : 66}
    }

    Example XML request (JAXB format):

    <?xml version="1.0" encoding="UTF-8"?>
    <dmn-evaluation-context>
        <model-namespace>http://www.redhat.com/_c7328033-c355-43cd-b616-0aceef80e52a</model-namespace>
        <model-name>dmn-movieticket-ageclassification</model-name>
        <dmn-context xsi:type="jaxbListWrapper" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
            <type>MAP</type>
            <element xsi:type="jaxbStringObjectPair" key="Age">
                <value xsi:type="xs:int" xmlns:xs="http://www.w3.org/2001/XMLSchema">66</value>
            </element>
        </dmn-context>
    </dmn-evaluation-context>
    Note

    Regardless of the request format, the request requires the following elements:

    • Model namespace
    • Model name
    • Context object containing input values

    Example JSON response:

    {
      "type" : "SUCCESS",
      "msg" : "OK from container 'MovieDMNContainer'",
      "result" : {
        "dmn-evaluation-result" : {
          "messages" : [ ],
          "model-namespace" : "http://www.redhat.com/_c7328033-c355-43cd-b616-0aceef80e52a",
          "model-name" : "dmn-movieticket-ageclassification",
          "decision-name" : [ ],
          "dmn-context" : {
            "Age" : 66,
            "AgeClassification" : "Senior"
          },
          "decision-results" : {
            "_3" : {
              "messages" : [ ],
              "decision-id" : "_3",
              "decision-name" : "AgeClassification",
              "result" : "Senior",
              "status" : "SUCCEEDED"
            }
          }
        }
      }
    }

    Example XML (JAXB format) response:

    <?xml version="1.0" encoding="UTF-8" standalone="yes"?>
    <response type="SUCCESS" msg="OK from container 'MovieDMNContainer'">
          <dmn-evaluation-result>
                <model-namespace>http://www.redhat.com/_c7328033-c355-43cd-b616-0aceef80e52a</model-namespace>
                <model-name>dmn-movieticket-ageclassification</model-name>
                <dmn-context xsi:type="jaxbListWrapper" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
                      <type>MAP</type>
                      <element xsi:type="jaxbStringObjectPair" key="Age">
                            <value xsi:type="xs:int" xmlns:xs="http://www.w3.org/2001/XMLSchema">66</value>
                      </element>
                      <element xsi:type="jaxbStringObjectPair" key="AgeClassification">
                            <value xsi:type="xs:string" xmlns:xs="http://www.w3.org/2001/XMLSchema">Senior</value>
                      </element>
                </dmn-context>
                <messages/>
                <decisionResults>
                      <entry>
                            <key>_3</key>
                            <value>
                                  <decision-id>_3</decision-id>
                                  <decision-name>AgeClassification</decision-name>
                                  <result xsi:type="xs:string" xmlns:xs="http://www.w3.org/2001/XMLSchema" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">Senior</result>
                                  <messages/>
                                  <status>SUCCEEDED</status>
                            </value>
                      </entry>
                </decisionResults>
          </dmn-evaluation-result>
    </response>