7.2. 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, 7.48.0.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. 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.

    注記

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