Process with Decisions Integration through Business Rule Task
Description
This is an example project that shows the usage of decisions within processes. Decisions can be expressed in different domains or assets, such as DMN and DRL. The focus here is to show how to integrate decisions in an embedded way using Business Rule Task where they must be deployed together with the process, in the same application. All assets(bpmn, dmn, drl) must be under the resources.
This example covers the following items:
- DMN to define a decision service
- DRL to define rules decision service
- How to integrate the process with decisions using Business Rule Task
The Traffic Process example:
It is based on the traffic violation evaluation process, where it is required to fetch Driver information, and based on this, it is first performed the license validation to check if the driver has a valid license (using a RuleUnit in a DRL) after the license validation it is then executed the violation evaluation defined as a DMN decision and following, it is checked in the process if the output contains information whether the driver was suspended or not, completing the process.
Process using Business Rule Task
This is a declarative approach, it does not require to have any extra implementation, the interaction with decisions is executed out-of-the-box by the engine. The information needed to execute the decision evaluation should be set in the Data Assignments in the Business Rule Task.
The BPMN file where this process is declared is traffic-rules-dmn.bpmn.
These are the properties defined for the process, the most important one in this section to pay attention is the ID because it is used in the REST endpoint generation referring to the path to interact with this process.
The variables used in the process itself, but the focus in this example are the classes that are used to define the POJOs to interact the process with decisions, that are the Violation, Driver, Fine.
Mapping data from Process to/from DMN
It is important to mention DMN for instance can define the Data Type in its structure, but we can align all attributes names in a Java class that is used as process variables, in case the attribute names contain spaces or are not following java conventions we can use Jackson annotations to make the process variable POJOs aligned with DMN data types, for instance in the Violation class, where it is mapped the speedLimit attribute as Speed Limit using @JsonProperty annotation, in this case, this attribute from the process variable with Violation can be seamlessly integrated Violation Data Type defined in DMN.
Violation Data Type in DMN
Fetch for driver information, in this implementation it is just mocking a result, that simply fill with an expired license date in case the driverId is an odd number and with a valid date in case of an even number. In a real use case, it could be performing an external call to a service or a database to get this information.
The service task implementation is done in the DriverService class.
In the data assignment the input is the driverId and output is the driver variable, filled with all driver information.
Represents the task to do the call to the DRL service.
The properties to be set are mainly the Rule Languagethat should be set as DRL and the Rule Flow Group with unit: + [the FQCN of the Rule Unit Data class], in this case org.kie.kogito.traffic.LicenseValidationService.
The input and output mapping for this task is just the driver variable that is filled with license validation information.
Similar to the License Validation Task, but it represents the task to do the call to the DMN service.
The properties to be set are mainly the Rule Languagethat should be set as DMN and the Namespace and DMN Model Name must be set with the values defined in in the DMN, in this case TrafficViolation.dmn.
The input for this task is the Driver and Violation variables, and the outputs are the Suspended and Fine.
Just an example task where it could be performed any action based on the condition in which the driver is suspended. In the current implementation, it is just logging the information in the console.
Just an example task where it could be performed any action based on the condition in which the driver is not suspended. In the current implementation, it is just logging the information in the console.
Decisions
License Validation - Rule Unit
This decision consistis in rules which are evaluated to check if a driver's license is expired or not according to the expiration date and thus populating the result in the information in the driver variable.
The DRL file where this Rule Unit is declared is LicenseValidationService.drl and the the Java class that contains the Rule Unit Data is LicenseValidationService.
Traffic Violation - DMN
This decision consists in a DMN that basically checks if a driver is suspended or not according to the violation and current driver points in its license.
The DMN file where this decision is declared is TrafficViolation.dmn
Build and run
Prerequisites
You will need:
- Java 17+ installed
- Environment variable JAVA_HOME set accordingly
- Maven 3.9.6+ installed
When using native image compilation, you will also need:
- GraalVM 19.3+ installed
- Environment variable GRAALVM_HOME set accordingly
- GraalVM native image needs as well native-image extension: https://www.graalvm.org/reference-manual/native-image/
- Note that GraalVM native image compilation typically requires other packages (glibc-devel, zlib-devel and gcc) to be installed too, please refer to GraalVM installation documentation for more details.
Compile and Run in Local Dev Mode
mvn clean compile quarkus:dev
NOTE: With dev mode of Quarkus you can take advantage of hot reload for business assets like processes, rules, decision tables and java code. No need to redeploy or restart your running application.
Package and Run in JVM mode
mvn clean package java -jar target/quarkus-app/quarkus-run.jar
or on windows
mvn clean package java -jar target\quarkus-app\quarkus-run.jar
Package and Run using Local Native Image
Note that the following configuration property needs to be added to application.properties in order to enable automatic registration of META-INF/services entries required by the workflow engine:
quarkus.native.auto-service-loader-registration=true
Note that this requires GRAALVM_HOME to point to a valid GraalVM installation
mvn clean package -Pnative
To run the generated native executable, generated in target/, execute
./target/process-decision-quarkus-runner
OpenAPI (Swagger) documentation
You can take a look at the OpenAPI definition - automatically generated and included in this service - to determine all available operations exposed by this service. For easy readability you can visualize the OpenAPI definition file using a UI tool like for example available Swagger UI.
In addition, various clients to interact with this service can be easily generated using this OpenAPI definition.
When running in either Quarkus Development or Native mode, we also leverage the Quarkus OpenAPI extension that exposes Swagger UI that you can use to look at available REST endpoints and send test requests.
Example Usage
Once the service is up and running we can invoke the REST endpoints and examine the logic.
Submit a request
To make use of this application it is as simple as putting a sending request to http://localhost:8080/traffic with appropriate contents. See the following cases:
Valid License and Suspended Driver
Given data:
{ "driverId": "12345", "violation":{ "Type":"speed", "Speed Limit": 100, "Actual Speed":140 } }
Submit the JSON object from above:
curl -X POST -H 'Content-Type:application/json' -H 'Accept:application/json' -d '{"driverId": "12345","violation":{"Type":"speed","Speed Limit": 100,"Actual Speed":140}}' http://localhost:8080/traffic
After the Curl command you should see a similar console log
{ "id": "06ecbbb0-4972-431d-9b37-355d83bb1092", "driverId": "12345", "driver": { "licenseExpiration": "2021-08-13T17:59:08.589+00:00", "validLicense": true, "Name": "Arthur", "State": "SP", "City": "Campinas", "Points": 13, "Age": 30 }, "fine": { "Amount": 1000.0, "Points": 7 }, "violation": { "Code": null, "Date": null, "Type": "speed", "Speed Limit": 100, "Actual Speed": 140 }, "suspended": "Yes" }
You can play with different attributes, if the driverId is an odd number in this case 12345 the license will be evaluated as valid because the DriverService generates a valid expiration date and DMN is evaluated, you can change the actual speed to 140 or 100 to simulate the driver suspension on the DMN evaluation.
If the driverId is an even number like 1234 the license will be evaluated as expired and the DMN will not be evaluated, so Suspended response attribute should be null.
Expired Valid License
Given data:
{ "driverId": "1234", "violation":{ "Type":"speed", "Speed Limit": 100, "Actual Speed":110 } }
Submit the JSON object from above:
curl -X POST -H 'Content-Type:application/json' -H 'Accept:application/json' -d '{"driverId": "1234","violation":{"Type":"speed","Speed Limit": 100,"Actual Speed":110}}' http://localhost:8080/traffic
After the Curl command, you should see a similar console log
{ "id": "887d8f39-93ec-43cc-96e5-df8e9bb199f8", "driverId": "1234", "driver": { "licenseExpiration": "2021-08-12T17:59:37.703+00:00", "validLicense": false, "Name": "Arthur", "State": "SP", "City": "Campinas", "Points": 13, "Age": 30 }, "fine": null, "violation": { "Code": null, "Date": null, "Type": "speed", "Speed Limit": 100, "Actual Speed": 110 }, "suspended": null }
In this case the driver license is expired when the DRL is evaluated because the DriverService generated an expired date for the driver's license thus DMN is not evaluated, so the validLicense is false, suspended and fine are null.