Chapter 16. Execution server

16.1. Assignment rules

Assignment rules are rules executed automatically when a Human Task is created or completed. This mechanism can be used, for example, to assign a Human Task automatically to a particular user of a group or prevent a user from completing a Task if data is missing.

16.1.1. Defining assignment rules

To define assignment rules, do the following:
  1. Create a file that will contain the rule definition on the Business Central classpath (the recommended location is $DEPLOY_DIR/standalone/deployments/business-central.war/WEB-INF/classes/):
    • default-add-task.drl with the rules to be checked when the Human Task is created
    • default-complete-task.drl with the rules to be checked when the Human Task is completed
  2. Define the rules in the file.

Example 16.1. The default-add-task.drl content

package defaultPackage

import org.kie.api.task.model.Task;
import org.kie.api.task.model.User;
import org.kie.api.task.model.Status;
import org.kie.api.task.model.PeopleAssignments;
import org.jbpm.services.task.rule.TaskServiceRequest;
import org.jbpm.services.task.exception.PermissionDeniedException;
import org.jbpm.services.task.impl.model.*;
import java.util.HashMap;
import java.util.List;


global TaskServiceRequest request;

rule "Don't allow Mary to complete task when rejected"
    when
        $task : Task()
        $actualOwner : User( id == 'mary') from $task.getTaskData().getActualOwner()
        $params : HashMap(this["approved"] == false)
    then
        request.setAllowed(false);
        request.setExceptionClass(PermissionDeniedException.class);
        request.addReason("Mary is not allowed to complete task with approved false");
end
If the potential owners of a Human Task will contain the user Mary, the task will be automatically assigned to the user mary.

Example 16.2. The default-complete-task.drl content

package defaultPackage

import org.kie.api.task.model.Task;
import org.kie.api.task.model.User;
import org.kie.api.task.model.Status;
import org.kie.api.task.model.PeopleAssignments;
import org.jbpm.services.task.rule.TaskServiceRequest;
import org.jbpm.services.task.exception.PermissionDeniedException;
import org.jbpm.services.task.impl.model.*;
import java.util.HashMap;
import java.util.List;


global TaskServiceRequest request;

rule "Don't allow Mary to complete task when rejected"
    when
        $task : Task()
        $actualOwner : User( id == 'mary') from $task.getTaskData().getActualOwner()
        $params : HashMap(this["approved"] == false)
    then
        request.setAllowed(false);
        request.setExceptionClass(PermissionDeniedException.class);
        request.addReason("Mary is not allowed to complete task without approval.");
end
If the potential owners of a Human Task will contain the user Mary, the task will be automatically assigned to the user mary.