flowable/flowable-engine · error · FlowableIllegalArgumentException

taskIds is null

Error message

taskIds is null

What it means

GetTasksLocalVariablesCmd.execute() bulk-fetches local variable instances for a set of task ids. It rejects a null taskIds collection with FlowableIllegalArgumentException('taskIds is null') because the query cannot be built without an id set.

Source

Thrown at modules/flowable-cmmn-engine/src/main/java/org/flowable/cmmn/engine/impl/cmd/GetTasksLocalVariablesCmd.java:45

import org.flowable.variable.service.impl.persistence.entity.VariableInstanceEntity;

/**
 * @author Tijs Rademakers
 */
public class GetTasksLocalVariablesCmd implements Command<List<VariableInstance>>, Serializable {

    private static final long serialVersionUID = 1L;
    
    protected Set<String> taskIds;

    public GetTasksLocalVariablesCmd(Set<String> taskIds) {
        this.taskIds = taskIds;
    }

    @Override
    public List<VariableInstance> execute(CommandContext commandContext) {
        if (taskIds == null) {
            throw new FlowableIllegalArgumentException("taskIds is null");
        }
        if (taskIds.isEmpty()) {
            throw new FlowableIllegalArgumentException("Set of taskIds is empty");
        }

        CmmnEngineConfiguration cmmnEngineConfiguration = CommandContextUtil.getCmmnEngineConfiguration(commandContext);
        List<VariableInstanceEntity> entities = cmmnEngineConfiguration.getVariableServiceConfiguration()
                .getVariableService().createInternalVariableInstanceQuery().taskIds(taskIds).list();
        List<VariableInstance> instances = new ArrayList<>(entities.size());
        for (VariableInstanceEntity entity : entities) {
            entity.getValue();
            instances.add(entity);
        }

        return instances;
    }

}

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Initialize taskIds to an empty Set/List instead of null before calling the bulk API.
2. Null-check the collection parameter at the call site.
3. Fix the upstream producer of the id collection to return an empty collection rather than null.

Example fix

// before
List<VariableInstance> vars = cmmnTaskService.getVariableInstancesLocalByTaskIds(taskIds);
// after
Set<String> ids = (taskIds != null) ? taskIds : Collections.emptySet();
if (!ids.isEmpty()) {
    List<VariableInstance> vars = cmmnTaskService.getVariableInstancesLocalByTaskIds(ids);
}

if (taskIds == null) { throw new IllegalArgumentException("taskIds collection must be initialized"); }

boolean hasTaskIds(Collection<String> taskIds) { return taskIds != null; }

try { return taskService.getVariableInstancesLocalByTaskIds(taskIds); } catch (FlowableIllegalArgumentException e) { return Collections.emptyList(); }

When it happens

Trigger: Calling cmmnTaskService.getVariableInstancesLocalByTaskIds(null) (or the corresponding bulk task-variables API); executing a directly constructed GetTasksLocalVariablesCmd(null).

Common situations: Caller built the id set conditionally and never initialized it; upstream query returned null instead of an empty list; integration glue that forwards a nullable collection parameter.

Related errors

• Case instance id is null
• Plan item instance id is null
• taskId is null
• caseInstanceId is required
• taskId is required

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/4320ab3a2ca68b2e. Report an issue: GitHub.