flowable/flowable-engine · error · FlowableIllegalArgumentException

taskId is null

Error message

taskId is null

What it means

FlowableIllegalArgumentException thrown by ActivateTaskCmd.execute when the taskId constructor argument is null. The command cannot look up a task without an id, so it fails fast before touching the database.

Source

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

import org.flowable.task.service.HistoricTaskService;
import org.flowable.task.service.impl.persistence.entity.TaskEntity;

public class ActivateTaskCmd implements Command<Void> {

    protected String taskId;
    protected String userId;

    public ActivateTaskCmd(String taskId, String userId) {
        this.taskId = taskId;
        this.userId = userId;
    }

    @Override
    public Void execute(CommandContext commandContext) {
        ProcessEngineConfigurationImpl processEngineConfiguration = CommandContextUtil.getProcessEngineConfiguration(commandContext);
        
        if (taskId == null) {
            throw new FlowableIllegalArgumentException("taskId is null");
        }

        TaskEntity task = processEngineConfiguration.getTaskServiceConfiguration().getTaskService().getTask(taskId);

        if (task == null) {
            throw new FlowableObjectNotFoundException("Cannot find task with id " + taskId, Task.class);
        }

        if (task.isDeleted()) {
            throw new FlowableException(task + " is already deleted");
        }

        if (!task.isSuspended()) {
            throw new FlowableException(task + " is not suspended, so can't be activated");
        }
        
        Clock clock = processEngineConfiguration.getClock();
        Date updateTime = clock.getCurrentTime();

View on GitHub (pinned to d6d39ce1c6)

Solutions

1. Ensure taskId is non-null before calling taskService.activateTask(taskId).
2. Check the source of the id: if it comes from Task.getId(), verify the task was actually created/queried successfully.
3. Guard the call site with an explicit null check or Objects.requireNonNull to fail earlier with a clearer message.
4. Fix upstream logic that returns null ids (e.g. singleResult() on an empty query).

Example fix

// before
taskService.activateTask(taskId); // taskId may be null
// after
if (taskId == null) {
    throw new IllegalArgumentException("taskId must be provided");
}
taskService.activateTask(taskId);

java.util.Objects.requireNonNull(taskId, "taskId must not be null");
taskService.activateTask(taskId);

When it happens

Trigger: Calling taskService.activateTask(null) or constructing new ActivateTaskCmd(null); passing a variable that was never populated to taskService.activateTask(...).

Common situations: A null taskId returned from a lookup chain (e.g. taskQuery found nothing and the id variable defaulted to null); programmatic suspension helpers fed null after an earlier failed query.

Related errors

• taskId is null
• taskId is null
• variableName is null
• Cannot find task with id {taskId}
• taskId is null

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/5dc2cd69b83107ac. Report an issue: GitHub.