flowable/flowable-engine · error · FlowableIllegalArgumentException

taskId is required

Error message

taskId is required

What it means

The GetHistoricEntityLinkChildrenForTaskCmd constructor requires a taskId and throws FlowableIllegalArgumentException when it is null. Historic entity links for a task (its children such as sub-tasks or related process instances) cannot be queried without the task id.

Solutions

1. Resolve and verify the task id via taskService.createTaskQuery().taskId(id).singleResult() (or historyService) before querying entity links.
2. Guard against null ids at the call site and return an empty result instead.
3. Ensure you are passing a task id, not a process instance or execution id.

Example fix

// before
historyService.findHistoricEntityLinkChildrenForTask(taskId);
// after
if (taskId == null) {
    return Collections.emptyList();
}
historyService.findHistoricEntityLinkChildrenForTask(taskId);

if (taskId == null) { return Collections.emptyList(); }

try {
    return historyService.findHistoricEntityLinkChildrenForTask(taskId);
} catch (FlowableIllegalArgumentException e) {
    return Collections.emptyList();
}

When it happens

Trigger: new GetHistoricEntityLinkChildrenForTaskCmd(null) — usually when a task lookup (runtime or historic) returned null and its id was passed on without a check.

Common situations: Chaining calls after taskService.createTaskQuery().singleResult() that returned no row; tasks completed long ago and removed from history; using a processInstanceId where a taskId is expected.

Related errors

• taskId is required
• processInstanceId is required
• processInstanceId is required
• processInstanceId is required
• A delegated cannot be completed, but should be resolved…

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/8f6b6686a88dc495. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-engine/src/main/java/org/flowable/engine/impl/cmd/GetHistoricEntityLinkChildrenForTaskCmd.java:37

import org.flowable.common.engine.api.scope.ScopeTypes;
import org.flowable.common.engine.impl.interceptor.Command;
import org.flowable.common.engine.impl.interceptor.CommandContext;
import org.flowable.engine.impl.cfg.ProcessEngineConfigurationImpl;
import org.flowable.engine.impl.util.CommandContextUtil;
import org.flowable.entitylink.api.EntityLinkType;
import org.flowable.entitylink.api.history.HistoricEntityLink;

/**
 * @author Javier Casal
 */
public class GetHistoricEntityLinkChildrenForTaskCmd implements Command<List<HistoricEntityLink>>, Serializable {

    private static final long serialVersionUID = 1L;
    protected String taskId;

    public GetHistoricEntityLinkChildrenForTaskCmd(String taskId) {
        if (taskId == null) {
            throw new FlowableIllegalArgumentException("taskId is required");
        }
        this.taskId = taskId;
    }

    @Override
    public List<HistoricEntityLink> execute(CommandContext commandContext) {
        ProcessEngineConfigurationImpl processEngineConfiguration = CommandContextUtil.getProcessEngineConfiguration(commandContext);
        return processEngineConfiguration.getEntityLinkServiceConfiguration().getHistoricEntityLinkService()
                .findHistoricEntityLinksByScopeIdAndScopeType(taskId, ScopeTypes.TASK, EntityLinkType.CHILD);
    }

}

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