flowable/flowable-engine · error · ActivitiIllegalArgumentException

identityId is null

Error message

identityId is null

What it means

AddIdentityLinkCmd.validateParams rejects a null identityId unless the link is a group link or an ASSIGNEE/OWNER link (where the id may legitimately be null to unset). Flowable throws ActivitiIllegalArgumentException because the link would reference neither a user nor a group.

Solutions

1. Pass a non-null userId/groupId, or use type IdentityLinkType.ASSIGNEE or OWNER with null to clear
2. Use IDENTITY_GROUP (2) as identityIdType if you intended a group link with null user id
3. Validate the resolved user id before invoking the command

Example fix

// before
taskService.addUserIdentityLink(taskId, userId, IdentityLinkType.CANDIDATE); // userId null
// after
if (userId == null) {
    taskService.setAssignee(taskId, null); // to clear, use assignee
} else {
    taskService.addUserIdentityLink(taskId, userId, IdentityLinkType.CANDIDATE);
}

boolean idMayBeNull = IdentityLinkType.ASSIGNEE.equals(type) || IdentityLinkType.OWNER.equals(type);
if (identityId == null && !idMayBeNull) {
    throw new IllegalArgumentException("identityId required for type " + type);
}

try {
    taskService.addUserIdentityLink(taskId, userId, type);
} catch (ActivitiIllegalArgumentException e) {
    if (e.getMessage().equals("identityId is null")) {
        taskService.setAssignee(taskId, null); // clearing via assignee
    } else { throw e; }
}

When it happens

Trigger: Calling taskService.addUserIdentityLink(taskId, null, type) with a non-assignee/owner type; AddIdentityLinkCmd constructed with identityId == null and identityIdType == IDENTITY_USER with a type other than ASSIGNEE/OWNER.

Common situations: Swapping the userId and type parameters by mistake; the user id lookup returned null upstream and was passed along; intending to clear an assignee but using a candidate/participant type instead.

Related errors

• taskId is null
• type is required when adding a new task identity link
• appDefinitionId is null
• identityId is null
• processDefinitionId is null

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/12afb91857c7bc4c. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable5-engine/src/main/java/org/activiti/engine/impl/cmd/AddIdentityLinkCmd.java:57

        this.taskId = taskId;
        this.identityId = identityId;
        this.identityIdType = identityIdType;
        this.identityType = identityType;
    }

    protected void validateParams(String taskId, String identityId, int identityIdType, String identityType) {
        if (taskId == null) {
            throw new ActivitiIllegalArgumentException("taskId is null");
        }

        if (identityType == null) {
            throw new ActivitiIllegalArgumentException("type is required when adding a new task identity link");
        }

        if (identityId == null && (identityIdType == IDENTITY_GROUP ||
                (!IdentityLinkType.ASSIGNEE.equals(identityType) && !IdentityLinkType.OWNER.equals(identityType)))) {

            throw new ActivitiIllegalArgumentException("identityId is null");
        }

        if (identityIdType != IDENTITY_USER && identityIdType != IDENTITY_GROUP) {
            throw new ActivitiIllegalArgumentException("identityIdType allowed values are 1 and 2");
        }
    }

    @Override
    protected Void execute(CommandContext commandContext, TaskEntity task) {

        boolean assignedToNoOne = false;
        if (IdentityLinkType.ASSIGNEE.equals(identityType)) {
            task.setAssignee(identityId, true, true);
            assignedToNoOne = identityId == null;
        } else if (IdentityLinkType.OWNER.equals(identityType)) {
            task.setOwner(identityId, true);
        } else if (IDENTITY_USER == identityIdType) {
            task.addUserIdentityLink(identityId, identityType);

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