flowable/flowable-engine · error · FlowableIllegalArgumentException

groupId is null

Error message

groupId is null

What it means

CreateMembershipCmd.execute(CommandContext) throws FlowableIllegalArgumentException when its groupId field is null at execution time. Memberships must reference an existing group; a null group id is rejected before touching the entity manager. The constructor validates userId but this check runs when the command executes.

Source

Thrown at modules/flowable-idm-engine/src/main/java/org/flowable/idm/engine/impl/cmd/CreateMembershipCmd.java:43

public class CreateMembershipCmd implements Command<Object>, Serializable {

    private static final long serialVersionUID = 1L;

    String userId;
    String groupId;

    public CreateMembershipCmd(String userId, String groupId) {
        this.userId = userId;
        this.groupId = groupId;
    }

    @Override
    public Object execute(CommandContext commandContext) {
        if (userId == null) {
            throw new FlowableIllegalArgumentException("userId is null");
        }
        if (groupId == null) {
            throw new FlowableIllegalArgumentException("groupId is null");
        }
        CommandContextUtil.getMembershipEntityManager(commandContext).createMembership(userId, groupId);
        return null;
    }
}

View on GitHub (pinned to d6d39ce1c6)

Solutions

  1. Pass a non-null groupId that references an existing group.
  2. Create the group first (identityService.newGroup/saveGroup) if it doesn't exist.
  3. Check group.getId() for null before calling createMembership.

Example fix

// before
identityService.createMembership(userId, group.getId()); // group.getId() null
// after
if (group.getId() == null) {
    identityService.saveGroup(group);
}
identityService.createMembership(userId, group.getId());
Defensive patterns

Strategy: validation

Validate before calling

if (userId != null && groupId != null) { identityService.createMembership(userId, groupId); }

Type guard

boolean canCreateMembership(String userId, String groupId) { return userId != null && groupId != null; }

Try / catch

try { identityService.createMembership(userId, groupId); } catch (FlowableIllegalArgumentException e) { log.error("Membership needs non-null userId and groupId", e); }

Prevention

When it happens

Trigger: Calling identityService.createMembership(userId, null) — the command executes and fails its groupId check.

Common situations: Assignment code resolving the target group from a process variable or LDAP attribute that is missing, yielding null.

Related errors

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/3a3b80ca8d60bc7d. Report an issue: GitHub.