flowable/flowable-engine · error · FlowableIllegalArgumentException

commentId is null

Error message

commentId is null

What it means

GetCommentCmd's constructor validates its argument eagerly: a null commentId immediately throws FlowableIllegalArgumentException when the command object is instantiated, before any command context runs. The comment id is required to look up a single Comment entity.

Solutions

1. Pass a valid, non-null comment id obtained from taskService.getProcessInstanceComments() / getTaskComments()
2. Add a null/blank check before calling getComment
3. If the comment may not exist, still pass the id and handle a null return from the lookup instead of skipping the call

Example fix

// before
Comment c = taskService.getComment(commentId); // commentId possibly null
// after
if (commentId != null) {
    Comment c = taskService.getComment(commentId);
}

if (commentId == null || commentId.isEmpty()) throw new IllegalArgumentException("commentId required");
Comment c = taskService.getComment(commentId);

boolean hasCommentId(String id) { return id != null && !id.trim().isEmpty(); }

When it happens

Trigger: Calling taskService.getComment(null) or new GetCommentCmd(null) directly; a comment id field that was never set from a preceding API response; refactored code dropping the id parameter.

Common situations: UI passing an unset comment identifier; deserialization of a payload missing the comment id; confusing comment id with task id.

Related errors

• activatedBefore is null
• activity tenant id is null
• after time is null
• after time is null
• app definition tenantId is null

AI-assisted analysis of flowable/flowable-engine@d6d39ce1c6 (2026-09-11). Data as JSON: /api/errors/d5cfaa94d61bb621. Report an issue: GitHub.

Appendix: source

Thrown at modules/flowable-engine/src/main/java/org/flowable/engine/impl/cmd/GetCommentCmd.java:36

import org.flowable.common.engine.api.FlowableIllegalArgumentException;
import org.flowable.common.engine.impl.interceptor.Command;
import org.flowable.common.engine.impl.interceptor.CommandContext;
import org.flowable.engine.impl.util.CommandContextUtil;
import org.flowable.engine.task.Comment;

/**
 * @author Frederik Heremans
 */
public class GetCommentCmd implements Command<Comment>, Serializable {

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

    public GetCommentCmd(String commentId) {
        this.commentId = commentId;

        if (commentId == null) {
            throw new FlowableIllegalArgumentException("commentId is null");
        }
    }

    @Override
    public Comment execute(CommandContext commandContext) {
        return CommandContextUtil.getCommentEntityManager(commandContext).findComment(commentId);
    }
}

View on GitHub (pinned to d6d39ce1c6)