What causes "no null chunk accepted" in eclipse-vertx/vert.x?

Call request.end() with no arguments when there is no final chunk

eclipse-vertx/vert.x · error · NullPointerException

no null chunk accepted

Error message

no null chunk accepted

What it means

end(Buffer) throws a NullPointerException when passed a null buffer, because ending a request with a null final chunk is not supported. The overload end() with no arguments must be used to end the request without a body chunk.

Source

Thrown at vertx-core/src/main/java/io/vertx/core/http/impl/HttpClientRequestImpl.java:497

    }
    promise.complete(resp);
  }

  @Override
  public Future<Void> end(String chunk) {
    return write(BufferInternal.buffer(chunk), true);
  }

  @Override
  public Future<Void> end(String chunk, String enc) {
    Objects.requireNonNull(enc, "no null encoding accepted");
    return write(BufferInternal.buffer(chunk, enc), true);
  }

  @Override
  public Future<Void> end(Buffer chunk) {
    if (chunk == null) {
      throw new NullPointerException("no null chunk accepted");
    }
    return write(chunk, true);
  }

  @Override
  public Future<Void> end() {
    return write(null, true);
  }

  @Override
  public Future<Void> write(Buffer chunk) {
    if (chunk == null) {
      throw new NullPointerException("no null chunk accepted");
    }
    return write(chunk, false);
  }

  @Override

View on GitHub (pinned to fb308bd8c3)

Solutions

Call request.end() with no arguments when there is no final chunk
Guard for null before calling end and fall back to the no-arg end()
Ensure the buffer-producing code never yields null (use Buffer.buffer() for empty)

Example fix

// before
request.end(maybeNullBuffer);
// after
if (maybeNullBuffer != null) {
  request.end(maybeNullBuffer);
} else {
  request.end();
}

Defensive patterns

Strategy: type-guard

Validate before calling

if (chunk == null) { request.end(); return; }

Type guard

void safeEnd(HttpClientRequest req, Buffer chunk) {
  if (chunk != null) req.end(chunk); else req.end();
}

Try / catch

try {
  request.end(chunk);
} catch (NullPointerException e) {
  request.end();
}

Prevention

Use end() (no-arg) when there is no final body chunk
Use Buffer.buffer() for an empty body instead of null
Add null checks where bodies come from nullable sources

When it happens

Trigger: Calling request.end(null) directly, or passing a variable that is null (e.g. an absent request body) to end(Buffer).

Common situations: Code that reads a body into a Buffer that may be null on some paths then calls end(buffer); generic wrappers that forward a nullable payload to end().

Related errors

AI-assisted analysis of eclipse-vertx/vert.x@fb308bd8c3 (2026-09-06). Data as JSON: /api/errors/0a6102d2d9d777cf. Report an issue: GitHub.