lysine-dev/retrofit · error · NullPointerException

response == null

Error message

response == null

What it means

Result.response(Response) is the public factory for building a success-valued Result, used by the rxjava adapter to wrap a completed HTTP response inside a reactive stream as data. It rejects null because a Result must carry a definite response or a definite error — a null response would make the Result empty and break the response()/error() accessor invariants. It throws NullPointerException ('response == null') behind a ConstantConditions suppression.

Source

Thrown at retrofit-adapters/rxjava/src/main/java/retrofit2/adapter/rxjava/Result.java:32

 * limitations under the License.
 */
package retrofit2.adapter.rxjava;

import java.io.IOException;
import javax.annotation.Nullable;
import retrofit2.Response;

/** The result of executing an HTTP request. */
public final class Result<T> {
  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
  public static <T> Result<T> error(Throwable error) {
    if (error == null) throw new NullPointerException("error == null");
    return new Result<>(null, error);
  }

  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
  public static <T> Result<T> response(Response<T> response) {
    if (response == null) throw new NullPointerException("response == null");
    return new Result<>(response, null);
  }

  private final @Nullable Response<T> response;
  private final @Nullable Throwable error;

  private Result(@Nullable Response<T> response, @Nullable Throwable error) {
    this.response = response;
    this.error = error;
  }

  /**
   * The response received from executing an HTTP request. Only present when {@link #isError()} is
   * false, null otherwise.
   */
  public @Nullable Response<T> response() {
    return response;
  }

View on GitHub (pinned to d0b112dad0)

Solutions

1. Null-check the argument first: `if (resp != null) Result.response(resp) else ...`.
2. If the call should represent a failure, use Result.error(...) instead.
3. Fix the upstream source so it never hands a null Response to the wrapper.

Example fix

// before
Result<User> r = Result.response(cachedResponse);
// after
if (cachedResponse == null) {
  return Result.error(new IllegalStateException("no cached response"));
}
Result<User> r = Result.response(cachedResponse);

Response<User> resp = executeOrCache();
if (resp == null) throw new IllegalStateException("no response available");
Result<User> result = Result.response(resp);

try {
  Result<User> r = Result.response(resp);
} catch (NullPointerException e) {
  // resp was null; treat as an error Result instead
  return Result.error(new IllegalStateException("null response", e));
}

When it happens

Trigger: Calling Result.response(null) — typically in custom operators/transformers or tests that re-wrap a Response reference that resolved to null, or when mapping an empty cache hit. Thrown immediately at the top of Result.response(Response).

Common situations: Writing custom RxJava operators that wrap Response values; mock/test setup; cache layers returning null on miss that are then wrapped unconditionally.

Related errors

• error == null
• response == null
• response == null
• scheduler == null
• Response must be parameterized as Response<Foo> or Response<

AI-assisted analysis of lysine-dev/retrofit@d0b112dad0 (2026-08-13). Data as JSON: /api/errors/7a9213a9a6f9d629. Report an issue: GitHub.