square/retrofit · error · NullPointerException

context == null

Error message

context == null

What it means

NullPointerException thrown by JaxbConverterFactory.create(JAXBContext) when the supplied context is null (line 45). Note this only applies to the explicit-argument factory: the no-arg create() intentionally passes null to the private constructor (line 39) to mean 'create a fresh JAXBContext per type' (see contextForType at line 79). The guard therefore only rejects an explicit null passed by the caller, failing fast rather than NPE-ing later.

Source

Thrown at retrofit-converters/jaxb/src/main/java/retrofit2/converter/jaxb/JaxbConverterFactory.java:45

import retrofit2.Converter;
import retrofit2.Retrofit;

/**
 * A {@linkplain Converter.Factory converter} which uses JAXB for XML. All validation events are
 * ignored.
 */
public final class JaxbConverterFactory extends Converter.Factory {
  static final MediaType XML = MediaType.get("application/xml; charset=utf-8");

  /** Create an instance using a default {@link JAXBContext} instance for conversion. */
  public static JaxbConverterFactory create() {
    return new JaxbConverterFactory(null);
  }

  /** Create an instance using {@code context} for conversion. */
  @SuppressWarnings("ConstantConditions") // Guarding public API nullability.
  public static JaxbConverterFactory create(JAXBContext context) {
    if (context == null) throw new NullPointerException("context == null");
    return new JaxbConverterFactory(context);
  }

  /** If null, a new JAXB context will be created for each type to be converted. */
  private final @Nullable JAXBContext context;

  private JaxbConverterFactory(@Nullable JAXBContext context) {
    this.context = context;
  }

  @Override
  public @Nullable Converter<?, RequestBody> requestBodyConverter(
      Type type,
      Annotation[] parameterAnnotations,
      Annotation[] methodAnnotations,
      Retrofit retrofit) {
    if (type instanceof Class && ((Class<?>) type).isAnnotationPresent(XmlRootElement.class)) {
      return new JaxbRequestConverter<>(contextForType((Class<?>) type), (Class<?>) type);

View on GitHub (pinned to d0b112dad0)

Solutions

1. If you want default per-type context creation, call the no-arg `JaxbConverterFactory.create()` instead of passing null.
2. If you need a shared context, build one explicitly: `JAXBContext.newInstance(MyType.class)` and ensure it is non-null before passing (it throws JAXBException on failure, so catch and handle, do not null-out).
3. On JDK 9+, add `--add-modules java.xml.bind` (or ship the jakarta.xml.bind API/impl) so JAXBContext.newInstance succeeds rather than returning null/throwing.

Example fix

// before
JAXBContext ctx = buildContextOrNull(); // null when construction failed
Retrofit retrofit = new Retrofit.Builder()
    .addConverterFactory(JaxbConverterFactory.create(ctx))
    .build();

// after — use the no-arg factory for per-type lazy contexts
Retrofit retrofit = new Retrofit.Builder()
    .addConverterFactory(JaxbConverterFactory.create())
    .build();

// Distinguish the legitimate no-arg factory (lazy per-type context) from an
// explicit shared context, and never pass an explicit null.
JAXBContext ctx = buildSharedContext(); // returns non-null or throws JAXBException
JaxbConverterFactory factory = (ctx != null)
    ? JaxbConverterFactory.create(ctx)
    : JaxbConverterFactory.create(); // default, per-type lazy context

try {
  factory = (context != null)
      ? JaxbConverterFactory.create(context)
      : JaxbConverterFactory.create();
} catch (NullPointerException e) {
  throw new IllegalStateException(
      "JAXBContext was null; use create() for the default per-type context", e);
}

When it happens

Trigger: Calling `JaxbConverterFactory.create(context)` where `context` is null. Distinguish from the legitimate `JaxbConverterFactory.create()` no-arg call, which is fine and produces the per-type lazy behavior.

Common situations: DI-provided JAXBContext bean missing or failed to build (e.g. JAXBException during context creation swallowed); a helper returning null when the context could not be constructed; passing null by mistake intending the default; JDK 9+ module access issues causing JAXBContext.newInstance to fail upstream and yielding null in calling code.

Related errors

• gson == null
• mapper == null
• ListenableFuture return type must be parameterized as Listen
• Response must be parameterized as Response<Foo> or Response<
• CompletableFuture return type must be parameterized as Compl

AI-assisted analysis of square/retrofit@d0b112dad0 (2026-08-04). Data as JSON: /data/errors/f8f512eb3e8c592c.json. Report an issue: GitHub.