What causes "Parser context is not supported" in apache/iceberg?

Pass null for parserContext and use the plain get overload

apache/iceberg · error · UnsupportedOperationException

Parser context is not supported

Error message

Parser context is not supported

What it means

The RESTClient default get(..., parserContext) overload does not support a ParserContext argument; passing a non-null context throws UnsupportedOperationException and the call falls back to the plain get. Parser contexts are only honored by clients/overloads that explicitly accept them.

Solutions

Pass null for parserContext and use the plain get overload
Ensure a concrete client implementation supports parser contexts before using this overload
Remove the parserContext argument if response parsing needs no context

Example fix

// before
client.get(path, params, type, headers, handler, parserContext); // non-null context
// after
client.get(path, params, type, headers, handler);

Defensive patterns

Strategy: validation

Validate before calling

if (parserContext != null) {
  throw new IllegalArgumentException("Default RESTClient.get does not support ParserContext");
}

Try / catch

try {
  return client.get(path, params, type, headers, handler, parserContext);
} catch (UnsupportedOperationException e) {
  return client.get(path, params, type, headers, handler);
}

Prevention

Pass null for parserContext on the default interface
Only use the extended overload with clients that implement it
Keep call sites aligned with the concrete client's capabilities

When it happens

Trigger: Calling the extended get(path, queryParams, responseType, headers, errorHandler, parserContext) with a non-null parserContext on the default RESTClient; passing a context 'just in case' when it is unnecessary.

Common situations: Copy-pasting code written against a richer HTTP client into one using the RESTClient interface defaults; new API surface used before the concrete client implements it.

Understand the failure class

Background: UnsupportedOperationException and "is not supported" errors: when a library deliberately refuses a call — this error's family across 30 libraries.

Related errors

AI-assisted analysis of apache/iceberg@86d9c8fc54 (2026-09-12). Data as JSON: /api/errors/e04720340e9d998e. Report an issue: GitHub.

Appendix: source

Thrown at core/src/main/java/org/apache/iceberg/rest/RESTClient.java:108

  default <T extends RESTResponse> T get(
      String path,
      Map<String, String> queryParams,
      Class<T> responseType,
      Supplier<Map<String, String>> headers,
      Consumer<ErrorResponse> errorHandler) {
    return get(path, queryParams, responseType, headers.get(), errorHandler);
  }

  default <T extends RESTResponse> T get(
      String path,
      Map<String, String> queryParams,
      Class<T> responseType,
      Map<String, String> headers,
      Consumer<ErrorResponse> errorHandler,
      ParserContext parserContext) {
    if (parserContext != null) {
      throw new UnsupportedOperationException("Parser context is not supported");
    }
    return get(path, queryParams, responseType, headers, errorHandler);
  }

  default <T extends RESTResponse> T get(
      String path,
      Map<String, String> queryParams,
      Class<T> responseType,
      Supplier<Map<String, String>> headers,
      Consumer<ErrorResponse> errorHandler,
      Consumer<Map<String, String>> responseHeaders) {
    return get(path, queryParams, responseType, headers.get(), errorHandler, responseHeaders);
  }

  default <T extends RESTResponse> T get(
      String path,
      Map<String, String> queryParams,
      Class<T> responseType,

View on GitHub (pinned to 86d9c8fc54)