stanfordnlp/CoreNLP · error · RuntimeIOException

RuntimeIOException

Error message

RuntimeIOException

What it means

SingletonPredictor.saveToSerialized wraps any IOException that occurs while opening or writing the ObjectOutputStream for the model file in a RuntimeIOException and rethrows it. This converts a checked I/O failure during model persistence into an unchecked exception.

Solutions

1. Ensure the target directory exists and is writable before calling saveToSerialized
2. Use a plain writable file path rather than an invalid IOUtils resource string
3. Check disk space/quota if the failure occurs mid-write
4. Catch RuntimeIOException to translate it into a clear save-failure message

Example fix

// before
predictor.saveToSerialized("out/singleton.ser");
// after
new File("out").mkdirs();
predictor.saveToSerialized("out/singleton.ser");

File out = new File(filename);
File parent = out.getAbsoluteFile().getParentFile();
if (parent != null && !parent.isDirectory() && !parent.mkdirs()) throw new IOException("Cannot create dir " + parent);
if (out.exists() && !out.canWrite()) throw new IOException("Not writable: " + out);

try {
  predictor.saveToSerialized(filename);
} catch (RuntimeIOException e) {
  log.severe("Saving singleton predictor failed: " + e.getCause());
  throw e;
}

When it happens

Trigger: Calling SingletonPredictor.saveToSerialized(filename) when the output path cannot be opened (bad path, unwritable directory, invalid URL-style resource specification via IOUtils.writeStreamFromString) or the write itself fails (disk full, stream closed).

Common situations: Saving trained predictor to a nonexistent directory; lacking write permissions; typos in the output filename/resource string; disk quota exceeded during training pipelines.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

• RuntimeIOException
• RuntimeIOException wrapping IOException
• Error creating data exporter
• RuntimeException with no message (model write failure)
• RuntimeIOException wrapping IOException

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/5cf96f442da8ea64. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/dcoref/SingletonPredictor.java:150

    LogisticClassifier<String, String> classifier = lcf.trainClassifier(pDataset);

    return classifier;
  }

  /**
   * Saves the singleton predictor model to the given filename.
   * If there is an error, a RuntimeIOException is thrown.
   */
  private static void saveToSerialized(LogisticClassifier<String, String> predictor,
                                       String filename) {
    try {
      log.info("Writing singleton predictor in serialized format to file " + filename + ' ');
      ObjectOutputStream out = IOUtils.writeStreamFromString(filename);
      out.writeObject(predictor);
      out.close();
      log.info("done.");
    } catch (IOException ioe) {
      throw new RuntimeIOException(ioe);
    }
  }

  public static void main(String[] args) throws Exception {
    Properties props;
    if (args.length > 0) {
      props = StringUtils.argsToProperties(args);
    } else {
      props = new Properties();
    }
    if ( ! props.containsKey("dcoref.conll2011")) {
      log.info("-dcoref.conll2011 [input_CoNLL_corpus]: was not specified");
      return;
    }
    if ( ! props.containsKey("singleton.predictor.output")) {
      log.info("-singleton.predictor.output [output_model_file]: was not specified");
      return;
    }

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