stanfordnlp/CoreNLP · error · RuntimeException

Error loading flags.plainTextDocumentReaderAndWriter

Error message

Error loading flags.plainTextDocumentReaderAndWriter: '%s'

What it means

makePlainTextReaderAndWriter loads the plain-text DocumentReaderAndWriter class by reflection (defaulting to SeqClassifierFlags.DEFAULT_PLAIN_TEXT_READER when flags.plainTextDocumentReaderAndWriter is unset) and wraps any load failure in a RuntimeException naming the flag. Same failure modes as the general readerAndWriter loading.

Solutions

1. Inspect the wrapped cause exception for the real load error
2. Unset the flag to fall back to SeqClassifierFlags.DEFAULT_PLAIN_TEXT_READER, or set it to a valid class like edu.stanford.nlp.objectbank.ObjectBank$LineSplittable... / PlainTextDocumentReaderAndWriter
3. Ensure the class is on the runtime classpath
4. Verify the class implements DocumentReaderAndWriter and has a public no-arg constructor

Example fix

// before
plainTextDocumentReaderAndWriter = edu.stanford.nlp.PlarinTextDocumentReaderAndWriter
// after
plainTextDocumentReaderAndWriter = edu.stanford.nlp.ie.Platinum... -> use correct FQCN, e.g. remove the line to use the default

String cls = flags.plainTextDocumentReaderAndWriter != null ? flags.plainTextDocumentReaderAndWriter : SeqClassifierFlags.DEFAULT_PLAIN_TEXT_READER;
try { Class.forName(cls); } catch (ClassNotFoundException e) { throw new IllegalStateException("bad plainText reader class: " + cls); }

try { rw = classifier.makePlainTextReaderAndWriter(); }
catch (RuntimeException e) { log.error("Bad plainTextDocumentReaderAndWriter: {}", e.getCause(), e); throw e; }

When it happens

Trigger: Calling makePlainTextReaderAndWriter() when flags.plainTextDocumentReaderAndWriter names a nonexistent class, a class without a no-arg constructor, or one that fails during reflective instantiation.

Common situations: Typo in the plainTextDocumentReaderAndWriter property; custom reader class not packaged in the deployed jar; copy-pasted fully-qualified class name with a mistake.

Related errors

• Error loading flags.readerAndWriter
• Unknown class
• Couldn't instantiate CategoryMergingGrammarCompactor.
• Loading: failed with
• Could not load tokenizer factory

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/f8a98b0b9ed8c0ab. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/ie/AbstractSequenceClassifier.java:266

   * Makes a DocumentReaderAndWriter based on
   * flags.plainTextReaderAndWriter.  Useful for reading in
   * untokenized text documents or reading plain text from the command
   * line.  An example of a way to use this would be to return a
   * edu.stanford.nlp.wordseg.Sighan2005DocumentReaderAndWriter for
   * the Chinese Segmenter.
   */
  public static <INN extends CoreMap> DocumentReaderAndWriter<INN> makePlainTextReaderAndWriter(SeqClassifierFlags flags) {
    String readerClassName = flags.plainTextDocumentReaderAndWriter;
    // We set this default here if needed because there may be models
    // which don't have the reader flag set
    if (readerClassName == null) {
      readerClassName = SeqClassifierFlags.DEFAULT_PLAIN_TEXT_READER;
    }
    DocumentReaderAndWriter<INN> readerAndWriter;
    try {
      readerAndWriter = ReflectionLoading.loadByReflection(readerClassName);
    } catch (Exception e) {
      throw new RuntimeException(String.format("Error loading flags.plainTextDocumentReaderAndWriter: '%s'", flags.plainTextDocumentReaderAndWriter), e);
    }
    readerAndWriter.init(flags);
    return readerAndWriter;
  }

  public DocumentReaderAndWriter<IN> makePlainTextReaderAndWriter() {
    return makePlainTextReaderAndWriter(flags);
  }

  /**
   * Returns the background class for the classifier.
   *
   * @return The background class name
   */
  public String backgroundSymbol() {
    return flags.backgroundSymbol;
  }

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