stanfordnlp/CoreNLP · error · java.lang.IllegalArgumentException

Provided mapping file is in wrong format: " + line

Error message

Provided mapping file is in wrong format: " + line

What it means

RegexNERSequenceClassifier.readEntries parses each non-blank mapping line as TAB-separated fields: regex (1-3 columns accepted: 2 to 4 total fields — regex, type, optional overwritable types, optional priority). A line whose field count is outside 2-4 triggers this IllegalArgumentException, identifying the offending line.

Solutions

  1. Ensure each line has exactly 2-4 TAB-separated fields: regex, type, optional overwrite list, optional priority.
  2. Replace space separators with real tab characters (awk -F'\t' 'NF<2||NF>4' file to find bad lines).
  3. Comment out or remove non-conforming lines (comments must start with #).
  4. Check for double tabs or trailing tab characters creating empty extra fields.

Example fix

// before (spaces, no type column)
Apple Inc is_a_company
// after (tabs, regex + type)
Apple\s+Inc\tORGANIZATION
Defensive patterns

Strategy: validation

Validate before calling

// lint mapping lines before loading
try (Stream<String> lines = Files.lines(Paths.get(mappingPath))) {
  List<String> bad = lines.filter(l -> !l.trim().isEmpty() && !l.startsWith("#"))
      .filter(l -> { String[] p = l.split("\t", -1); return p.length < 2 || p.length > 4; })
      .collect(Collectors.toList());
  if (!bad.isEmpty()) throw new IllegalStateException("Bad mapping lines: " + bad);
}

Try / catch

try {
  classifier = new RegexNERSequenceClassifier(props, mapping, true, false);
} catch (IllegalArgumentException e) {
  if (e.getMessage().startsWith("Provided mapping file is in wrong format")) {
    log.severe("Fix mapping line: " + e.getMessage());
  }
  throw e;
}

Prevention

When it happens

Trigger: Loading a regexner mapping file containing lines with fewer than 2 or more than 4 tab-separated fields — e.g. lines with no type column, comment/header lines not starting with '#', spaces used instead of tabs, or stray tabs in descriptions.

Common situations: Hand-edited or CSV-exported rule files using spaces instead of tabs, Excel/Sheets exports introducing extra columns, Windows line endings with embedded tabs, or documentation example lines left in the file.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Related errors

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/5b125111a2840ef7. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/ie/regexp/RegexNERSequenceClassifier.java:284

   *  Creates a combined list of Entries using the provided mapping file, and sorts them by
   *  first by priority, then the number of tokens in the regex.
   *
   *  @param mapping The Reader containing RegexNER mappings. It's lines are counted from 1
   *  @return a sorted list of Entries
   */
  private static List<Entry> readEntries(BufferedReader mapping, boolean ignoreCase) throws IOException {
    List<Entry> entries = new ArrayList<>();

    int lineCount = 0;
    for (String line; (line = mapping.readLine()) != null; ) {
      lineCount ++;
      // skip blank lines
      if (line.trim().equals(""))
        continue;

      String[] split = line.split("\t");
      if (split.length < 2 || split.length > 4)
        throw new IllegalArgumentException("Provided mapping file is in wrong format: " + line);

      String[] regexes = split[0].trim().split("\\s+");
      String type = split[1].trim();
      Set<String> overwritableTypes = Generics.newHashSet();
      double priority = 0.0;
      List<Pattern> tokens = new ArrayList<>();

      if (split.length >= 3) {
        overwritableTypes.addAll(Arrays.asList(split[2].trim().split(",")));
      }
      // by default, always consider overwriting the background symbol
      overwritableTypes.add("O");

      if (split.length == 4) {
        try {
          priority = Double.parseDouble(split[3].trim());
        } catch(NumberFormatException e) {
          throw new IllegalArgumentException("ERROR: Invalid line " + lineCount + " in regexner file " + mapping + ": \"" + line + "\"!", e);

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