stanfordnlp/CoreNLP · critical · javax.servlet.ServletException

File not found. Filename = " + filename

Error message

File not found. Filename = " + filename

What it means

During init(), NERServlet loads each configured classifier model via ServletContext.getResourceAsStream. If the stream is null — the resource '/WEB-INF/data/models/<classifier>' does not exist in the webapp — it throws ServletException naming the missing filename.

Solutions

1. Copy the required classifier model files into src/main/webapp/WEB-INF/data/models/ and rebuild the WAR
2. Match the classifier init-param names exactly to the filenames present in WEB-INF/data/models
3. Check the build (Maven/Gradle) isn't filtering/excluding model resources from the WAR
4. Verify inside the deployed webapp container (not just the source tree) that the resource resolves

Example fix

<!-- before -->
<init-param><param-name>classifiers</param-name><param-value>english.all.3class.distsim.crf.ser.gz</param-value></init-param>
<!-- after: also ensure the file exists -->
# cp english.all.3class.distsim.crf.ser.gz webapp/WEB-INF/data/models/
<init-param><param-name>classifiers</param-name><param-value>english.all.3class.distsim.crf.ser.gz</param-value></init-param>

for (String c : classifierNames) {
  if (getServletContext().getResourceAsStream("/WEB-INF/data/models/" + c) == null)
    throw new IllegalStateException("Model missing from WAR: " + c);
}

try { servlet.init(cfg); } catch (ServletException e) { if (e.getMessage().startsWith("File not found")) redeployWithModels(); }

When it happens

Trigger: init-param listing classifier model files that were never placed under the webapp's WEB-INF/data/models directory; misspelled model filenames; WAR packaging that excludes .ser/.gz model files.

Common situations: Building the WAR without the large model files (excluded by build config or .gitignore); renaming models on disk but not in the classifier init-param; deploying a slimmed distribution.

Understand the failure class

Background: 'Could not be found', 'does not exist', 'not found in database': the resource-not-found family when an ID, slug, key, or URI lookup comes back empty — this error's family across 20 libraries.

Related errors

• Couldn't load classifier from
• Invalid outputFormat setting.
• Invalid preserveSpacing setting.
• IO problem reading classifier.
• Could not find inside

AI-assisted analysis of stanfordnlp/CoreNLP@1b7edd19c4 (2026-09-10). Data as JSON: /api/errors/abc204fb1dde97d4. Report an issue: GitHub.

Appendix: source

Thrown at src/edu/stanford/nlp/ie/ner/webapp/NERServlet.java:74

    String path = getServletContext().getRealPath("/WEB-INF/data/models");
    for (String classifier : new File(path).list()) {
      classifiers.add(classifier);
    }
    // TODO: get this from somewhere more interesting?
    defaultClassifier = classifiers.get(0);

    for (String classifier : classifiers) {
      log(classifier);
    }

    ners = new HashMap<>();
    for (String classifier : classifiers) {
      CRFClassifier<CoreMap> model = null;
      String filename = "/WEB-INF/data/models/" + classifier;
      InputStream is = getServletConfig().getServletContext().getResourceAsStream(filename);

      if (is == null) {
        throw new ServletException("File not found. Filename = " + filename);
      }
      try {
        if (filename.endsWith(".gz")) {
          is = new BufferedInputStream(new GZIPInputStream(is));
        } else {
          is = new BufferedInputStream(is);
        }
        model = CRFClassifier.getClassifier(is);
      } catch (IOException e) {
        throw new ServletException("IO problem reading classifier.");
      } catch (ClassCastException e) {
        throw new ServletException("Classifier class casting problem.");
      } catch (ClassNotFoundException e) {
        throw new ServletException("Classifier class not found problem.");
      } finally {
        IOUtils.closeIgnoringExceptions(is);
      }
      ners.put(classifier, model);

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