languagetool-org/languagetool · error · IOException

Checksum mismatch for the file '${path}': expected ${require

Error message

Checksum mismatch for the file '${path}': expected ${requiredHash}, got ${computedHash}

What it means

Tools.getStream reads a file fully, computes its SHA-256 hash, and compares it against a caller-supplied required hash before returning the data as a stream. An IOException with this message is thrown when the content has changed or the expected hash is wrong, guaranteeing callers never process tampered or stale data.

Source

Thrown at languagetool-core/src/main/java/org/languagetool/tools/Tools.java:285

    InputStream is = JLanguageTool.getDataBroker().getAsStream(path);
    if (is == null) {
      throw new IOException("Could not load file from classpath: '" + path + "'");
    }
    return is;
  }

  public static InputStream getStream(String path, String requiredHash) throws IOException, NoSuchAlgorithmException {
    byte[] data;

    try (InputStream is = getStream(path)) {
      data = is.readAllBytes();
    }

    MessageDigest md = MessageDigest.getInstance("SHA-256");
    String computedHash = HexFormat.of().formatHex(md.digest(data));

    if (!computedHash.equals(requiredHash)) {
      throw new IOException("Checksum mismatch for the file '" + path + "': expected " + requiredHash + ", got " + computedHash);
    }
    return new ByteArrayInputStream(data);
  }

  /**
   * Enable and disable rules of the given LanguageTool instance.
   * @param lt LanguageTool object
   * @param disabledRuleIds ids of the rules to be disabled
   * @param enabledRuleIds ids of the rules to be enabled
   * @param useEnabledOnly if set to {@code true}, disable all rules except those enabled explicitly
   */
  public static void selectRules(JLanguageTool lt, List<String> disabledRuleIds, List<String> enabledRuleIds, boolean useEnabledOnly) {
    Set<String> disabledRuleIdsSet = new HashSet<>();
    disabledRuleIdsSet.addAll(disabledRuleIds);
    Set<String> enabledRuleIdsSet = new HashSet<>();
    enabledRuleIdsSet.addAll(enabledRuleIds);
    selectRules(lt, Collections.emptySet(), Collections.emptySet(), disabledRuleIdsSet, enabledRuleIdsSet, useEnabledOnly, false);
  }

View on GitHub (pinned to 2e990059ce)

Solutions

1. Recompute the expected SHA-256 hash from the current file content (shasum -a 256 <path>) and pass that as requiredHash
2. Re-download or restore the original file from the trusted source that matches requiredHash
3. If the file legitimately changed, update the pinned hash in the calling code/config
4. Check for proxy or transfer corruption by re-fetching the file and comparing hashes

Example fix

// before
InputStream in = Tools.getStream(path, "abc123oldhash");
// after
String hash = HexFormat.of().formatHex(MessageDigest.getInstance("SHA-256").digest(Files.readAllBytes(Path.of(path))));
InputStream in = Tools.getStream(path, hash);

String actual = HexFormat.of().formatHex(MessageDigest.getInstance("SHA-256").digest(Files.readAllBytes(Path.of(path))));
if (!actual.equals(requiredHash)) throw new IOException("Checksum mismatch: " + path);
InputStream in = Tools.getStream(path, requiredHash);

try (InputStream in = Tools.getStream(path, requiredHash)) { ... } catch (IOException e) { if (e.getMessage().startsWith("Checksum mismatch")) { reDownloadFile(path); } else { throw e; } }

When it happens

Trigger: Calling Tools.getStream(path, requiredHash) where the file bytes changed after the expected hash was recorded, the hash was computed on a different file/version, or the hash string itself is malformed/outdated.

Common situations: Downloading cached language-model or resource files whose upstream content was updated; reusing a pinned hash across releases; manual edits to a data file after hashing.

Understand the failure class

Background: Checksum mismatch errors: "checksum verification failed", "digest mismatch", "expected vs actual checksum" — what they mean and how to fix them — this error's family across 41 libraries.

AI-assisted analysis of languagetool-org/languagetool@2e990059ce (2026-09-06). Data as JSON: /api/errors/34d436b4646eb3a9. Report an issue: GitHub.