languagetool-org/languagetool · error · RuntimeException

Required key '${key}' not found in properties

Error message

Required key '${key}' not found in properties

What it means

DatabaseHandler.getProperty requires that a database configuration key be present in the loaded Properties object; if Properties.getProperty returns null it throws a RuntimeException naming the missing key. It backs the dbUrl, dbUser, and dbPassword lookups, so any missing DB connection property aborts startup.

Source

Thrown at languagetool-wikipedia/src/main/java/org/languagetool/dev/dumpcheck/DatabaseHandler.java:87

      conn = DriverManager.getConnection(dbUrl, dbUser, dbPassword);
      insertSt = conn.prepareStatement(insertSql);
    } catch (SQLException | IOException e) {
      throw new RuntimeException(e);
    }
    contextTools = new ContextTools();
    contextTools.setContextSize(MAX_CONTEXT_LENGTH);
    contextTools.setErrorMarker(MARKER_START, MARKER_END);
    contextTools.setEscapeHtml(false);
    smallContextTools = new ContextTools();
    smallContextTools.setContextSize(SMALL_CONTEXT_LENGTH);
    smallContextTools.setErrorMarker(MARKER_START, MARKER_END);
    smallContextTools.setEscapeHtml(false);
  }

  private String getProperty(Properties prop, String key) {
    String value = prop.getProperty(key);
    if (value == null) {
      throw new RuntimeException("Required key '" + key + "' not found in properties");
    }
    return value;
  }

  @Override
  protected void handleResult(Sentence sentence, List<RuleMatch> ruleMatches, Language language) {
    try {
      java.sql.Date nowDate = new java.sql.Date(new Date().getTime());
      for (RuleMatch match : ruleMatches) {
        String smallContext = smallContextTools.getContext(match.getFromPos(), match.getToPos(), sentence.getText());
        insertSt.setString(1, language.getShortCode());
        Rule rule = match.getRule();
        insertSt.setString(2, rule.getId());
        insertSt.setString(3, rule.getCategory().getName());
        if (rule instanceof AbstractPatternRule) {
          AbstractPatternRule patternRule = (AbstractPatternRule) rule;
          insertSt.setString(4, patternRule.getSubId());
        } else {

View on GitHub (pinned to 2e990059ce)

Solutions

1. Open the properties file and add the exact key named in the message (e.g. dbUrl=jdbc:mysql://...)
2. Check key spelling against what DatabaseHandler expects
3. Confirm the -d option points to the intended properties file and that it loaded non-empty content

Example fix

// before (db.properties)
databaseUrl=jdbc:mysql://localhost/wiki
// after
dbUrl=jdbc:mysql://localhost/wiki
dbUser=ltuser
dbPassword=secret

Properties p = new Properties();
try (FileInputStream in = new FileInputStream(propFile)) { p.load(in); }
for (String key : new String[]{"dbUrl", "dbUser", "dbPassword"}) {
  if (p.getProperty(key) == null) throw new IllegalStateException("Missing required key: " + key);
}

static String requireProp(Properties p, String key) {
  String v = p.getProperty(key);
  if (v == null || v.trim().isEmpty()) throw new IllegalStateException("Missing/empty key: " + key);
  return v;
}

try {
  handler = new DatabaseHandler(props);
} catch (RuntimeException e) {
  if (e.getMessage() != null && e.getMessage().contains("not found in properties")) {
    System.err.println("Fix your properties file: " + e.getMessage()); System.exit(2);
  } else throw e;
}

When it happens

Trigger: The -d properties file passed to the checker lacks dbUrl, dbUser, or dbPassword, the key is misspelled, or the file is empty/loaded from the wrong path.

Common situations: Copying an old config template missing new keys; typos like 'databaseUrl' vs 'dbUrl'; loading a default/empty properties file because the -d option pointed elsewhere.

Understand the failure class

Background: "is required", "must be set", "missing required field": configuration validation errors across open-source libraries — this error's family across 36 libraries.

Related errors

• No rules are active. Please make sure your rule ids (<option
• List of language models is empty
• suppressMisspelledMatch must be a valid regex
• suppressMisspelledSuggestions must be a valid regex
• ApostropheTypeFilter: Index out of bounds in

AI-assisted analysis of languagetool-org/languagetool@2e990059ce (2026-09-06). Data as JSON: /api/errors/22d3c5d9e53422ab. Report an issue: GitHub.