What causes "Got error: ${error} - HTTP response code ${conn.getResponseCode()}" in languagetool-org/languagetool?

Read the embedded error body and HTTP status in the message to identify the server-side problem

languagetool-org/languagetool · error · RuntimeException

Got error: ${error} - HTTP response code ${conn.getResponseC

Error message

Got error: ${error} - HTTP response code ${conn.getResponseCode()}

What it means

RemoteLanguageTool.getMaxTextLength reads the server's /v2/maxtextlength endpoint; if the HTTP response is not the expected success code, it reads the error stream and throws a RuntimeException containing the server's error body and the HTTP status code. This means the request reached the server but the server rejected it.

Source

Thrown at languagetool-http-client/src/main/java/org/languagetool/remote/RemoteLanguageTool.java:226

      checkUrl = new URL(serverBaseUrl + V2_MAXTEXTLENGTH);
    } catch (MalformedURLException e) {
      throw new RuntimeException(e);
    }
    HttpURLConnection conn = getConnection(postData, checkUrl);
    try {
      if (conn.getResponseCode() == HttpURLConnection.HTTP_OK) {
        try (InputStream inputStream = conn.getInputStream()) {
          StringBuilder sb = new StringBuilder();
          try (InputStreamReader isr = new InputStreamReader(inputStream, "utf-8");
               BufferedReader br = new BufferedReader(isr)) {
            String line = br.readLine();
            return Integer.parseInt(line);
          }
        }
      } else {
        try (InputStream inputStream = conn.getErrorStream()) {
          String error = readStream(inputStream, "utf-8");
          throw new RuntimeException("Got error: " + error + " - HTTP response code " + conn.getResponseCode());
        }
      }
    } catch (ConnectException e) {
      throw new RuntimeException("Could not connect to server at " + serverBaseUrl, e);
    } catch (Exception e) {
      throw new RuntimeException(e);
    } finally {
      conn.disconnect();
    }
  }

  HttpURLConnection getConnection(byte[] postData, URL url) {
    try {
      HttpURLConnection conn = (HttpURLConnection) url.openConnection();
      conn.setDoOutput(true);
      conn.setInstanceFollowRedirects(false);
      conn.setRequestMethod("POST");
      conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

View on GitHub (pinned to 2e990059ce)

Solutions

Read the embedded error body and HTTP status in the message to identify the server-side problem
Verify serverBaseUrl points at a running LanguageTool server (try /v2/languages in a browser or curl)
Check server logs for the corresponding request failure
If behind a proxy, fix proxy/rate-limiting/auth configuration

Example fix

// before
RemoteLanguageTool lt = new RemoteLanguageTool("http://localhost:8081"); // wrong port, another app
// after
RemoteLanguageTool lt = new RemoteLanguageTool("http://localhost:8081"); // with LT running:
// curl -s http://localhost:8081/v2/maxtextlength  -> 200 with number

Defensive patterns

Strategy: retry

Validate before calling

HttpURLConnection probe = (HttpURLConnection) new URL(serverBaseUrl + "/v2/languages").openConnection();
probe.setConnectTimeout(3000);
if (probe.getResponseCode() != 200) throw new IllegalStateException("server not healthy");

Type guard

static boolean isLanguageToolServerUp(String baseUrl) {
  try {
    HttpURLConnection c = (HttpURLConnection) new URL(baseUrl + "/v2/languages").openConnection();
    c.setConnectTimeout(3000);
    return c.getResponseCode() == 200;
  } catch (IOException e) { return false; }
}

Try / catch

try {
  int max = lt.getMaxTextLength();
} catch (RuntimeException e) {
  if (e.getMessage().contains("Got error:")) {
    // parse embedded HTTP code and server body, retry with backoff or fail fast
  } else throw e;
}

Prevention

Health-check /v2/languages before calling the API
Check server logs whenever the error body/status appears
Bypass or correctly configure proxies for the LT host

When it happens

Trigger: Calling getMaxTextLength() against a server that returns a non-2xx response: wrong API endpoint path, server-side authentication failure, an HTTP 4xx/5xx from a proxy, or a non-LanguageTool service listening on the URL.

Common situations: Reverse proxy returning 502/503; wrong port pointing at another app; premium API endpoint hit without valid credentials; server overloaded returning errors.

Understand the failure class

Background: "API error: {status}" and "HTTP 401/403/404/429/5xx" errors: non-2xx HTTP responses explained — this error's family across 27 libraries.

Related errors

AI-assisted analysis of languagetool-org/languagetool@2e990059ce (2026-09-06). Data as JSON: /api/errors/aa323d18f43139c3. Report an issue: GitHub.