google/gson · error · JsonSyntaxException

Failed parsing '" + s + "' as SQL Date; at path " + in.getPr

Error message

Failed parsing '" + s + "' as SQL Date; at path " + in.getPreviousPath()

What it means

SqlDateTypeAdapter parses the JSON string with SimpleDateFormat("MMM d, yyyy") (e.g. 'Jan 1, 2024'). A ParseException is wrapped as JsonSyntaxException. The format is locale and timezone sensitive and is synchronized on the adapter.

Source

Thrown at gson/src/main/java/com/google/gson/internal/sql/SqlDateTypeAdapter.java:69

  private final DateFormat format = new SimpleDateFormat("MMM d, yyyy");

  private SqlDateTypeAdapter() {}

  @Override
  public java.sql.Date read(JsonReader in) throws IOException {
    if (in.peek() == JsonToken.NULL) {
      in.nextNull();
      return null;
    }
    String s = in.nextString();
    synchronized (this) {
      TimeZone originalTimeZone = format.getTimeZone(); // Save the original time zone
      try {
        Date utilDate = format.parse(s);
        return new java.sql.Date(utilDate.getTime());
      } catch (ParseException e) {
        throw new JsonSyntaxException(
            "Failed parsing '" + s + "' as SQL Date; at path " + in.getPreviousPath(), e);
      } finally {
        format.setTimeZone(originalTimeZone); // Restore the original time zone after parsing
      }
    }
  }

  @Override
  public void write(JsonWriter out, java.sql.Date value) throws IOException {
    if (value == null) {
      out.nullValue();
      return;
    }
    String dateString;
    synchronized (this) {
      dateString = format.format(value);
    }
    out.value(dateString);

View on GitHub (pinned to 8b8628c656)

Solutions

  1. Provide the date string in 'MMM d, yyyy' form, matching the default adapter.
  2. Register a custom TypeAdapter<java.sql.Date> using the format your producer emits (e.g. 'yyyy-MM-dd') and the desired Locale/TimeZone.
  3. Deserialize as java.util.Date or java.time.LocalDate instead and convert, if the SQL type is not essential.

Example fix

// before
java.sql.Date d = gson.fromJson("\"2024-01-01\"", java.sql.Date.class);

// after
Gson gson = new GsonBuilder().registerTypeAdapter(java.sql.Date.class, new TypeAdapter<java.sql.Date>() {
    private final java.text.DateFormat f = new java.text.SimpleDateFormat("yyyy-MM-dd");
    @Override public java.sql.Date read(JsonReader in) throws IOException { return java.sql.Date.valueOf(in.nextString()); }
    @Override public void write(JsonWriter out, java.sql.Date v) throws IOException { out.value(v.toString()); }
}).create();
Defensive patterns

Strategy: validation

Validate before calling

boolean isSqlDateParsable(String s) {
  if (s == null) return false;
  try { java.text.DateFormat f = new java.text.SimpleDateFormat("MMM d, yyyy", Locale.ENGLISH); f.parse(s); return true; }
  catch (java.text.ParseException e) { return false; }
}

Type guard

static boolean matchesDefaultSqlDateFormat(String s) {
  return s != null && s.matches("[A-Z][a-z]{2} \\d{1,2}, \\d{4}");
}

Try / catch

try {
  java.sql.Date d = gson.fromJson(json, java.sql.Date.class);
} catch (JsonSyntaxException e) {
  // parse with a custom format adapter instead
}

Prevention

When it happens

Trigger: Deserializing a JSON value into a java.sql.Date field where the string is not in the expected 'MMM d, yyyy' format (e.g. '2024-01-01', ISO format, or a locale-incompatible month abbreviation).

Common situations: Producer emits ISO-8601 or 'yyyy-MM-dd' but Gson's sql.Date adapter expects the long month form; running under a non-English locale where 'Jan' is not a valid month; or mismatched date conventions between layers.

Related errors

AI-assisted analysis of google/gson@8b8628c656 (2026-08-04). Data as JSON: /data/errors/6f4ff1629ab21a3b.json. Report an issue: GitHub.