google/gson · error · JsonSyntaxException

Did not consume the entire document.

Error message

Did not consume the entire document.

What it means

Thrown as JsonSyntaxException by JsonParser.parseReader(Reader) (JsonParser.java:112) after successfully parsing one top-level JSON value if the reader still has content — i.e. element is not JsonNull and jsonReader.peek() != JsonToken.END_DOCUMENT. It means the input contained more than a single top-level JSON document or had trailing tokens. (Trailing whitespace is fine; trailing tokens are not.)

Solutions

1. For NDJSON/streaming, parse one document per line or drive a JsonReader loop with parseReader(JsonReader) which does NOT enforce single-document consumption
2. Trim and inspect the raw input for trailing tokens before parsing
3. Verify the source emits exactly one top-level JSON value
4. If multiple documents are intentional, switch to the JsonReader overload and loop until END_DOCUMENT

Example fix

// before
JsonElement e = JsonParser.parseString(ndjsonLine); // fails if two docs on one line
// after (per-line NDJSON)
for (String line : raw.split("\n")) {
    if (!line.isBlank()) JsonParser.parseString(line);
}
// after (streaming, tolerates trailing docs)
try (JsonReader r = new JsonReader(new StringReader(raw))) {
    while (r.peek() != JsonToken.END_DOCUMENT) {
        JsonElement e = JsonParser.parseReader(r);
    }
}

// ensure exactly one top-level JSON value before parsing
String trimmed = raw.strip();
// simplest: parse and then re-peek via the JsonReader overload which does NOT enforce single-doc:
try (JsonReader r = new JsonReader(new StringReader(trimmed))) {
    JsonElement e = JsonParser.parseReader(r);
    // r.peek() == END_DOCUMENT here means no trailing tokens
}

try {
    JsonElement e = JsonParser.parseString(raw);
} catch (JsonSyntaxException ex) {
    if (ex.getMessage().contains("Did not consume the entire document")) {
        // trailing data: switch to per-line or JsonReader streaming parse
    }
}

When it happens

Trigger: Input with multiple concatenated top-level values or trailing characters: '{ }{ }', '1 2 3', '{}' followed by stray text, two JSON objects joined, or a value followed by a stray comma. Also feeding newline-delimited JSON (NDJSON) to parseString, which expects exactly one document.

Common situations: NDJSON/log streams read as a single document; a buffer that accidentally concatenated two responses; stray BOM or paste artifacts; a trailing comma after the top-level value.

Related errors

• Failed parsing JSON source
• See
• End of input
• Expected a long but was
• Failed parsing ' ' as BigInteger; at path

AI-assisted analysis of google/gson@310ac341f2 (2026-08-10). Data as JSON: /api/errors/2706ed57eb8d436a. Report an issue: GitHub.

Appendix: source

Thrown at gson/src/main/java/com/google/gson/JsonParser.java:112

  /**
   * Parses the complete JSON string provided by the reader into a parse tree. An exception is
   * thrown if the JSON string has multiple top-level JSON elements, or if there is trailing data.
   *
   * <p>The JSON data is parsed in {@linkplain JsonReader#setStrictness(Strictness) lenient mode}.
   *
   * @param reader JSON text
   * @return a parse tree of {@link JsonElement}s corresponding to the specified JSON
   * @throws JsonParseException if there is an IOException or if the specified text is not valid
   *     JSON
   * @since 2.8.6
   */
  public static JsonElement parseReader(Reader reader) throws JsonIOException, JsonSyntaxException {
    try {
      JsonReader jsonReader = new JsonReader(reader);
      JsonElement element = parseReader(jsonReader);
      if (!element.isJsonNull() && jsonReader.peek() != JsonToken.END_DOCUMENT) {
        throw new JsonSyntaxException("Did not consume the entire document.");
      }
      return element;
    } catch (MalformedJsonException | NumberFormatException e) {
      throw new JsonSyntaxException(e);
    } catch (IOException e) {
      throw new JsonIOException(e);
    }
  }

  /**
   * Returns the next value from the JSON stream as a parse tree. Unlike the other {@code parse}
   * methods, no exception is thrown if the JSON data has multiple top-level JSON elements, or if
   * there is trailing data.
   *
   * <p>If the {@linkplain JsonReader#getStrictness() strictness of the reader} is {@link
   * Strictness#STRICT}, that strictness will be used for parsing. Otherwise the strictness will be
   * temporarily changed to {@link Strictness#LENIENT} and will be restored once this method
   * returns.

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