JsonWriter

abstract class JsonWriter : Closeable, Flushable

Writes a JSON (RFC 7159) encoded value to a stream, one token at a time. The stream includes both literal values (strings, numbers, booleans and nulls) as well as the begin and end delimiters of objects and arrays.

Encoding JSON

To encode your data as JSON, create a new JsonWriter. Each JSON document must contain one top-level array or object. Call methods on the writer as you walk the structure's contents, nesting arrays and objects as necessary:

To write arrays, first call beginArray. Write each of the array's elements with the appropriate value methods or by nesting other arrays and objects. Finally close the array using endArray.
To write objects, first call beginObject. Write each of the object's properties by alternating calls to name with the property's value. Write property values with the appropriate value method or by nesting other objects or arrays. Finally close the object using endObject.

Example

Suppose we'd like to encode a stream of messages such as the following:


[
  {
    "id": 912345678901,
    "text": "How do I stream JSON in Java?",
    "geo": null,
    "user": {
      "name": "json_newb",
      "followers_count": 41
     }
  },
  {
    "id": 912345678902,
    "text": "@json_newb just use JsonWriter!",
    "geo": [50.454722, -104.606667],
    "user": {
      "name": "jesse",
      "followers_count": 2
    }
  }
]

This code encodes the above structure:


public void writeJsonStream(BufferedSink sink, List<Message> messages) throws IOException {
  JsonWriter writer = JsonWriter.of(sink);
  writer.setIndent("  ");
  writeMessagesArray(writer, messages);
  writer.close();
}

public void writeMessagesArray(JsonWriter writer, List<Message> messages) throws IOException {
  writer.beginArray();
  for (Message message : messages) {
    writeMessage(writer, message);
  }
  writer.endArray();
}

public void writeMessage(JsonWriter writer, Message message) throws IOException {
  writer.beginObject();
  writer.name("id").value(message.getId());
  writer.name("text").value(message.getText());
  if (message.getGeo() != null) {
    writer.name("geo");
    writeDoublesArray(writer, message.getGeo());
  } else {
    writer.name("geo").nullValue();
  }
  writer.name("user");
  writeUser(writer, message.getUser());
  writer.endObject();
}

public void writeUser(JsonWriter writer, User user) throws IOException {
  writer.beginObject();
  writer.name("name").value(user.getName());
  writer.name("followers_count").value(user.getFollowersCount());
  writer.endObject();
}

public void writeDoublesArray(JsonWriter writer, List<Double> doubles) throws IOException {
  writer.beginArray();
  for (Double value : doubles) {
    writer.value(value);
  }
  writer.endArray();
}

Each JsonWriter may be used to write a single JSON stream. Instances of this class are not thread safe. Calls that would result in a malformed JSON string will fail with an .