JsonReader

class JsonReader : Closeable

Reads a JSON (RFC 4627) encoded value as a stream of tokens. This stream includes both literal values (strings, numbers, booleans, and nulls) as well as the begin and end delimiters of objects and arrays. The tokens are traversed in depth-first order, the same order that they appear in the JSON document. Within JSON objects, name/value pairs are represented by a single token.

Parsing JSON

Next, create handler methods for each structure in your JSON text. You'll need a method for each object type and for each array type.

• Within array handling methods, first call beginArray to consume the array's opening bracket. Then create a while loop that accumulates values, terminating when hasNext is false. Finally, read the array's closing bracket by calling endArray.
• Within object handling methods, first call beginObject to consume the object's opening brace. Then create a while loop that assigns values to local variables based on their name. This loop should terminate when hasNext is false. Finally, read the object's closing brace by calling endObject.

When a nested object or array is encountered, delegate to the corresponding handler method.

When an unknown name is encountered, strict parsers should fail with an exception. Lenient parsers should call skipValue() to recursively skip the value's nested tokens, which may otherwise conflict.

If a value may be null, you should first check using peek(). Null literals can be consumed using either nextNull() or skipValue().

Example

<code>[
    {
      "id": 912345678901,
      "text": "How do I read JSON on Android?",
      "geo": null,
      "user": {
        "name": "android_newb",
        "followers_count": 41
       }
    },
    {
      "id": 912345678902,
      "text": "@android_newb just use android.util.JsonReader!",
      "geo": [50.454722, -104.606667],
      "user": {
        "name": "jesse",
        "followers_count": 2
      }
    }
  ]</code>

<code>public List&lt;Message&gt; readJsonStream(InputStream in) throws IOException {
      JsonReader reader = new JsonReader(new InputStreamReader(in, "UTF-8"));
      try {
        return readMessagesArray(reader);
      } finally {
        reader.close();
      }
    }
 
    public List&lt;Message&gt; readMessagesArray(JsonReader reader) throws IOException {
      List&lt;Message&gt; messages = new ArrayList&lt;Message&gt;();
 
      reader.beginArray();
      while (reader.hasNext()) {
        messages.add(readMessage(reader));
      }
      reader.endArray();
      return messages;
    }
 
    public Message readMessage(JsonReader reader) throws IOException {
      long id = -1;
      String text = null;
      User user = null;
      List&lt;Double&gt; geo = null;
 
      reader.beginObject();
      while (reader.hasNext()) {
        String name = reader.nextName();
        if (name.equals("id")) {
          id = reader.nextLong();
        } else if (name.equals("text")) {
          text = reader.nextString();
        } else if (name.equals("geo") &amp;&amp; reader.peek() != JsonToken.NULL) {
          geo = readDoublesArray(reader);
        } else if (name.equals("user")) {
          user = readUser(reader);
        } else {
          reader.skipValue();
        }
      }
      reader.endObject();
      return new Message(id, text, user, geo);
    }
 
    public List&lt;Double&gt; readDoublesArray(JsonReader reader) throws IOException {
      List&lt;Double&gt; doubles = new ArrayList&lt;Double&gt;();
 
      reader.beginArray();
      while (reader.hasNext()) {
        doubles.add(reader.nextDouble());
      }
      reader.endArray();
      return doubles;
    }
 
    public User readUser(JsonReader reader) throws IOException {
      String username = null;
      int followersCount = -1;
 
      reader.beginObject();
      while (reader.hasNext()) {
        String name = reader.nextName();
        if (name.equals("name")) {
          username = reader.nextString();
        } else if (name.equals("followers_count")) {
          followersCount = reader.nextInt();
        } else {
          reader.skipValue();
        }
      }
      reader.endObject();
      return new User(username, followersCount);
    }</code>

Number Handling

Each JsonReader may be used to read a single JSON stream. Instances of this class are not thread safe.

Summary

Public constructors

JsonReader(in: Reader!)

Public methods

fun beginArray(): Unit

fun beginObject(): Unit

fun close(): Unit

fun endArray(): Unit

fun endObject(): Unit

fun hasNext(): Boolean

fun isLenient(): Boolean

fun nextBoolean(): Boolean

fun nextDouble(): Double

fun nextInt(): Int

fun nextLong(): Long

fun nextName(): String!

fun nextNull(): Unit

fun nextString(): String!

fun peek(): JsonToken!

fun setLenient(lenient: Boolean): Unit

fun skipValue(): Unit

fun toString(): String