JsonWriter

Class Overview

Writes a JSON (RFC 4627) 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(boolean) 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(String) with the property's value. Write property values with the appropriate value(boolean) 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 write JSON on Android?",
     "geo": null,
     "user": {
       "name": "android_newb",
       "followers_count": 41
      
   },
   {
     "id": 912345678902,
     "text": "@android_newb just use android.util.JsonWriter!",
     "geo": [50.454722, -104.606667],
     "user": {
       "name": "jesse",
       "followers_count": 2
     }
   }
 ]}

This code encodes the above structure:

   public void writeJsonStream(OutputStream out, List messages) throws IOException {
     JsonWriter writer = new JsonWriter(new OutputStreamWriter(out, "UTF-8"));
     writer.setIndent("  ");
     writeMessagesArray(writer, messages);
     writer.close();
   

   public void writeMessagesArray(JsonWriter writer, List 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 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 IllegalStateException.

Summary

Public Constructors
	JsonWriter(Writer out) Creates a new instance that writes a JSON-encoded stream to out.

Public Methods
JsonWriter	beginArray() Begins encoding a new array.
JsonWriter	beginObject() Begins encoding a new object.
void	close() Flushes and closes this writer and the underlying Writer.
JsonWriter	endArray() Ends encoding the current array.
JsonWriter	endObject() Ends encoding the current object.
void	flush() Ensures all buffered data is written to the underlying Writer and flushes that writer.
boolean	isLenient() Returns true if this writer has relaxed syntax rules.
JsonWriter	name(String name) Encodes the property name.
JsonWriter	nullValue() Encodes null.
void	setIndent(String indent) Sets the indentation string to be repeated for each level of indentation in the encoded document.
void	setLenient(boolean lenient) Configure this writer to relax its syntax rules.
JsonWriter	value(double value) Encodes value.
JsonWriter	value(long value) Encodes value.
JsonWriter	value(Number value) Encodes value.
JsonWriter	value(boolean value) Encodes value.
JsonWriter	value(String value) Encodes value.

[Expand] Inherited Methods
From class java.lang.Object Object clone() Creates and returns a copy of this Object. boolean equals(Object o) Compares this instance with the specified object and indicates if they are equal. void finalize() Invoked when the garbage collector has detected that this instance is no longer reachable. final Class<?> getClass() Returns the unique instance of Class that represents this object's class. int hashCode() Returns an integer hash code for this object. final void notify() Causes a thread which is waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up. final void notifyAll() Causes all threads which are waiting on this object's monitor (by means of calling one of the wait() methods) to be woken up. String toString() Returns a string containing a concise, human-readable description of this object. final void wait() Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object. final void wait(long millis, int nanos) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires. final void wait(long millis) Causes the calling thread to wait until another thread calls the notify() or notifyAll() method of this object or until the specified timeout expires.
From interface java.io.Closeable abstract void close() Closes the object and release any system resources it holds.
From interface java.lang.AutoCloseable abstract void close() Closes the object and release any system resources it holds.