JsonWriter

Summary: Ctors | Methods | Inherited Methods

public final class JsonWriter
extends Object implements Closeable

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<Message> 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<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 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(Number value)` Encodes `value`.
`JsonWriter`	`value(boolean value)` Encodes `value`.
`JsonWriter`	`value(long value)` Encodes `value`.
`JsonWriter`	`value(String value)` Encodes `value`.

Inherited methods

From class java.lang.Object

`Object`	`clone()` Creates and returns a copy of this object.
`boolean`	`equals(Object obj)` Indicates whether some other object is "equal to" this one.
`void`	`finalize()` Called by the garbage collector on an object when garbage collection determines that there are no more references to the object.
`final Class<?>`	`getClass()` Returns the runtime class of this `Object`.
`int`	`hashCode()` Returns a hash code value for the object.
`final void`	`notify()` Wakes up a single thread that is waiting on this object's monitor.
`final void`	`notifyAll()` Wakes up all threads that are waiting on this object's monitor.
`String`	`toString()` Returns a string representation of the object.
`final void`	`wait(long timeoutMillis, int nanos)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait(long timeoutMillis)` Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed.
`final void`	`wait()` Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

From interface java.io.Closeable


      close()

Closes this stream and releases any system resources associated with it.

From interface java.lang.AutoCloseable


      close()

Closes this resource, relinquishing any underlying resources.

Public constructors

public JsonWriter (Writer out)

Creates a new instance that writes a JSON-encoded stream to out. For best performance, ensure Writer is buffered; wrapping in BufferedWriter if necessary.

Parameters
`out`	`Writer`

Public methods

close

public void close ()

Flushes and closes this writer and the underlying Writer.

Throws
`IOException`	if the JSON document is incomplete.

flush

public void flush ()

Ensures all buffered data is written to the underlying Writer and flushes that writer.

Throws
`IOException`

isLenient

public boolean isLenient ()

Returns true if this writer has relaxed syntax rules.

Returns
`boolean`

name

public JsonWriter name (String name)

Encodes the property name.

Parameters
`name`	`String`: the name of the forthcoming value. May not be null.

Returns
`JsonWriter`	this writer.

Throws
`IOException`

setIndent

public void setIndent (String indent)

Sets the indentation string to be repeated for each level of indentation in the encoded document. If indent.isEmpty() the encoded document will be compact. Otherwise the encoded document will be more human-readable.

Parameters
`indent`	`String`: a string containing only whitespace.

setLenient

public void setLenient (boolean lenient)

Configure this writer to relax its syntax rules. By default, this writer only emits well-formed JSON as specified by RFC 4627. Setting the writer to lenient permits the following:

Top-level values of any type. With strict writing, the top-level value must be an object or an array.
Numbers may be NaNs or infinities.

Parameters
`lenient`	`boolean`

value

public JsonWriter value (String value)

Encodes value.

Parameters
`value`	`String`: the literal string value, or null to encode a null literal.

Returns
`JsonWriter`	this writer.

Throws
`IOException`