JsonWriter
class JsonWriter : Closeable
kotlin.Any | |
↳ | android.util.JsonWriter |
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 newJsonWriter
. 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 usingendArray()
. - To write objects, first call
beginObject()
. Write each of the object's properties by alternating calls toname
with the property's value. Write property values with the appropriate #value method or by nesting other objects or arrays. Finally close the object usingendObject()
.
Example
Suppose we'd like to encode a stream of messages such as the following:<code>[ { "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 } } ]</code>
<code>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(); }</code>
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(out: Writer!) Creates a new instance that writes a JSON-encoded stream to |
Public methods | |
---|---|
JsonWriter! |
Begins encoding a new array. |
JsonWriter! |
Begins encoding a new object. |
Unit |
close() Flushes and closes this writer and the underlying |
JsonWriter! |
endArray() Ends encoding the current array. |
JsonWriter! |
Ends encoding the current object. |
Unit |
flush() Ensures all buffered data is written to the underlying |
Boolean |
Returns true if this writer has relaxed syntax rules. |
JsonWriter! |
Encodes the property name. |
JsonWriter! |
Encodes |
Unit |
Sets the indentation string to be repeated for each level of indentation in the encoded document. |
Unit |
setLenient(lenient: Boolean) Configure this writer to relax its syntax rules. |
JsonWriter! |
Encodes |
JsonWriter! |
Encodes |
JsonWriter! |
Encodes |
JsonWriter! |
Encodes |
JsonWriter! |
Encodes |
Public constructors
JsonWriter
JsonWriter(out: Writer!)
Creates a new instance that writes a JSON-encoded stream to out
. For best performance, ensure Writer
is buffered; wrapping in BufferedWriter
if necessary.
Public methods
beginArray
fun beginArray(): JsonWriter!
Begins encoding a new array. Each call to this method must be paired with a call to endArray
.
Return | |
---|---|
JsonWriter! |
this writer. |
beginObject
fun beginObject(): JsonWriter!
Begins encoding a new object. Each call to this method must be paired with a call to endObject
.
Return | |
---|---|
JsonWriter! |
this writer. |
close
fun close(): Unit
Flushes and closes this writer and the underlying Writer
.
Exceptions | |
---|---|
java.lang.Exception |
if this resource cannot be closed |
java.io.IOException |
if the JSON document is incomplete. |
endArray
fun endArray(): JsonWriter!
Ends encoding the current array.
Return | |
---|---|
JsonWriter! |
this writer. |
endObject
fun endObject(): JsonWriter!
Ends encoding the current object.
Return | |
---|---|
JsonWriter! |
this writer. |
flush
fun flush(): Unit
Ensures all buffered data is written to the underlying Writer
and flushes that writer.
isLenient
fun isLenient(): Boolean
Returns true if this writer has relaxed syntax rules.
name
fun name(name: String!): JsonWriter!
Encodes the property name.
Parameters | |
---|---|
name |
String!: the name of the forthcoming value. May not be null. |
Return | |
---|---|
JsonWriter! |
this writer. |
nullValue
fun nullValue(): JsonWriter!
Encodes null
.
Return | |
---|---|
JsonWriter! |
this writer. |
setIndent
fun setIndent(indent: String!): Unit
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
fun setLenient(lenient: Boolean): Unit
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
orinfinities
.
value
fun value(value: Boolean): JsonWriter!
Encodes value
.
Return | |
---|---|
JsonWriter! |
this writer. |
value
fun value(value: Double): JsonWriter!
Encodes value
.
Parameters | |
---|---|
value |
Double: a finite value. May not be NaNs or infinities unless this writer is lenient. |
Return | |
---|---|
JsonWriter! |
this writer. |
value
fun value(value: Number!): JsonWriter!
Encodes value
.
Parameters | |
---|---|
value |
Number!: a finite value. May not be NaNs or infinities unless this writer is lenient. |
Return | |
---|---|
JsonWriter! |
this writer. |
value
fun value(value: String!): JsonWriter!
Encodes value
.
Parameters | |
---|---|
value |
String!: the literal string value, or null to encode a null literal. |
Return | |
---|---|
JsonWriter! |
this writer. |
value
fun value(value: Long): JsonWriter!
Encodes value
.
Return | |
---|---|
JsonWriter! |
this writer. |