JsonWriter (jclouds 1.2.0 API)

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com.google.gson.stream
Class JsonWriter

java.lang.Object
  com.google.gson.stream.JsonWriter

All Implemented Interfaces:: Closeable

public final class JsonWriter
extends Object
implements Closeable
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(java.lang.String) 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(java.lang.String) with the property's value. Write property values with the appropriate value(java.lang.String) 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(OutputStream out, List<Message> messages) throws IOException {
     JsonWriter writer = new JsonWriter(new OutputStreamWriter(out, "UTF-8"));
     writer.setIndentSpaces(4);
     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.

Since:: 1.6
Author:: Jesse Wilson

Constructor Summary
`JsonWriter(Writer out)` Creates a new instance that writes a JSON-encoded stream to `out`.

Method Summary
`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`	`isHtmlSafe()` Returns true if this writer writes JSON that's safe for inclusion in HTML and XML documents.
`boolean`	`isLenient()` Returns true if this writer has relaxed syntax rules.
`JsonWriter`	`name(String name)` Encodes the property name.
`JsonWriter`	`nullValue()` Encodes `null`.
`void`	`setHtmlSafe(boolean htmlSafe)` Configure this writer to emit JSON that's safe for direct inclusion in HTML and XML documents.
`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(boolean value)` Encodes `value`.
`JsonWriter`	`value(double value)` Encodes `value`.
`JsonWriter`	`value(JsonLiteral value)` Writes `value` literally
`JsonWriter`	`value(long value)` Encodes `value`.
`JsonWriter`	`value(Number value)` Encodes `value`.
`JsonWriter`	`value(String value)` Encodes `value`.

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Constructor Detail

JsonWriter

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.

Method Detail

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 - 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.

isLenient

public boolean isLenient()

Returns true if this writer has relaxed syntax rules.

setHtmlSafe

public void setHtmlSafe(boolean htmlSafe)

Configure this writer to emit JSON that's safe for direct inclusion in HTML and XML documents. This escapes the HTML characters <, >, & and = before writing them to the stream. Without this setting, your XML/HTML encoder should replace these characters with the corresponding escape sequences.

isHtmlSafe

public boolean isHtmlSafe()

Returns true if this writer writes JSON that's safe for inclusion in HTML and XML documents.

beginArray

public JsonWriter beginArray()
                      throws IOException

Begins encoding a new array. Each call to this method must be paired with a call to endArray().

Returns:: this writer.
Throws:: IOException

endArray

public JsonWriter endArray()
                    throws IOException

Ends encoding the current array.

Returns:: this writer.
Throws:: IOException

beginObject

public JsonWriter beginObject()
                       throws IOException

Begins encoding a new object. Each call to this method must be paired with a call to endObject().

Returns:: this writer.
Throws:: IOException

endObject

public JsonWriter endObject()
                     throws IOException

Ends encoding the current object.

Returns:: this writer.
Throws:: IOException

name

public JsonWriter name(String name)
                throws IOException

Encodes the property name.

Parameters:: name - the name of the forthcoming value. May not be null.
Returns:: this writer.
Throws:: IOException

value

public JsonWriter value(String value)
                 throws IOException

Encodes value.

Parameters:: value - the literal string value, or null to encode a null literal.
Returns:: this writer.
Throws:: IOException

nullValue

public JsonWriter nullValue()
                     throws IOException

Encodes null.

Returns:: this writer.
Throws:: IOException

value

public JsonWriter value(JsonLiteral value)
                 throws IOException

Writes value literally

Returns:: this writer.
Throws:: IOException

value

public JsonWriter value(boolean value)
                 throws IOException

Encodes value.

Returns:: this writer.
Throws:: IOException

value

public JsonWriter value(double value)
                 throws IOException

Encodes value.

Parameters:: value - a finite value. May not be NaNs or infinities.
Returns:: this writer.
Throws:: IOException

value

public JsonWriter value(long value)
                 throws IOException

Encodes value.

Returns:: this writer.
Throws:: IOException

value

public JsonWriter value(Number value)
                 throws IOException

Encodes value.

Parameters:: value - a finite value. May not be NaNs or infinities.
Returns:: this writer.
Throws:: IOException

flush

public void flush()
           throws IOException

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

Throws:: IOException

close

public void close()
           throws IOException

Flushes and closes this writer and the underlying Writer.

Specified by:: close in interface Closeable

Throws:: IOException - if the JSON document is incomplete.

Overview

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com.google.gson.stream Class JsonWriter

Encoding JSON

Example

JsonWriter

setIndent

setLenient

isLenient

setHtmlSafe

isHtmlSafe

beginArray

endArray

beginObject

endObject

name

value

nullValue

value

value

value

value

value

flush

close

com.google.gson.stream
Class JsonWriter