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

All Implemented Interfaces:

java.io.Closeable, java.io.Flushable, java.lang.AutoCloseable

Direct Known Subclasses:

JsonTreeWriter
```
public class JsonWriter
extends java.lang.Object
implements java.io.Closeable, java.io.Flushable
```
Writes a JSON (RFC 8259) 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. 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().
Configuration
The behavior of this writer can be customized with the following methods:
- setFormattingStyle(FormattingStyle), the default is FormattingStyle.COMPACT
- setHtmlSafe(boolean), by default HTML characters are not escaped in the JSON output
- setStrictness(Strictness), the default is Strictness.LEGACY_STRICT
- setSerializeNulls(boolean), by default null is serialized
The default configuration of JsonWriter instances used internally by the Gson class differs, and can be adjusted with the various GsonBuilder methods.
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.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.
Since:

1.6

Field Summary

Fields
Modifier and Type	Field	Description
`private java.lang.String`	`deferredName`
`private java.lang.String`	`formattedColon`
`private java.lang.String`	`formattedComma`
`private FormattingStyle`	`formattingStyle`
`private static java.lang.String[]`	`HTML_SAFE_REPLACEMENT_CHARS`
`private boolean`	`htmlSafe`
`private java.io.Writer`	`out`	The JSON output destination
`private static java.lang.String[]`	`REPLACEMENT_CHARS`
`private boolean`	`serializeNulls`
`private int[]`	`stack`
`private int`	`stackSize`
`private Strictness`	`strictness`
`private boolean`	`usesEmptyNewlineAndIndent`
`private static java.util.regex.Pattern`	`VALID_JSON_NUMBER_PATTERN`

Constructor Summary

Constructors
Constructor Description

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

Method Summary

All Methods Static Methods Instance Methods Concrete Methods Deprecated Methods
Modifier and Type	Method	Description
`private static boolean`	`alwaysCreatesValidJsonNumber(java.lang.Class<? extends java.lang.Number> c)`	Returns whether the `toString()` of `c` will always return a valid JSON number.
`private void`	`beforeName()`	Inserts any necessary separators and whitespace before a name.
`private void`	`beforeValue()`	Inserts any necessary separators and whitespace before a literal value, inline array, or inline object.
`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`.
`private JsonWriter`	`closeScope(int empty, int nonempty, char closeBracket)`	Closes the current scope by appending any necessary whitespace and the given bracket.
`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.
`FormattingStyle`	`getFormattingStyle()`	Returns the pretty printing style used by this writer.
`boolean`	`getSerializeNulls()`	Returns true if object members are serialized when their value is null.
`Strictness`	`getStrictness()`	Returns the strictness of this 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 the `Strictness` of this writer is equal to `Strictness.LENIENT`.
`JsonWriter`	`jsonValue(java.lang.String value)`	Writes `value` directly to the writer without quoting or escaping.
`JsonWriter`	`name(java.lang.String name)`	Encodes the property name.
`private void`	`newline()`
`JsonWriter`	`nullValue()`	Encodes `null`.
`private JsonWriter`	`openScope(int empty, char openBracket)`	Enters a new scope by appending any necessary whitespace and the given bracket.
`private int`	`peek()`	Returns the value on the top of the stack.
`private void`	`push(int newTop)`
`private void`	`replaceTop(int topOfStack)`	Replace the value on the top of the stack with the given value.
`void`	`setFormattingStyle(FormattingStyle formattingStyle)`	Sets the formatting style to be used in the encoded document.
`void`	`setHtmlSafe(boolean htmlSafe)`	Configures this writer to emit JSON that's safe for direct inclusion in HTML and XML documents.
`void`	`setIndent(java.lang.String indent)`	Sets the indentation string to be repeated for each level of indentation in the encoded document.
`void`	`setLenient(boolean lenient)`	Deprecated. Please use `setStrictness(Strictness)` instead.
`void`	`setSerializeNulls(boolean serializeNulls)`	Sets whether object members are serialized when their value is null.
`void`	`setStrictness(Strictness strictness)`	Configures how strict this writer is with regard to the syntax rules specified in RFC 8259.
`private void`	`string(java.lang.String value)`
`JsonWriter`	`value(boolean value)`	Encodes `value`.
`JsonWriter`	`value(double value)`	Encodes `value`.
`JsonWriter`	`value(float value)`	Encodes `value`.
`JsonWriter`	`value(long value)`	Encodes `value`.
`JsonWriter`	`value(java.lang.Boolean value)`	Encodes `value`.
`JsonWriter`	`value(java.lang.Number value)`	Encodes `value`.
`JsonWriter`	`value(java.lang.String value)`	Encodes `value`.
`private void`	`writeDeferredName()`

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

- Field Detail
  - VALID_JSON_NUMBER_PATTERN
```
private static final java.util.regex.Pattern VALID_JSON_NUMBER_PATTERN
```
  - REPLACEMENT_CHARS
```
private static final java.lang.String[] REPLACEMENT_CHARS
```
  - HTML_SAFE_REPLACEMENT_CHARS
```
private static final java.lang.String[] HTML_SAFE_REPLACEMENT_CHARS
```
  - out
```
private final java.io.Writer out
```
    The JSON output destination
  - stack
```
private int[] stack
```
  - stackSize
```
private int stackSize
```
  - formattingStyle
```
private FormattingStyle formattingStyle
```
  - formattedColon
```
private java.lang.String formattedColon
```
  - formattedComma
```
private java.lang.String formattedComma
```
  - usesEmptyNewlineAndIndent
```
private boolean usesEmptyNewlineAndIndent
```
  - strictness
```
private Strictness strictness
```
  - htmlSafe
```
private boolean htmlSafe
```
  - deferredName
```
private java.lang.String deferredName
```
  - serializeNulls
```
private boolean serializeNulls
```
- Constructor Detail
  - JsonWriter
```
public JsonWriter(java.io.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 final void setIndent(java.lang.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.
    This is a convenience method which overwrites any previously set formatting style with either FormattingStyle.COMPACT if the given indent string is empty, or FormattingStyle.PRETTY with the given indent if not empty.
    
    Parameters:
    
    indent - a string containing only whitespace.
  - setFormattingStyle
```
public final void setFormattingStyle(FormattingStyle formattingStyle)
```
    Sets the formatting style to be used in the encoded document.
    The formatting style specifies for example the indentation string to be repeated for each level of indentation, or the newline style, to accommodate various OS styles.
    
    Parameters:
    
    formattingStyle - the formatting style to use, must not be null.
    
    Since:
    
    2.11.0
    
    See Also:
    
    getFormattingStyle()
  - getFormattingStyle
```
public final FormattingStyle getFormattingStyle()
```
    Returns the pretty printing style used by this writer.
    
    Returns:
    
    the FormattingStyle that will be used.
    
    Since:
    
    2.11.0
    
    See Also:
    
    setFormattingStyle(FormattingStyle)
  - setLenient
```
@Deprecated
public final void setLenient(boolean lenient)
```
    Deprecated.
    Please use setStrictness(Strictness) instead. JsonWriter.setLenient(true) should be replaced by JsonWriter.setStrictness(Strictness.LENIENT) and JsonWriter.setLenient(false) should be replaced by JsonWriter.setStrictness(Strictness.LEGACY_STRICT).
    However, if you used setLenient(false) before, you might prefer Strictness.STRICT now instead.
    
    Sets the strictness of this writer.
    
    Parameters:
    
    lenient - whether this writer should be lenient. If true, the strictness is set to Strictness.LENIENT. If false, the strictness is set to Strictness.LEGACY_STRICT.
    
    See Also:
    
    setStrictness(Strictness)
  - isLenient
```
public boolean isLenient()
```
    Returns true if the Strictness of this writer is equal to Strictness.LENIENT.
    
    See Also:
    
    getStrictness()
  - setStrictness
```
public final void setStrictness(Strictness strictness)
```
    Configures how strict this writer is with regard to the syntax rules specified in RFC 8259. By default, Strictness.LEGACY_STRICT is used.
    
    Strictness.STRICT & Strictness.LEGACY_STRICT
    The behavior of these is currently identical. In these strictness modes, the writer only writes JSON in accordance with RFC 8259.
    Strictness.LENIENT
    This mode relaxes the behavior of the writer to allow the writing of NaNs and infinities. It also allows writing multiple top level values.
    
    Parameters:
    
    strictness - the new strictness of this writer. May not be null.
    
    Since:
    
    2.11.0
    
    See Also:
    
    getStrictness()
  - getStrictness
```
public final Strictness getStrictness()
```
    Returns the strictness of this writer.
    
    Since:
    
    2.11.0
    
    See Also:
    
    setStrictness(Strictness)
  - setHtmlSafe
```
public final void setHtmlSafe(boolean htmlSafe)
```
    Configures 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.
    
    See Also:
    
    isHtmlSafe()
  - isHtmlSafe
```
public final boolean isHtmlSafe()
```
    Returns true if this writer writes JSON that's safe for inclusion in HTML and XML documents.
    
    See Also:
    
    setHtmlSafe(boolean)
  - setSerializeNulls
```
public final void setSerializeNulls(boolean serializeNulls)
```
    Sets whether object members are serialized when their value is null. This has no impact on array elements. The default is true.
    
    See Also:
    
    getSerializeNulls()
  - getSerializeNulls
```
public final boolean getSerializeNulls()
```
    Returns true if object members are serialized when their value is null. This has no impact on array elements. The default is true.
    
    See Also:
    
    setSerializeNulls(boolean)
  - beginArray
```
public JsonWriter beginArray()
                      throws java.io.IOException
```
    Begins encoding a new array. Each call to this method must be paired with a call to endArray().
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.io.IOException
  - endArray
```
public JsonWriter endArray()
                    throws java.io.IOException
```
    Ends encoding the current array.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.io.IOException
  - beginObject
```
public JsonWriter beginObject()
                       throws java.io.IOException
```
    Begins encoding a new object. Each call to this method must be paired with a call to endObject().
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.io.IOException
  - endObject
```
public JsonWriter endObject()
                     throws java.io.IOException
```
    Ends encoding the current object.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.io.IOException
  - openScope
```
private JsonWriter openScope(int empty,
                             char openBracket)
                      throws java.io.IOException
```
    Enters a new scope by appending any necessary whitespace and the given bracket.
    
    Throws:
    
    java.io.IOException
  - closeScope
```
private JsonWriter closeScope(int empty,
                              int nonempty,
                              char closeBracket)
                       throws java.io.IOException
```
    Closes the current scope by appending any necessary whitespace and the given bracket.
    
    Throws:
    
    java.io.IOException
  - push
```
private void push(int newTop)
```
  - peek
```
private int peek()
```
    Returns the value on the top of the stack.
  - replaceTop
```
private void replaceTop(int topOfStack)
```
    Replace the value on the top of the stack with the given value.
  - name
```
public JsonWriter name(java.lang.String name)
                throws java.io.IOException
```
    Encodes the property name.
    
    Parameters:
    
    name - the name of the forthcoming value. May not be null.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.io.IOException
  - writeDeferredName
```
private void writeDeferredName()
                        throws java.io.IOException
```
    Throws:
    
    java.io.IOException
  - value
```
public JsonWriter value(java.lang.String value)
                 throws java.io.IOException
```
    Encodes value.
    
    Parameters:
    
    value - the literal string value, or null to encode a null literal.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.io.IOException
  - value
```
public JsonWriter value(boolean value)
                 throws java.io.IOException
```
    Encodes value.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.io.IOException
  - value
```
public JsonWriter value(java.lang.Boolean value)
                 throws java.io.IOException
```
    Encodes value.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.io.IOException
    
    Since:
    
    2.7
  - value
```
public JsonWriter value(float value)
                 throws java.io.IOException
```
    Encodes value.
    
    Parameters:
    
    value - a finite value, or if lenient, also NaN or infinity.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.lang.IllegalArgumentException - if the value is NaN or Infinity and this writer is not lenient.
    
    java.io.IOException
    
    Since:
    
    2.9.1
  - value
```
public JsonWriter value(double value)
                 throws java.io.IOException
```
    Encodes value.
    
    Parameters:
    
    value - a finite value, or if lenient, also NaN or infinity.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.lang.IllegalArgumentException - if the value is NaN or Infinity and this writer is not lenient.
    
    java.io.IOException
  - value
```
public JsonWriter value(long value)
                 throws java.io.IOException
```
    Encodes value.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.io.IOException
  - value
```
public JsonWriter value(java.lang.Number value)
                 throws java.io.IOException
```
    Encodes value. The value is written by directly writing the Object.toString() result to JSON. Implementations must make sure that the result represents a valid JSON number.
    
    Parameters:
    
    value - a finite value, or if lenient, also NaN or infinity.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.lang.IllegalArgumentException - if the value is NaN or Infinity and this writer is not lenient; or if the toString() result is not a valid JSON number.
    
    java.io.IOException
  - nullValue
```
public JsonWriter nullValue()
                     throws java.io.IOException
```
    Encodes null.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.io.IOException
  - jsonValue
```
public JsonWriter jsonValue(java.lang.String value)
                     throws java.io.IOException
```
    Writes value directly to the writer without quoting or escaping. This might not be supported by all implementations, if not supported an UnsupportedOperationException is thrown.
    
    Parameters:
    
    value - the literal string value, or null to encode a null literal.
    
    Returns:
    
    this writer.
    
    Throws:
    
    java.lang.UnsupportedOperationException - if this writer does not support writing raw JSON values.
    
    java.io.IOException
    
    Since:
    
    2.4
  - flush
```
public void flush()
           throws java.io.IOException
```
    Ensures all buffered data is written to the underlying Writer and flushes that writer.
    
    Specified by:
    
    flush in interface java.io.Flushable
    
    Throws:
    
    java.io.IOException
  - close
```
public void close()
           throws java.io.IOException
```
    Flushes and closes this writer and the underlying Writer.
    
    Specified by:
    
    close in interface java.lang.AutoCloseable
    
    Specified by:
    
    close in interface java.io.Closeable
    
    Throws:
    
    java.io.IOException - if the JSON document is incomplete.
  - alwaysCreatesValidJsonNumber
```
private static boolean alwaysCreatesValidJsonNumber(java.lang.Class<? extends java.lang.Number> c)
```
    Returns whether the toString() of c will always return a valid JSON number.
  - string
```
private void string(java.lang.String value)
             throws java.io.IOException
```
    Throws:
    
    java.io.IOException
  - newline
```
private void newline()
              throws java.io.IOException
```
    Throws:
    
    java.io.IOException
  - beforeName
```
private void beforeName()
                 throws java.io.IOException
```
    Inserts any necessary separators and whitespace before a name. Also adjusts the stack to expect the name's value.
    
    Throws:
    
    java.io.IOException
  - beforeValue
```
private void beforeValue()
                  throws java.io.IOException
```
    Inserts any necessary separators and whitespace before a literal value, inline array, or inline object. Also adjusts the stack to expect either a closing bracket or another element.
    
    Throws:
    
    java.io.IOException

Class JsonWriter

Encoding JSON

Configuration

Example

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

VALID_JSON_NUMBER_PATTERN

REPLACEMENT_CHARS

HTML_SAFE_REPLACEMENT_CHARS

out

stack

stackSize

formattingStyle

formattedColon

formattedComma

usesEmptyNewlineAndIndent

strictness

htmlSafe

deferredName

serializeNulls

Constructor Detail

JsonWriter

Method Detail

setIndent

setFormattingStyle

getFormattingStyle

setLenient

isLenient

setStrictness

getStrictness

setHtmlSafe

isHtmlSafe

setSerializeNulls

getSerializeNulls

beginArray

endArray

beginObject

endObject

openScope

closeScope

push

peek

replaceTop

name

writeDeferredName

value

value

value

value

value

value

value

nullValue

jsonValue

flush

close

alwaysCreatesValidJsonNumber

string

newline

beforeName

beforeValue