org.json

Class JSONWriter

java.lang.Object

org.json.JSONWriter

Direct Known Subclasses:

JSONStringer

public class JSONWriter
extends Object

JSONWriter provides a quick and convenient way of producing JSON text. The texts produced strictly conform to JSON syntax rules. No whitespace is added, so the results are ready for transmission or storage. Each instance of JSONWriter can produce one JSON text.

A JSONWriter instance provides a value method for appending values to the text, and a key method for adding keys before values in objects. There are array and endArray methods that make and bound array values, and object and endObject methods which make and bound object values. All of these methods return the JSONWriter instance, permitting a cascade style. For example,

 new JSONWriter(myWriter)
     .object()
         .key("JSON")
         .value("Hello, World!")
     .endObject();

which writes

 {"JSON":"Hello, World!"}

The first method called must be array or object. There are no methods for adding commas or colons. JSONWriter adds them for you. Objects and arrays can be nested up to 200 levels deep.

This can sometimes be easier than using a JSONObject to build a string.

Field Summary

Fields

Modifier and Type	Field and Description
protected char	mode The current mode.
protected Appendable	writer The writer that will receive the output.

Constructor Summary

Constructors

Constructor and Description
JSONWriter(Appendable w) Make a fresh JSONWriter.

Method Summary

Modifier and Type	Method and Description
JSONWriter	array() Begin appending a new array.
JSONWriter	endArray() End an array.
JSONWriter	endObject() End an object.
JSONWriter	key(String string) Append a key.
JSONWriter	object() Begin appending a new object.
JSONWriter	value(boolean b) Append either the value true or the value false.
JSONWriter	value(double d) Append a double value.
JSONWriter	value(long l) Append a long value.
JSONWriter	value(Object object) Append an object value.
static String	valueToString(Object value) Make a JSON text of an Object value.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

mode

protected char mode

The current mode. Values: 'a' (array), 'd' (done), 'i' (initial), 'k' (key), 'o' (object).

writer

protected Appendable writer

The writer that will receive the output.

Constructor Detail

JSONWriter

public JSONWriter(Appendable w)

Make a fresh JSONWriter. It can be used to build one JSON text.

Parameters:

w - an appendable object

Method Detail

array

public JSONWriter array()
                 throws JSONException

Begin appending a new array. All values until the balancing endArray will be appended to this array. The endArray method must be called to mark the array's end.

Returns:

this

Throws:

JSONException - If the nesting is too deep, or if the object is started in the wrong place (for example as a key or after the end of the outermost array or object).

endArray

public JSONWriter endArray()
                    throws JSONException

End an array. This method most be called to balance calls to array.

Returns:

this

Throws:

JSONException - If incorrectly nested.

endObject

public JSONWriter endObject()
                     throws JSONException

End an object. This method most be called to balance calls to object.

Returns:

this

Throws:

JSONException - If incorrectly nested.

key

public JSONWriter key(String string)
               throws JSONException

Append a key. The key will be associated with the next value. In an object, every value must be preceded by a key.

Parameters:

string - A key string.

Returns:

this

Throws:

JSONException - If the key is out of place. For example, keys do not belong in arrays or if the key is null.

object

public JSONWriter object()
                  throws JSONException

Begin appending a new object. All keys and values until the balancing endObject will be appended to this object. The endObject method must be called to mark the object's end.

Returns:

this

Throws:

JSONException - If the nesting is too deep, or if the object is started in the wrong place (for example as a key or after the end of the outermost array or object).

valueToString

public static String valueToString(Object value)
                            throws JSONException

Make a JSON text of an Object value. If the object has an value.toJSONString() method, then that method will be used to produce the JSON text. The method is required to produce a strictly conforming text. If the object does not contain a toJSONString method (which is the most common case), then a text will be produced by other means. If the value is an array or Collection, then a JSONArray will be made from it and its toJSONString method will be called. If the value is a MAP, then a JSONObject will be made from it and its toJSONString method will be called. Otherwise, the value's toString method will be called, and the result will be quoted.

Warning: This method assumes that the data structure is acyclical.

Parameters:

value - The value to be serialized.

Returns:

a printable, displayable, transmittable representation of the object, beginning with { (left brace) and ending with } (right brace).

Throws:

JSONException - If the value is or contains an invalid number.

value

public JSONWriter value(boolean b)
                 throws JSONException

Append either the value true or the value false.

Parameters:

b - A boolean.

Returns:

this

Throws:

JSONException - if a called function has an error

value

public JSONWriter value(double d)
                 throws JSONException

Append a double value.

Parameters:

d - A double.

Returns:

this

Throws:

JSONException - If the number is not finite.

value

public JSONWriter value(long l)
                 throws JSONException

Append a long value.

Parameters:

l - A long.

Returns:

this

Throws:

JSONException - if a called function has an error

value

public JSONWriter value(Object object)
                 throws JSONException

Append an object value.

Parameters:

object - The object to append. It can be null, or a Boolean, Number, String, JSONObject, or JSONArray, or an object that implements JSONString.

Returns:

this

Throws:

JSONException - If the value is out of sequence.