org.json
Class JSONObject

java.lang.Object
  org.json.JSONObject

public class JSONObject
extends java.lang.Object

A JSONObject is an unordered collection of name/value pairs. Its external form is a string wrapped in curly braces with colons between the names and values, and commas between the values and names. The internal form is an object having get() and opt() methods for accessing the values by name, and put() methods for adding or replacing values by name. The values can be any of these types: Boolean, JSONArray, JSONObject, Number, String, or the JSONObject.NULL object.

The constructor can convert an external form string into an internal form Java object. The toString() method creates an external form string.

A get() method returns a value if one can be found, and throws an exception if one cannot be found. An opt() method returns a default value instead of throwing an exception, and so is useful for obtaining optional values.

The generic get() and opt() methods return an object, which you can cast or query for type. There are also typed get() and opt() methods that do type checking and type coersion for you.

The texts produced by the toString() methods are very strict. The constructors are more forgiving in the texts they will accept:

• An extra , (comma) may appear just before the closing brace.
• Strings may be quoted with ' (single quote).
• Strings do not need to be quoted at all if they do not begin with a quote or single quote, and if they do not contain leading or trailing spaces, and if they do not contain any of these characters: { } [ ] / \ : , = ; # and if they do not look like numbers and if they are not the reserved words true, false, or null.
• Keys can be followed by = or => as well as by :
• Values can be followed by ; as well as by ,
• Numbers may have the 0- (octal) or 0x- (hex) prefix.
• Line comments can begin with #

Version:

1

Author:

JSON.org

Field Summary

static java.lang.Object

NULL It is sometimes more convenient and less ambiguous to have a NULL object than to use Java's null value.

Constructor Summary

JSONObject()
Construct an empty JSONObject.

JSONObject(JSONTokener x)
Construct a JSONObject from a JSONTokener.

JSONObject(java.util.Map map)
Construct a JSONObject from a Map.

JSONObject(java.lang.String string)
Construct a JSONObject from a string.

Method Summary

JSONObject	accumulate(java.lang.String key, java.lang.Object value) Accumulate values under a key.
java.lang.Object	get(java.lang.String key) Get the value object associated with a key.
boolean	getBoolean(java.lang.String key) Get the boolean value associated with a key.
double	getDouble(java.lang.String key) Get the double value associated with a key.
int	getInt(java.lang.String key) Get the int value associated with a key.
JSONArray	getJSONArray(java.lang.String key) Get the JSONArray value associated with a key.
JSONObject	getJSONObject(java.lang.String key) Get the JSONObject value associated with a key.
java.lang.String	getString(java.lang.String key) Get the string associated with a key.
boolean	has(java.lang.String key) Determine if the JSONObject contains a specific key.
boolean	isNull(java.lang.String key) Determine if the value associated with the key is null or if there is no value.
java.util.Iterator	keys() Get an enumeration of the keys of the JSONObject.
int	length() Get the number of keys stored in the JSONObject.
JSONArray	names() Produce a JSONArray containing the names of the elements of this JSONObject.
static java.lang.String	numberToString(java.lang.Number n) Produce a string from a number.
java.lang.Object	opt(java.lang.String key) Get an optional value associated with a key.
boolean	optBoolean(java.lang.String key) Get an optional boolean associated with a key.
boolean	optBoolean(java.lang.String key, boolean defaultValue) Get an optional boolean associated with a key.
double	optDouble(java.lang.String key) Get an optional double associated with a key, or NaN if there is no such key or if its value is not a number.
double	optDouble(java.lang.String key, double defaultValue) Get an optional double associated with a key, or the defaultValue if there is no such key or if its value is not a number.
int	optInt(java.lang.String key) Get an optional int value associated with a key, or zero if there is no such key or if the value is not a number.
int	optInt(java.lang.String key, int defaultValue) Get an optional int value associated with a key, or the default if there is no such key or if the value is not a number.
JSONArray	optJSONArray(java.lang.String key) Get an optional JSONArray associated with a key.
JSONObject	optJSONObject(java.lang.String key) Get an optional JSONObject associated with a key.
java.lang.String	optString(java.lang.String key) Get an optional string associated with a key.
java.lang.String	optString(java.lang.String key, java.lang.String defaultValue) Get an optional string associated with a key.
JSONObject	put(java.lang.String key, boolean value) Put a key/boolean pair in the JSONObject.
JSONObject	put(java.lang.String key, double value) Put a key/double pair in the JSONObject.
JSONObject	put(java.lang.String key, int value) Put a key/int pair in the JSONObject.
JSONObject	put(java.lang.String key, java.lang.Object value) Put a key/value pair in the JSONObject.
JSONObject	putOpt(java.lang.String key, java.lang.Object value) Put a key/value pair in the JSONObject, but only if the value is non-null.
static java.lang.String	quote(java.lang.String string) Produce a string in double quotes with backslash sequences in all the right places.
java.lang.Object	remove(java.lang.String key) Remove a name and its value, if present.
JSONArray	toJSONArray(JSONArray names) Produce a JSONArray containing the values of the members of this JSONObject.
java.lang.String	toString() Make an JSON external form string of this JSONObject.
java.lang.String	toString(int indentFactor) Make a prettyprinted JSON external form string of this JSONObject.

Methods inherited from class java.lang.Object

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

Field Detail

NULL

public static final java.lang.Object NULL

It is sometimes more convenient and less ambiguous to have a NULL object than to use Java's null value. JSONObject.NULL.equals(null) returns true. JSONObject.NULL.toString() returns "null".

Constructor Detail

JSONObject

public JSONObject()

Construct an empty JSONObject.

JSONObject

public JSONObject(JSONTokener x)
           throws java.text.ParseException

Construct a JSONObject from a JSONTokener.

Parameters:

x - A JSONTokener object containing the source string.

Throws:

java.text.ParseException - if there is a syntax error in the source string.

JSONObject

public JSONObject(java.lang.String string)
           throws java.text.ParseException

Construct a JSONObject from a string.

Parameters:

string - A string beginning with { (left brace) and ending with } (right brace).

Throws:

java.text.ParseException - The string must be properly formatted.

JSONObject

public JSONObject(java.util.Map map)

Construct a JSONObject from a Map.

Parameters:

map - A map object that can be used to initialize the contents of the JSONObject.

Method Detail

accumulate

public JSONObject accumulate(java.lang.String key,
                             java.lang.Object value)
                      throws java.lang.NullPointerException

Accumulate values under a key. It is similar to the put method except that if there is already an object stored under the key then a JSONArray is stored under the key to hold all of the accumulated values. If there is already a JSONArray, then the new value is appended to it. In contrast, the put method replaces the previous value.

Parameters:

key - A key string.

value - An object to be accumulated under the key.

Returns:

this.

Throws:

java.lang.NullPointerException - if the key is null

get

public java.lang.Object get(java.lang.String key)
                     throws java.util.NoSuchElementException

Get the value object associated with a key.

Parameters:

key - A key string.

Returns:

The object associated with the key.

Throws:

java.util.NoSuchElementException - if the key is not found.

getBoolean

public boolean getBoolean(java.lang.String key)
                   throws java.lang.ClassCastException,
                          java.util.NoSuchElementException

Get the boolean value associated with a key.

Parameters:

key - A key string.

Returns:

The truth.

Throws:

java.util.NoSuchElementException - if the key is not found.

java.lang.ClassCastException - if the value is not a Boolean or the String "true" or "false".

getDouble

public double getDouble(java.lang.String key)
                 throws java.util.NoSuchElementException,
                        java.lang.NumberFormatException

Get the double value associated with a key.

Parameters:

key - A key string.

Returns:

The numeric value.

Throws:

java.util.NoSuchElementException - if the key is not found or if the value is a Number object.

java.lang.NumberFormatException - if the value cannot be converted to a number.

getInt

public int getInt(java.lang.String key)
           throws java.util.NoSuchElementException,
                  java.lang.NumberFormatException

Get the int value associated with a key.

Parameters:

key - A key string.

Returns:

The integer value.

Throws:

java.util.NoSuchElementException - if the key is not found

java.lang.NumberFormatException - if the value cannot be converted to a number.

getJSONArray

public JSONArray getJSONArray(java.lang.String key)
                       throws java.util.NoSuchElementException

Get the JSONArray value associated with a key.

Parameters:

key - A key string.

Returns:

A JSONArray which is the value.

Throws:

java.util.NoSuchElementException - if the key is not found or if the value is not a JSONArray.

getJSONObject

public JSONObject getJSONObject(java.lang.String key)
                         throws java.util.NoSuchElementException

Get the JSONObject value associated with a key.

Parameters:

key - A key string.

Returns:

A JSONObject which is the value.

Throws:

java.util.NoSuchElementException - if the key is not found or if the value is not a JSONObject.

getString

public java.lang.String getString(java.lang.String key)
                           throws java.util.NoSuchElementException

Get the string associated with a key.

Parameters:

key - A key string.

Returns:

A string which is the value.

Throws:

java.util.NoSuchElementException - if the key is not found.

has

public boolean has(java.lang.String key)

Determine if the JSONObject contains a specific key.

Parameters:

key - A key string.

Returns:

true if the key exists in the JSONObject.

isNull

public boolean isNull(java.lang.String key)

Determine if the value associated with the key is null or if there is no value.

Parameters:

key - A key string.

Returns:

true if there is no value associated with the key or if the value is the JSONObject.NULL object.

keys

public java.util.Iterator keys()

Get an enumeration of the keys of the JSONObject.

Returns:

An iterator of the keys.

length

public int length()

Get the number of keys stored in the JSONObject.

Returns:

The number of keys in the JSONObject.

names

public JSONArray names()

Produce a JSONArray containing the names of the elements of this JSONObject.

Returns:

A JSONArray containing the key strings, or null if the JSONObject is empty.

numberToString

public static java.lang.String numberToString(java.lang.Number n)
                                       throws java.lang.ArithmeticException

Produce a string from a number.

Parameters:

n - A Number

Returns:

A String.

Throws:

java.lang.ArithmeticException - JSON can only serialize finite numbers.

opt

public java.lang.Object opt(java.lang.String key)
                     throws java.lang.NullPointerException

Get an optional value associated with a key.

Parameters:

key - A key string.

Returns:

An object which is the value, or null if there is no value.

Throws:

java.lang.NullPointerException - The key must not be null.

optBoolean

public boolean optBoolean(java.lang.String key)

Get an optional boolean associated with a key. It returns false if there is no such key, or if the value is not Boolean.TRUE or the String "true".

Parameters:

key - A key string.

Returns:

The truth.

optBoolean

public boolean optBoolean(java.lang.String key,
                          boolean defaultValue)

Get an optional boolean associated with a key. It returns the defaultValue if there is no such key, or if it is not a Boolean or the String "true" or "false" (case insensitive).

Parameters:

key - A key string.

defaultValue - The default.

Returns:

The truth.

optDouble

public double optDouble(java.lang.String key)

Get an optional double associated with a key, or NaN if there is no such key or if its value is not a number. If the value is a string, an attempt will be made to evaluate it as a number.

Parameters:

key - A string which is the key.

Returns:

An object which is the value.

optDouble

public double optDouble(java.lang.String key,
                        double defaultValue)

Get an optional double associated with a key, or the defaultValue if there is no such key or if its value is not a number. If the value is a string, an attempt will be made to evaluate it as a number.

Parameters:

key - A key string.

defaultValue - The default.

Returns:

An object which is the value.

optInt

public int optInt(java.lang.String key)

Get an optional int value associated with a key, or zero if there is no such key or if the value is not a number. If the value is a string, an attempt will be made to evaluate it as a number.

Parameters:

key - A key string.

Returns:

An object which is the value.

optInt

public int optInt(java.lang.String key,
                  int defaultValue)

Get an optional int value associated with a key, or the default if there is no such key or if the value is not a number. If the value is a string, an attempt will be made to evaluate it as a number.

Parameters:

key - A key string.

defaultValue - The default.

Returns:

An object which is the value.

optJSONArray

public JSONArray optJSONArray(java.lang.String key)

Get an optional JSONArray associated with a key. It returns null if there is no such key, or if its value is not a JSONArray.

Parameters:

key - A key string.

Returns:

A JSONArray which is the value.

optJSONObject

public JSONObject optJSONObject(java.lang.String key)

Get an optional JSONObject associated with a key. It returns null if there is no such key, or if its value is not a JSONObject.

Parameters:

key - A key string.

Returns:

A JSONObject which is the value.

optString

public java.lang.String optString(java.lang.String key)

Get an optional string associated with a key. It returns an empty string if there is no such key. If the value is not a string and is not null, then it is coverted to a string.

Parameters:

key - A key string.

Returns:

A string which is the value.

optString

public java.lang.String optString(java.lang.String key,
                                  java.lang.String defaultValue)

Get an optional string associated with a key. It returns the defaultValue if there is no such key.

Parameters:

key - A key string.

defaultValue - The default.

Returns:

A string which is the value.

put

public JSONObject put(java.lang.String key,
                      boolean value)

Put a key/boolean pair in the JSONObject.

Parameters:

key - A key string.

value - A boolean which is the value.

Returns:

this.

put

public JSONObject put(java.lang.String key,
                      double value)

Put a key/double pair in the JSONObject.

Parameters:

key - A key string.

value - A double which is the value.

Returns:

this.

put

public JSONObject put(java.lang.String key,
                      int value)

Put a key/int pair in the JSONObject.

Parameters:

key - A key string.

value - An int which is the value.

Returns:

this.

put

public JSONObject put(java.lang.String key,
                      java.lang.Object value)
               throws java.lang.NullPointerException

Put a key/value pair in the JSONObject. If the value is null, then the key will be removed from the JSONObject if it is present.

Parameters:

key - A key string.

value - An object which is the value. It should be of one of these types: Boolean, Double, Integer, JSONArray, JSONObject, String, or the JSONObject.NULL object.

Returns:

this.

Throws:

java.lang.NullPointerException - The key must be non-null.

putOpt

public JSONObject putOpt(java.lang.String key,
                         java.lang.Object value)
                  throws java.lang.NullPointerException

Put a key/value pair in the JSONObject, but only if the value is non-null.

Parameters:

key - A key string.

value - An object which is the value. It should be of one of these types: Boolean, Double, Integer, JSONArray, JSONObject, String, or the JSONObject.NULL object.

Returns:

this.

Throws:

java.lang.NullPointerException - The key must be non-null.

quote

public static java.lang.String quote(java.lang.String string)

Produce a string in double quotes with backslash sequences in all the right places.

Parameters:

string - A String

Returns:

A String correctly formatted for insertion in a JSON message.

remove

public java.lang.Object remove(java.lang.String key)

Remove a name and its value, if present.

Parameters:

key - The name to be removed.

Returns:

The value that was associated with the name, or null if there was no value.

toJSONArray

public JSONArray toJSONArray(JSONArray names)

Produce a JSONArray containing the values of the members of this JSONObject.

Parameters:

names - A JSONArray containing a list of key strings. This determines the sequence of the values in the result.

Returns:

A JSONArray of values.

toString

public java.lang.String toString()

Make an JSON external form string of this JSONObject. For compactness, no unnecessary whitespace is added.

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

Overrides:

toString in class java.lang.Object

Returns:

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

toString

public java.lang.String toString(int indentFactor)

Make a prettyprinted JSON external form string of this JSONObject.

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

Parameters:

indentFactor - The number of spaces to add to each level of indentation.

Returns:

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