JSONObject

public class JSONObject extends Object

A modifiable set of name/value mappings. Names are unique, non-null strings. Values may be any mix of JSONObjects, JSONArrays, Strings, Booleans, Integers, Longs, Doubles or NULL. Values may not be null, NaNs, infinities, or of any type not listed here.

This class can coerce values to another type when requested.

  • When the requested type is a boolean, strings will be coerced using a case-insensitive comparison to "true" and "false".
  • When the requested type is a double, other Number types will be coerced using doubleValue. Strings that can be coerced using valueOf(String) will be.
  • When the requested type is an int, other Number types will be coerced using intValue. Strings that can be coerced using valueOf(String) will be, and then cast to int.
  • When the requested type is a long, other Number types will be coerced using longValue. Strings that can be coerced using valueOf(String) will be, and then cast to long. This two-step conversion is lossy for very large values. For example, the string "9223372036854775806" yields the long 9223372036854775807.
  • When the requested type is a String, other non-null values will be coerced using valueOf(Object). Although null cannot be coerced, the sentinel value NULL is coerced to the string "null".

This class can look up both mandatory and optional values:

  • Use getType() to retrieve a mandatory value. This fails with a JSONException if the requested name has no value or if the value cannot be coerced to the requested type.
  • Use optType() to retrieve an optional value. This returns a system- or user-supplied default if the requested name has no value or if the value cannot be coerced to the requested type.

Warning: this class represents null in two incompatible ways: the standard Java null reference, and the sentinel value NULL. In particular, calling put(name, null) removes the named entry from the object but put(name, JSONObject.NULL) stores an entry whose value is JSONObject.NULL.

Instances of this class are not thread safe. Although this class is nonfinal, it was not designed for inheritance and should not be subclassed. In particular, self-use by overrideable methods is not specified. See Effective Java Item 17, "Design and Document or inheritance or else prohibit it" for further information.

Field Summary

public static final Object NULL A sentinel value used to explicitly define a name with no value.

Public Constructor Summary

JSONObject()
Creates a JSONObject with no name/value mappings.
JSONObject(Map copyFrom)
Creates a new JSONObject by copying all name/value mappings from the given map.
JSONObject(JSONTokener readFrom)
Creates a new JSONObject with name/value mappings from the next object in the tokener.
JSONObject(String json)
Creates a new JSONObject with name/value mappings from the JSON string.
JSONObject(JSONObject copyFrom, String[] names)
Creates a new JSONObject by copying mappings for the listed names from the given object.

Public Method Summary

JSONObject
accumulate(String name, Object value)
Appends value to the array already mapped to name.
Object
get(String name)
Returns the value mapped by name, or throws if no such mapping exists.
boolean
getBoolean(String name)
Returns the value mapped by name if it exists and is a boolean or can be coerced to a boolean, or throws otherwise.
double
getDouble(String name)
Returns the value mapped by name if it exists and is a double or can be coerced to a double, or throws otherwise.
int
getInt(String name)
Returns the value mapped by name if it exists and is an int or can be coerced to an int, or throws otherwise.
JSONArray
getJSONArray(String name)
Returns the value mapped by name if it exists and is a JSONArray, or throws otherwise.
JSONObject
getJSONObject(String name)
Returns the value mapped by name if it exists and is a JSONObject, or throws otherwise.
long
getLong(String name)
Returns the value mapped by name if it exists and is a long or can be coerced to a long, or throws otherwise.
String
getString(String name)
Returns the value mapped by name if it exists, coercing it if necessary, or throws if no such mapping exists.
boolean
has(String name)
Returns true if this object has a mapping for name.
boolean
isNull(String name)
Returns true if this object has no mapping for name or if it has a mapping whose value is NULL.
Iterator<String>
keys()
Returns an iterator of the String names in this object.
int
length()
Returns the number of name/value mappings in this object.
JSONArray
names()
Returns an array containing the string names in this object.
static String
numberToString(Number number)
Encodes the number as a JSON string.
Object
opt(String name)
Returns the value mapped by name, or null if no such mapping exists.
boolean
optBoolean(String name, boolean fallback)
Returns the value mapped by name if it exists and is a boolean or can be coerced to a boolean, or fallback otherwise.
boolean
optBoolean(String name)
Returns the value mapped by name if it exists and is a boolean or can be coerced to a boolean, or false otherwise.
double
optDouble(String name, double fallback)
Returns the value mapped by name if it exists and is a double or can be coerced to a double, or fallback otherwise.
double
optDouble(String name)
Returns the value mapped by name if it exists and is a double or can be coerced to a double, or NaN otherwise.
int
optInt(String name, int fallback)
Returns the value mapped by name if it exists and is an int or can be coerced to an int, or fallback otherwise.
int
optInt(String name)
Returns the value mapped by name if it exists and is an int or can be coerced to an int, or 0 otherwise.
JSONArray
optJSONArray(String name)
Returns the value mapped by name if it exists and is a JSONArray, or null otherwise.
JSONObject
optJSONObject(String name)
Returns the value mapped by name if it exists and is a JSONObject, or null otherwise.
long
optLong(String name)
Returns the value mapped by name if it exists and is a long or can be coerced to a long, or 0 otherwise.
long
optLong(String name, long fallback)
Returns the value mapped by name if it exists and is a long or can be coerced to a long, or fallback otherwise.
String
optString(String name, String fallback)
Returns the value mapped by name if it exists, coercing it if necessary, or fallback if no such mapping exists.
String
optString(String name)
Returns the value mapped by name if it exists, coercing it if necessary, or the empty string if no such mapping exists.
JSONObject
put(String name, double value)
Maps name to value, clobbering any existing name/value mapping with the same name.
JSONObject
put(String name, boolean value)
Maps name to value, clobbering any existing name/value mapping with the same name.
JSONObject
put(String name, int value)
Maps name to value, clobbering any existing name/value mapping with the same name.
JSONObject
put(String name, long value)
Maps name to value, clobbering any existing name/value mapping with the same name.
JSONObject
put(String name, Object value)
Maps name to value, clobbering any existing name/value mapping with the same name.
JSONObject
putOpt(String name, Object value)
Equivalent to put(name, value) when both parameters are non-null; does nothing otherwise.
static String
quote(String data)
Encodes data as a JSON string.
Object
remove(String name)
Removes the named mapping if it exists; does nothing otherwise.
JSONArray
toJSONArray(JSONArray names)
Returns an array with the values corresponding to names.
String
toString()
Encodes this object as a compact JSON string, such as:
{"query":"Pizza","locations":[94043,90210]}
String
toString(int indentSpaces)
Encodes this object as a human readable JSON string for debugging, such as:
 {
     "query": "Pizza",
     "locations": [
         94043,
         90210
     ]
 }
static Object
wrap(Object o)
Wraps the given object if necessary.

Inherited Method Summary

Fields

public static final Object NULL

A sentinel value used to explicitly define a name with no value. Unlike null, names with this value:

This value violates the general contract of equals(Object) by returning true when compared to null. Its toString() method returns "null".

Public Constructors

public JSONObject ()

Creates a JSONObject with no name/value mappings.

public JSONObject (Map copyFrom)

Creates a new JSONObject by copying all name/value mappings from the given map.

Parameters
copyFrom a map whose keys are of type String and whose values are of supported types.
Throws
NullPointerException if any of the map's keys are null.

public JSONObject (JSONTokener readFrom)

Creates a new JSONObject with name/value mappings from the next object in the tokener.

Parameters
readFrom a tokener whose nextValue() method will yield a JSONObject.
Throws
JSONException if the parse fails or doesn't yield a JSONObject.

public JSONObject (String json)

Creates a new JSONObject with name/value mappings from the JSON string.

Parameters
json a JSON-encoded string containing an object.
Throws
JSONException if the parse fails or doesn't yield a JSONObject.

public JSONObject (JSONObject copyFrom, String[] names)

Creates a new JSONObject by copying mappings for the listed names from the given object. Names that aren't present in copyFrom will be skipped.

Parameters
copyFrom
names
Throws
JSONException

Public Methods

public JSONObject accumulate (String name, Object value)

Appends value to the array already mapped to name. If this object has no mapping for name, this inserts a new mapping. If the mapping exists but its value is not an array, the existing and new values are inserted in order into a new array which is itself mapped to name. In aggregate, this allows values to be added to a mapping one at a time.

Note that append(String, Object) provides better semantics. In particular, the mapping for name will always be a JSONArray. Using accumulate will result in either a JSONArray or a mapping whose type is the type of value depending on the number of calls to it.

Parameters
name
value a JSONObject, JSONArray, String, Boolean, Integer, Long, Double, NULL or null. May not be NaNs or infinities.
Throws
JSONException

public Object get (String name)

Returns the value mapped by name, or throws if no such mapping exists.

Parameters
name
Throws
JSONException if no such mapping exists.

public boolean getBoolean (String name)

Returns the value mapped by name if it exists and is a boolean or can be coerced to a boolean, or throws otherwise.

Parameters
name
Throws
JSONException if the mapping doesn't exist or cannot be coerced to a boolean.

public double getDouble (String name)

Returns the value mapped by name if it exists and is a double or can be coerced to a double, or throws otherwise.

Parameters
name
Throws
JSONException if the mapping doesn't exist or cannot be coerced to a double.

public int getInt (String name)

Returns the value mapped by name if it exists and is an int or can be coerced to an int, or throws otherwise.

Parameters
name
Throws
JSONException if the mapping doesn't exist or cannot be coerced to an int.

public JSONArray getJSONArray (String name)

Returns the value mapped by name if it exists and is a JSONArray, or throws otherwise.

Parameters
name
Throws
JSONException if the mapping doesn't exist or is not a JSONArray.

public JSONObject getJSONObject (String name)

Returns the value mapped by name if it exists and is a JSONObject, or throws otherwise.

Parameters
name
Throws
JSONException if the mapping doesn't exist or is not a JSONObject.

public long getLong (String name)

Returns the value mapped by name if it exists and is a long or can be coerced to a long, or throws otherwise. Note that JSON represents numbers as doubles, so this is lossy; use strings to transfer numbers via JSON.

Parameters
name
Throws
JSONException if the mapping doesn't exist or cannot be coerced to a long.

public String getString (String name)

Returns the value mapped by name if it exists, coercing it if necessary, or throws if no such mapping exists.

Parameters
name
Throws
JSONException if no such mapping exists.

public boolean has (String name)

Returns true if this object has a mapping for name. The mapping may be NULL.

Parameters
name

public boolean isNull (String name)

Returns true if this object has no mapping for name or if it has a mapping whose value is NULL.

Parameters
name

public Iterator<String> keys ()

Returns an iterator of the String names in this object. The returned iterator supports remove, which will remove the corresponding mapping from this object. If this object is modified after the iterator is returned, the iterator's behavior is undefined. The order of the keys is undefined.

public int length ()

Returns the number of name/value mappings in this object.

public JSONArray names ()

Returns an array containing the string names in this object. This method returns null if this object contains no mappings.

public static String numberToString (Number number)

Encodes the number as a JSON string.

Parameters
number a finite value. May not be NaNs or infinities.
Throws
JSONException

public Object opt (String name)

Returns the value mapped by name, or null if no such mapping exists.

Parameters
name

public boolean optBoolean (String name, boolean fallback)

Returns the value mapped by name if it exists and is a boolean or can be coerced to a boolean, or fallback otherwise.

Parameters
name
fallback

public boolean optBoolean (String name)

Returns the value mapped by name if it exists and is a boolean or can be coerced to a boolean, or false otherwise.

Parameters
name

public double optDouble (String name, double fallback)

Returns the value mapped by name if it exists and is a double or can be coerced to a double, or fallback otherwise.

Parameters
name
fallback

public double optDouble (String name)

Returns the value mapped by name if it exists and is a double or can be coerced to a double, or NaN otherwise.

Parameters
name

public int optInt (String name, int fallback)

Returns the value mapped by name if it exists and is an int or can be coerced to an int, or fallback otherwise.

Parameters
name
fallback

public int optInt (String name)

Returns the value mapped by name if it exists and is an int or can be coerced to an int, or 0 otherwise.

Parameters
name

public JSONArray optJSONArray (String name)

Returns the value mapped by name if it exists and is a JSONArray, or null otherwise.

Parameters
name

public JSONObject optJSONObject (String name)

Returns the value mapped by name if it exists and is a JSONObject, or null otherwise.

Parameters
name

public long optLong (String name)

Returns the value mapped by name if it exists and is a long or can be coerced to a long, or 0 otherwise. Note that JSON represents numbers as doubles, so this is lossy; use strings to transfer numbers via JSON.

Parameters
name

public long optLong (String name, long fallback)

Returns the value mapped by name if it exists and is a long or can be coerced to a long, or fallback otherwise. Note that JSON represents numbers as doubles, so this is lossy; use strings to transfer numbers via JSON.

Parameters
name
fallback

public String optString (String name, String fallback)

Returns the value mapped by name if it exists, coercing it if necessary, or fallback if no such mapping exists.

Parameters
name
fallback

public String optString (String name)

Returns the value mapped by name if it exists, coercing it if necessary, or the empty string if no such mapping exists.

Parameters
name

public JSONObject put (String name, double value)

Maps name to value, clobbering any existing name/value mapping with the same name.

Parameters
name
value a finite value. May not be NaNs or infinities.
Returns
  • this object.
Throws
JSONException

public JSONObject put (String name, boolean value)

Maps name to value, clobbering any existing name/value mapping with the same name.

Parameters
name
value
Returns
  • this object.
Throws
JSONException

public JSONObject put (String name, int value)

Maps name to value, clobbering any existing name/value mapping with the same name.

Parameters
name
value
Returns
  • this object.
Throws
JSONException

public JSONObject put (String name, long value)

Maps name to value, clobbering any existing name/value mapping with the same name.

Parameters
name
value
Returns
  • this object.
Throws
JSONException

public JSONObject put (String name, Object value)

Maps name to value, clobbering any existing name/value mapping with the same name. If the value is null, any existing mapping for name is removed.

Parameters
name
value a JSONObject, JSONArray, String, Boolean, Integer, Long, Double, NULL, or null. May not be NaNs or infinities.
Returns
  • this object.
Throws
JSONException

public JSONObject putOpt (String name, Object value)

Equivalent to put(name, value) when both parameters are non-null; does nothing otherwise.

Parameters
name
value
Throws
JSONException

public static String quote (String data)

Encodes data as a JSON string. This applies quotes and any necessary character escaping.

Parameters
data the string to encode. Null will be interpreted as an empty string.

public Object remove (String name)

Removes the named mapping if it exists; does nothing otherwise.

Parameters
name
Returns
  • the value previously mapped by name, or null if there was no such mapping.

public JSONArray toJSONArray (JSONArray names)

Returns an array with the values corresponding to names. The array contains null for names that aren't mapped. This method returns null if names is either null or empty.

Parameters
names
Throws
JSONException

public String toString ()

Encodes this object as a compact JSON string, such as:

{"query":"Pizza","locations":[94043,90210]}

public String toString (int indentSpaces)

Encodes this object as a human readable JSON string for debugging, such as:

 {
     "query": "Pizza",
     "locations": [
         94043,
         90210
     ]
 }

Parameters
indentSpaces the number of spaces to indent for each level of nesting.
Throws
JSONException

public static Object wrap (Object o)

Wraps the given object if necessary.

If the object is null or , returns NULL. If the object is a JSONArray or JSONObject, no wrapping is necessary. If the object is NULL, no wrapping is necessary. If the object is an array or Collection, returns an equivalent JSONArray. If the object is a Map, returns an equivalent JSONObject. If the object is a primitive wrapper type or String, returns the object. Otherwise if the object is from a java package, returns the result of toString. If wrapping fails, returns null.

Parameters
o