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, {@link org.apache.tapestry5.json.JSONArray}, {@link org.apache.tapestry5.json.JSONLiteral},
JSONObject,
Number,
String, or the
JSONObject.NULL object. A JSONObject constructor can be used to convert an external form JSON text into an internal form whose values can be retrieved with the
get and
opt methods, or to convert values into a JSON text using the
put and
toString methods. 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
put methods adds values to an object. For example,
myString = new JSONObject().put("JSON", "Hello, World!").toString(); produces the string
{"JSON": "Hello, World"}.
The texts produced by the
toString methods strictly conform to the JSON syntax rules. 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
; (semicolon) as well as by , (comma). - Numbers may have the
0- (octal) or 0x- (hex) prefix. - Comments written in the slashshlash, slashstar, and hash conventions will be ignored.
This class, and the other related classes, have been heavily modified from the original source, to fit Tapestry standards and to make use of JDK 1.5 features such as generics. Further, since the interest of Tapestry is primarily constructing JSON (and not parsing it), many of the non-essential methods have been removed (since the original code came with no tests).
Finally, support for the {@link org.apache.tapestry5.json.JSONLiteral} type has been added, which allow the exactoutput to be controlled; useful when a JSONObject is being used as a configuration object, and must contain values that are not simple data, such as an inline function (technically making the result not JSON).
@author JSON.org
@version 2