std.json

JavaScript Object Notation

License:

Boost License 1.0.

Authors:

Jeremie Pelletier, David Herberth

References

http://json.org/, http://seriot.ch/parsing_json.html

Source

std/json.d

Examples:

import std.conv : to;

// parse a file or string of json into a usable structure
string s = `{ "language": "D", "rating": 3.5, "code": "42" }`;
JSONValue j = parseJSON(s);
// j and j["language"] return JSONValue,
// j["language"].str returns a string
writeln(j["language"].str); // "D"
writeln(j["rating"].floating); // 3.5

// check a type
long x;
if (const(JSONValue)* code = "code" in j)
{
    if (code.type() == JSONType.integer)
        x = code.integer;
    else
        x = to!int(code.str);
}

// create a json struct
JSONValue jj = [ "language": "D" ];
// rating doesnt exist yet, so use .object to assign
jj.object["rating"] = JSONValue(3.5);
// create an array to assign to list
jj.object["list"] = JSONValue( ["a", "b", "c"] );
// list already exists, so .object optional
jj["list"].array ~= JSONValue("D");

string jjStr = `{"language":"D","list":["a","b","c","D"],"rating":3.5}`;
writeln(jj.toString); // jjStr

enum JSONFloatLiteral: string;

String literals used to represent special float values within JSON strings.

nan

string representation of floating-point NaN

inf

string representation of floating-point Infinity

negativeInf

string representation of floating-point negative Infinity

enum JSONOptions: int;

Flags that control how json is encoded and parsed.

none

standard parsing

specialFloatLiterals

encode NaN and Inf float values as strings

escapeNonAsciiChars

encode non ascii characters with an unicode escape sequence

doNotEscapeSlashes

do not escape slashes ('/')

strictParsing

Strictly follow RFC-8259 grammar when parsing

enum JSONType: byte;

JSON type enumeration

null_

string

integer

uinteger

float_

array

object

true_

false_

Indicates the type of a JSONValue.

struct JSONValue;

JSON value node

const pure nothrow @nogc @property @safe JSONType type();

Returns the JSONType of the value stored in this structure.

Examples:

string s = "{ \"language\": \"D\" }";
JSONValue j = parseJSON(s);
writeln(j.type); // JSONType.object
writeln(j["language"].type); // JSONType.string

const pure @property @trusted string str();

pure nothrow @nogc @property @safe string str(string v);

Value getter/setter for JSONType.string.

Throws:

JSONException for read access if type is not JSONType.string.

Examples:

JSONValue j = [ "language": "D" ];

// get value
writeln(j["language"].str); // "D"

// change existing key to new string
j["language"].str = "Perl";
writeln(j["language"].str); // "Perl"

const pure @property @safe long integer();

pure nothrow @nogc @property @safe long integer(long v);

Value getter/setter for JSONType.integer.

Throws:

JSONException for read access if type is not JSONType.integer.

const pure @property @safe ulong uinteger();

pure nothrow @nogc @property @safe ulong uinteger(ulong v);

Value getter/setter for JSONType.uinteger.

Throws:

JSONException for read access if type is not JSONType.uinteger.

const pure @property @safe double floating();

pure nothrow @nogc @property @safe double floating(double v);

Value getter/setter for JSONType.float_. Note that despite the name, this is a 64-bit double, not a 32-bit float.

Throws:

JSONException for read access if type is not JSONType.float_.

const pure @property @safe bool boolean();

pure nothrow @nogc @property @safe bool boolean(bool v);

Value getter/setter for boolean stored in JSON.

Throws:

JSONException for read access if this.type is not JSONType.true_ or JSONType.false_.

Examples:

JSONValue j = true;
writeln(j.boolean); // true

j.boolean = false;
writeln(j.boolean); // false

j.integer = 12;
import std.exception : assertThrown;
assertThrown!JSONException(j.boolean);

inout pure @property ref @system inout(JSONValue[string]) object();

pure nothrow @nogc @property @safe JSONValue[string] object(JSONValue[string] v);

Value getter/setter for JSONType.object.

Throws:

JSONException for read access if type is not JSONType.object.

Note

this is @system because of the following pattern:

auto a = &(json.object());
json.uinteger = 0;        // overwrite AA pointer
(*a)["hello"] = "world";  // segmentation fault

inout pure @property @trusted inout(JSONValue[string]) objectNoRef();

Value getter for JSONType.object. Unlike object, this retrieves the object by value and can be used in @safe code.

A caveat is that, if the returned value is null, modifications will not be visible:

JSONValue json;
json.object = null;
json.objectNoRef["hello"] = JSONValue("world");
assert("hello" !in json.object);

Throws:

JSONException for read access if type is not JSONType.object.

inout pure @property ref @system inout(JSONValue[]) array();

pure nothrow @nogc @property @safe JSONValue[] array(JSONValue[] v);

Value getter/setter for JSONType.array.

Throws:

JSONException for read access if type is not JSONType.array.

Note

this is @system because of the following pattern:

auto a = &(json.array());
json.uinteger = 0;  // overwrite array pointer
(*a)[0] = "world";  // segmentation fault

inout pure @property @trusted inout(JSONValue[]) arrayNoRef();

Value getter for JSONType.array. Unlike array, this retrieves the array by value and can be used in @safe code.

A caveat is that, if you append to the returned array, the new values aren't visible in the

JSONValue

JSONValue json;
json.array = [JSONValue("hello")];
json.arrayNoRef ~= JSONValue("world");
assert(json.array.length == 1);

Throws:

JSONException for read access if type is not JSONType.array.

const pure nothrow @nogc @property @safe bool isNull();

Test whether the type is JSONType.null_

inout const pure @property @safe inout(T) get(T)();

inout pure @property @trusted inout(T) get(T : JSONValue[string])();

Generic type value getter A convenience getter that returns this JSONValue as the specified D type.

Note

only numeric, bool, string, JSONValue[string] and JSONValue[] types are accepted

Throws:

JSONException if T cannot hold the contents of this JSONValue ConvException in case of integer overflow when converting to T

Examples:

import std.exception;
import std.conv;
string s =
`{
    "a": 123,
    "b": 3.1415,
    "c": "text",
    "d": true,
    "e": [1, 2, 3],
    "f": { "a": 1 },
    "g": -45,
    "h": ` ~ ulong.max.to!string ~ `,
 }`;

struct a { }

immutable json = parseJSON(s);
writeln(json["a"].get!double); // 123.0
writeln(json["a"].get!int); // 123
writeln(json["a"].get!uint); // 123
writeln(json["b"].get!double); // 3.1415
assertThrown!JSONException(json["b"].get!int);
writeln(json["c"].get!string); // "text"
writeln(json["d"].get!bool); // true
assertNotThrown(json["e"].get!(JSONValue[]));
assertNotThrown(json["f"].get!(JSONValue[string]));
static assert(!__traits(compiles, json["a"].get!a));
assertThrown!JSONException(json["e"].get!float);
assertThrown!JSONException(json["d"].get!(JSONValue[string]));
assertThrown!JSONException(json["f"].get!(JSONValue[]));
writeln(json["g"].get!int); // -45
assertThrown!ConvException(json["g"].get!uint);
writeln(json["h"].get!ulong); // ulong.max
assertThrown!ConvException(json["h"].get!uint);
assertNotThrown(json["h"].get!float);

this(T)(T arg)
Constraints: if (!isStaticArray!T);

this(T)(ref T arg)
Constraints: if (isStaticArray!T);

inout this(T : JSONValue)(inout T arg);

Constructor for JSONValue. If arg is a JSONValue its value and type will be copied to the new JSONValue. Note that this is a shallow copy: if type is JSONType.object or JSONType.array then only the reference to the data will be copied. Otherwise, arg must be implicitly convertible to one of the following types: typeof(null), string, ulong, long, double, an associative array V[K] for any V and K i.e. a JSON object, any array or bool. The type will be set accordingly.

Examples:

JSONValue j = JSONValue( "a string" );
j = JSONValue(42);

j = JSONValue( [1, 2, 3] );
writeln(j.type); // JSONType.array

j = JSONValue( ["language": "D"] );
writeln(j.type); // JSONType.object

inout pure ref @safe inout(JSONValue) opIndex(size_t i);

Array syntax for json arrays.

Throws:

JSONException if type is not JSONType.array.

Examples:

JSONValue j = JSONValue( [42, 43, 44] );
writeln(j[0].integer); // 42
writeln(j[1].integer); // 43

inout pure ref @safe inout(JSONValue) opIndex(string k);

Hash syntax for json objects.

Throws:

JSONException if type is not JSONType.object.

Examples:

JSONValue j = JSONValue( ["language": "D"] );
writeln(j["language"].str); // "D"

void opIndexAssign(T)(auto ref T value, string key);

Operator sets value for element of JSON object by key.

If JSON value is null, then operator initializes it with object and then sets value for it.

Throws:

JSONException if type is not JSONType.object or JSONType.null_.

Examples:

JSONValue j = JSONValue( ["language": "D"] );
j["language"].str = "Perl";
writeln(j["language"].str); // "Perl"

const @safe auto opBinaryRight(string op : "in")(string k);

Support for the in operator.

Tests wether a key can be found in an object.

Returns:

when found, the const(JSONValue)* that matches to the key, otherwise null.

Throws:

JSONException if the right hand side argument JSONType is not object.

Examples:

JSONValue j = [ "language": "D", "author": "walter" ];
string a = ("author" in j).str;

@system int opApply(scope int delegate(size_t index, ref JSONValue) dg);

Implements the foreach opApply interface for json arrays.

@system int opApply(scope int delegate(string key, ref JSONValue) dg);

Implements the foreach opApply interface for json objects.

const @safe string toString(in JSONOptions options = JSONOptions.none);

Implicitly calls toJSON on this JSONValue.

options can be used to tweak the conversion behavior.

const void toString(Out)(Out sink, in JSONOptions options = JSONOptions.none);

const @safe string toPrettyString(in JSONOptions options = JSONOptions.none);

Implicitly calls toJSON on this JSONValue, like toString, but also passes true as pretty argument.

options can be used to tweak the conversion behavior

const void toPrettyString(Out)(Out sink, in JSONOptions options = JSONOptions.none);

JSONValue parseJSON(T)(T json, int maxDepth = -1, JSONOptions options = JSONOptions.none)
Constraints: if (isInputRange!T && !isInfinite!T && isSomeChar!(ElementEncodingType!T));

Parses a serialized string and returns a tree of JSON values.

Throws:

JSONException if string does not follow the JSON grammar or the depth exceeds the max depth, ConvException if a number in the input cannot be represented by a native D type.

Parameters:

T json	json-formatted string to parse
int maxDepth	maximum depth of nesting allowed, -1 disables depth checking
JSONOptions options	enable decoding string representations of NaN/Inf as float values

JSONValue parseJSON(T)(T json, JSONOptions options)
Constraints: if (isInputRange!T && !isInfinite!T && isSomeChar!(ElementEncodingType!T));

Parses a serialized string and returns a tree of JSON values.

Throws:

JSONException if the depth exceeds the max depth.

Parameters:

T json	json-formatted string to parse
JSONOptions options	enable decoding string representations of NaN/Inf as float values

@safe string toJSON(ref const JSONValue root, in bool pretty = false, in JSONOptions options = JSONOptions.none);

Takes a tree of JSON values and returns the serialized string.

Any Object types will be serialized in a key-sorted order.

If pretty is false no whitespaces are generated. If pretty is true serialized string is formatted to be human-readable. Set the JSONOptions.specialFloatLiterals flag is set in options to encode NaN/Infinity as strings.

void toJSON(Out)(auto ref Out json, ref const JSONValue root, in bool pretty = false, in JSONOptions options = JSONOptions.none)
Constraints: if (isOutputRange!(Out, char));

class JSONException: object.Exception;

Exception thrown on JSON errors