import "encoding/json"

Overview

Index

Examples

func Compact(dst *bytes.Buffer, src []byte) error

func HTMLEscape(dst *bytes.Buffer, src []byte)

func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error

func Marshal(v interface{}) ([]byte, error)

func MarshalIndent(v interface{}, prefix, indent string) ([]byte, error)

func Unmarshal(data []byte, v interface{}) error

type Decoder

    func NewDecoder(r io.Reader) *Decoder

    func (dec *Decoder) Decode(v interface{}) error

type Encoder

    func NewEncoder(w io.Writer) *Encoder

    func (enc *Encoder) Encode(v interface{}) error

type InvalidUTF8Error

    func (e *InvalidUTF8Error) Error() string

type InvalidUnmarshalError

    func (e *InvalidUnmarshalError) Error() string

type Marshaler

type MarshalerError

    func (e *MarshalerError) Error() string

type RawMessage

    func (m *RawMessage) MarshalJSON() ([]byte, error)

    func (m *RawMessage) UnmarshalJSON(data []byte) error

type SyntaxError

    func (e *SyntaxError) Error() string

type UnmarshalFieldError

    func (e *UnmarshalFieldError) Error() string

type UnmarshalTypeError

    func (e *UnmarshalTypeError) Error() string

type Unmarshaler

type UnsupportedTypeError

    func (e *UnsupportedTypeError) Error() string

type UnsupportedValueError

    func (e *UnsupportedValueError) Error() string

Bugs

Examples

Decoder

Marshal

Unmarshal

Package files

decode.go encode.go indent.go scanner.go stream.go tags.go

func Compact

func Compact(dst *bytes.Buffer, src []byte) error

Compact appends to dst the JSON-encoded src with insignificant space characters elided.

func HTMLEscape

func HTMLEscape(dst *bytes.Buffer, src []byte)

HTMLEscape appends to dst the JSON-encoded src with <, >, and & characters inside string literals changed to \u003c, \u003e, \u0026 so that the JSON will be safe to embed inside HTML <script> tags. For historical reasons, web browsers don't honor standard HTML escaping within <script> tags, so an alternative JSON encoding must be used.

func Indent

func Indent(dst *bytes.Buffer, src []byte, prefix, indent string) error

Indent appends to dst an indented form of the JSON-encoded src. Each element in a JSON object or array begins on a new, indented line beginning with prefix followed by one or more copies of indent according to the indentation nesting. The data appended to dst has no trailing newline, to make it easier to embed inside other formatted JSON data.

func Marshal

func Marshal(v interface{}) ([]byte, error)

Marshal returns the JSON encoding of v.

Marshal traverses the value v recursively. If an encountered value implements the Marshaler interface and is not a nil pointer, Marshal calls its MarshalJSON method to produce JSON. The nil pointer exception is not strictly necessary but mimics a similar, necessary exception in the behavior of UnmarshalJSON.

Otherwise, Marshal uses the following type-dependent default encodings:

Boolean values encode as JSON booleans.

Floating point and integer values encode as JSON numbers.

String values encode as JSON strings, with each invalid UTF-8 sequence replaced by the encoding of the Unicode replacement character U+FFFD. The angle brackets "<" and ">" are escaped to "\u003c" and "\u003e" to keep some browsers from misinterpreting JSON output as HTML.

Array and slice values encode as JSON arrays, except that []byte encodes as a base64-encoded string, and a nil slice encodes as the null JSON object.

Struct values encode as JSON objects. Each exported struct field becomes a member of the object unless

- the field's tag is "-", or
- the field is empty and its tag specifies the "omitempty" option.

The empty values are false, 0, any nil pointer or interface value, and any array, slice, map, or string of length zero. The object's default key string is the struct field name but can be specified in the struct field's tag value. The "json" key in struct field's tag value is the key name, followed by an optional comma and options. Examples:

// Field is ignored by this package.
Field int `json:"-"`

// Field appears in JSON as key "myName".
Field int `json:"myName"`

// Field appears in JSON as key "myName" and
// the field is omitted from the object if its value is empty,
// as defined above.
Field int `json:"myName,omitempty"`

// Field appears in JSON as key "Field" (the default), but
// the field is skipped if empty.
// Note the leading comma.
Field int `json:",omitempty"`

The "string" option signals that a field is stored as JSON inside a JSON-encoded string. This extra level of encoding is sometimes used when communicating with JavaScript programs:

Int64String int64 `json:",string"`

The key name will be used if it's a non-empty string consisting of only Unicode letters, digits, dollar signs, percent signs, hyphens, underscores and slashes.

Map values encode as JSON objects. The map's key type must be string; the object keys are used directly as map keys.

Pointer values encode as the value pointed to. A nil pointer encodes as the null JSON object.

Interface values encode as the value contained in the interface. A nil interface value encodes as the null JSON object.

Channel, complex, and function values cannot be encoded in JSON. Attempting to encode such a value causes Marshal to return an InvalidTypeError.

JSON cannot represent cyclic data structures and Marshal does not handle them. Passing cyclic structures to Marshal will result in an infinite recursion.

type ColorGroup struct {
    ID     int
    Name   string
    Colors []string
}
group := ColorGroup{
    ID:     1,
    Name:   "Reds",
    Colors: []string{"Crimson", "Red", "Ruby", "Maroon"},
}
b, err := json.Marshal(group)
if err != nil {
    fmt.Println("error:", err)
}
os.Stdout.Write(b)

{"ID":1,"Name":"Reds","Colors":["Crimson","Red","Ruby","Maroon"]}

func MarshalIndent

func MarshalIndent(v interface{}, prefix, indent string) ([]byte, error)

MarshalIndent is like Marshal but applies Indent to format the output.

func Unmarshal

func Unmarshal(data []byte, v interface{}) error

Unmarshal parses the JSON-encoded data and stores the result in the value pointed to by v.

Unmarshal uses the inverse of the encodings that Marshal uses, allocating maps, slices, and pointers as necessary, with the following additional rules:

To unmarshal JSON into a pointer, Unmarshal first handles the case of the JSON being the JSON literal null. In that case, Unmarshal sets the pointer to nil. Otherwise, Unmarshal unmarshals the JSON into the value pointed at by the pointer. If the pointer is nil, Unmarshal allocates a new value for it to point to.

To unmarshal JSON into an interface value, Unmarshal unmarshals the JSON into the concrete value contained in the interface value. If the interface value is nil, that is, has no concrete value stored in it, Unmarshal stores one of these in the interface value:

bool, for JSON booleans
float64, for JSON numbers
string, for JSON strings
[]interface{}, for JSON arrays
map[string]interface{}, for JSON objects
nil for JSON null

If a JSON value is not appropriate for a given target type, or if a JSON number overflows the target type, Unmarshal skips that field and completes the unmarshalling as best it can. If no more serious errors are encountered, Unmarshal returns an UnmarshalTypeError describing the earliest such error.

var jsonBlob = []byte(`[
    {"Name": "Platypus", "Order": "Monotremata"},
    {"Name": "Quoll",    "Order": "Dasyuromorphia"}
]`)
type Animal struct {
    Name  string
    Order string
}
var animals []Animal
err := json.Unmarshal(jsonBlob, &animals)
if err != nil {
    fmt.Println("error:", err)
}
fmt.Printf("%+v", animals)

[{Name:Platypus Order:Monotremata} {Name:Quoll Order:Dasyuromorphia}]

type Decoder

type Decoder struct {
    // contains filtered or unexported fields
}

A Decoder reads and decodes JSON objects from an input stream.

const jsonStream = `
    {"Name": "Ed", "Text": "Knock knock."}
    {"Name": "Sam", "Text": "Who's there?"}
    {"Name": "Ed", "Text": "Go fmt."}
    {"Name": "Sam", "Text": "Go fmt who?"}
    {"Name": "Ed", "Text": "Go fmt yourself!"}
`
type Message struct {
    Name, Text string
}
dec := json.NewDecoder(strings.NewReader(jsonStream))
for {
    var m Message
    if err := dec.Decode(&m); err == io.EOF {
        break
    } else if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("%s: %s\n", m.Name, m.Text)
}

Ed: Knock knock.
Sam: Who's there?
Ed: Go fmt.
Sam: Go fmt who?
Ed: Go fmt yourself!

func NewDecoder

func NewDecoder(r io.Reader) *Decoder

NewDecoder returns a new decoder that reads from r.

The decoder introduces its own buffering and may read data from r beyond the JSON values requested.

func (*Decoder) Decode

func (dec *Decoder) Decode(v interface{}) error

Decode reads the next JSON-encoded value from its input and stores it in the value pointed to by v.

See the documentation for Unmarshal for details about the conversion of JSON into a Go value.

type Encoder

type Encoder struct {
    // contains filtered or unexported fields
}

An Encoder writes JSON objects to an output stream.

func NewEncoder

func NewEncoder(w io.Writer) *Encoder

NewEncoder returns a new encoder that writes to w.

func (*Encoder) Encode

func (enc *Encoder) Encode(v interface{}) error

Encode writes the JSON encoding of v to the connection.

See the documentation for Marshal for details about the conversion of Go values to JSON.

type InvalidUTF8Error

type InvalidUTF8Error struct {
    S string
}

func (*InvalidUTF8Error) Error

func (e *InvalidUTF8Error) Error() string

type InvalidUnmarshalError

type InvalidUnmarshalError struct {
    Type reflect.Type
}

An InvalidUnmarshalError describes an invalid argument passed to Unmarshal. (The argument to Unmarshal must be a non-nil pointer.)

func (*InvalidUnmarshalError) Error

func (e *InvalidUnmarshalError) Error() string

type Marshaler

type Marshaler interface {
    MarshalJSON() ([]byte, error)
}

Marshaler is the interface implemented by objects that can marshal themselves into valid JSON.

type MarshalerError

type MarshalerError struct {
    Type reflect.Type
    Err  error
}

func (*MarshalerError) Error

func (e *MarshalerError) Error() string

type RawMessage

type RawMessage []byte

RawMessage is a raw encoded JSON object. It implements Marshaler and Unmarshaler and can be used to delay JSON decoding or precompute a JSON encoding.

func (*RawMessage) MarshalJSON

func (m *RawMessage) MarshalJSON() ([]byte, error)

MarshalJSON returns *m as the JSON encoding of m.

func (*RawMessage) UnmarshalJSON

func (m *RawMessage) UnmarshalJSON(data []byte) error

UnmarshalJSON sets *m to a copy of data.

type SyntaxError

type SyntaxError struct {
    Offset int64 // error occurred after reading Offset bytes
    // contains filtered or unexported fields
}

A SyntaxError is a description of a JSON syntax error.

func (*SyntaxError) Error

func (e *SyntaxError) Error() string

type UnmarshalFieldError

type UnmarshalFieldError struct {
    Key   string
    Type  reflect.Type
    Field reflect.StructField
}

An UnmarshalFieldError describes a JSON object key that led to an unexported (and therefore unwritable) struct field.

func (*UnmarshalFieldError) Error

func (e *UnmarshalFieldError) Error() string

type UnmarshalTypeError

type UnmarshalTypeError struct {
    Value string       // description of JSON value - "bool", "array", "number -5"
    Type  reflect.Type // type of Go value it could not be assigned to
}

An UnmarshalTypeError describes a JSON value that was not appropriate for a value of a specific Go type.

func (*UnmarshalTypeError) Error

func (e *UnmarshalTypeError) Error() string

type Unmarshaler

type Unmarshaler interface {
    UnmarshalJSON([]byte) error
}

Unmarshaler is the interface implemented by objects that can unmarshal a JSON description of themselves. The input can be assumed to be a valid JSON object encoding. UnmarshalJSON must copy the JSON data if it wishes to retain the data after returning.

type UnsupportedTypeError

type UnsupportedTypeError struct {
    Type reflect.Type
}

func (*UnsupportedTypeError) Error

func (e *UnsupportedTypeError) Error() string

type UnsupportedValueError

type UnsupportedValueError struct {
    Value reflect.Value
    Str   string
}

func (*UnsupportedValueError) Error

func (e *UnsupportedValueError) Error() string