Documentation
¶
Overview ¶
Package json implements encoding and decoding of JSON objects as defined in RFC 4627. The mapping between JSON objects and Go values is described in the documentation for the Marshal and Unmarshal functions.
See "JSON and Go" for an introduction to this package: http://golang.org/doc/articles/json_and_go.html
Index ¶
- func CamelStyle()
- 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 UnderScoreStyle()
- func Unmarshal(data []byte, v interface{}) error
- func UpperCamelStyel()
- type Decoder
- type EncodeNameStyle
- type Encoder
- type InvalidUTF8Error
- type InvalidUnmarshalError
- type Marshaler
- type MarshalerError
- type Number
- type RawMessage
- type SyntaxError
- type UnmarshalFieldError
- type UnmarshalTypeError
- type Unmarshaler
- type UnsupportedTypeError
- type UnsupportedValueError
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func CamelStyle ¶
func CamelStyle()
func Compact ¶
Compact appends to dst the JSON-encoded src with insignificant space characters elided.
func HTMLEscape ¶
HTMLEscape appends to dst the JSON-encoded src with <, >, &, U+2028 and U+2029 characters inside string literals changed to \u003c, \u003e, \u0026, \u2028, \u2029 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 ¶
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 does not begin with the prefix nor any indentation, and has no trailing newline, to make it easier to embed inside other formatted JSON data.
Example ¶
package main
import (
"bytes"
"encoding/json"
"log"
"os"
)
func main() {
type Road struct {
Name string
Number int
}
roads := []Road{
{"Diamond Fork", 29},
{"Sheep Creek", 51},
}
b, err := json.Marshal(roads)
if err != nil {
log.Fatal(err)
}
var out bytes.Buffer
json.Indent(&out, b, "=", "\t")
out.WriteTo(os.Stdout)
}
Output: [ = { = "Name": "Diamond Fork", = "Number": 29 = }, = { = "Name": "Sheep Creek", = "Number": 51 = } =]
func Marshal ¶
Example ¶
package main
import (
"encoding/json"
"fmt"
"os"
)
func main() {
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)
}
Output: {"ID":1,"Name":"Reds","Colors":["Crimson","Red","Ruby","Maroon"]}
func MarshalIndent ¶
MarshalIndent is like Marshal but applies Indent to format the output.
func UnderScoreStyle ¶
func UnderScoreStyle()
func Unmarshal ¶
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 a struct, Unmarshal matches incoming object keys to the keys used by Marshal (either the struct field name or its tag), preferring an exact match but also accepting a case-insensitive match.
To unmarshal JSON into an interface value, 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.
The JSON null value unmarshals into an interface, map, pointer, or slice by setting that Go value to nil. Because null is often used in JSON to mean “not present,” unmarshaling a JSON null into any other Go type has no effect on the value and produces no error.
When unmarshaling quoted strings, invalid UTF-8 or invalid UTF-16 surrogate pairs are not treated as an error. Instead, they are replaced by the Unicode replacement character U+FFFD.
Example ¶
package main
import (
"encoding/json"
"fmt"
)
func main() {
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)
}
Output: [{Name:Platypus Order:Monotremata} {Name:Quoll Order:Dasyuromorphia}]
func UpperCamelStyel ¶
func UpperCamelStyel()
Types ¶
type Decoder ¶
type Decoder struct {
// contains filtered or unexported fields
}
A Decoder reads and decodes JSON objects from an input stream.
Example ¶
This example uses a Decoder to decode a stream of distinct JSON values.
package main
import (
"encoding/json"
"fmt"
"io"
"log"
"strings"
)
func main() {
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)
}
}
Output: Ed: Knock knock. Sam: Who's there? Ed: Go fmt. Sam: Go fmt who? Ed: Go fmt yourself!
func NewDecoder ¶
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) Buffered ¶
Buffered returns a reader of the data remaining in the Decoder's buffer. The reader is valid until the next call to Decode.
type EncodeNameStyle ¶
type EncodeNameStyle int
type Encoder ¶
type Encoder struct {
// contains filtered or unexported fields
}
An Encoder writes JSON objects to an output stream.
func NewEncoder ¶
NewEncoder returns a new encoder that writes to w.
type InvalidUTF8Error ¶
type InvalidUTF8Error struct {
S string // the whole string value that caused the error
}
Before Go 1.2, an InvalidUTF8Error was returned by Marshal when attempting to encode a string value with invalid UTF-8 sequences. As of Go 1.2, Marshal instead coerces the string to valid UTF-8 by replacing invalid bytes with the Unicode replacement rune U+FFFD. This error is no longer generated but is kept for backwards compatibility with programs that might mention it.
func (*InvalidUTF8Error) Error ¶
func (e *InvalidUTF8Error) Error() string
type InvalidUnmarshalError ¶
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 ¶
Marshaler is the interface implemented by objects that can marshal themselves into valid JSON.
type MarshalerError ¶
func (*MarshalerError) Error ¶
func (e *MarshalerError) Error() string
type Number ¶
type Number string
A Number represents a JSON number literal.
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.
Example ¶
This example uses RawMessage to delay parsing part of a JSON message.
package main
import (
"encoding/json"
"fmt"
"log"
)
func main() {
type Color struct {
Space string
Point json.RawMessage // delay parsing until we know the color space
}
type RGB struct {
R uint8
G uint8
B uint8
}
type YCbCr struct {
Y uint8
Cb int8
Cr int8
}
var j = []byte(`[
{"Space": "YCbCr", "Point": {"Y": 255, "Cb": 0, "Cr": -10}},
{"Space": "RGB", "Point": {"R": 98, "G": 218, "B": 255}}
]`)
var colors []Color
err := json.Unmarshal(j, &colors)
if err != nil {
log.Fatalln("error:", err)
}
for _, c := range colors {
var dst interface{}
switch c.Space {
case "RGB":
dst = new(RGB)
case "YCbCr":
dst = new(YCbCr)
}
err := json.Unmarshal(c.Point, dst)
if err != nil {
log.Fatalln("error:", err)
}
fmt.Println(c.Space, dst)
}
}
Output: YCbCr &{255 0 -10} RGB &{98 218 255}
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. (No longer used; kept for compatibility.)
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 ¶
Unmarshaler is the interface implemented by objects that can unmarshal a JSON description of themselves. The input can be assumed to be a valid encoding of a JSON value. UnmarshalJSON must copy the JSON data if it wishes to retain the data after returning.
type UnsupportedTypeError ¶
An UnsupportedTypeError is returned by Marshal when attempting to encode an unsupported value type.
func (*UnsupportedTypeError) Error ¶
func (e *UnsupportedTypeError) Error() string
type UnsupportedValueError ¶
func (*UnsupportedValueError) Error ¶
func (e *UnsupportedValueError) Error() string