json

package
v1.0.6 Latest Latest
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 Go to latest Published: Oct 12, 2019 License: MIT, BSD-3-Clause Imports: 16 Imported by: 0

Documentation

Index

Examples

Constants

This section is empty.

Variables

This section is empty.

Functions

func CamelStyle 

func CamelStyle()

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 <, >, &, 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 

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 does not begin with the prefix nor any indentation, to make it easier to embed inside other formatted JSON data. Although leading space characters (space, tab, carriage return, newline) at the beginning of src are dropped, trailing space characters at the end of src are preserved and copied to dst. For example, if src has no trailing spaces, neither will dst; if src ends in a trailing newline, so will dst.

Example 
package main

import (
	"bytes"
	"log"
	"os"

	"github.com/zxfonline/misc/json"
)

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 

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

import (
	"fmt"
	"os"

	"github.com/zxfonline/misc/json"
)

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 

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

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

func UnderScoreStyle 

func UnderScoreStyle()

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 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. Unmarshal will only set exported fields of the struct.

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

To unmarshal a JSON array into a slice, Unmarshal resets the slice length to zero and then appends each element to the slice. As a special case, to unmarshal an empty JSON array into a slice, Unmarshal replaces the slice with a new empty slice.

To unmarshal a JSON array into a Go array, Unmarshal decodes JSON array elements into corresponding Go array elements. If the Go array is smaller than the JSON array, the additional JSON array elements are discarded. If the JSON array is smaller than the Go array, the additional Go array elements are set to zero values.

To unmarshal a JSON object into a string-keyed map, Unmarshal first establishes a map to use, If the map is nil, Unmarshal allocates a new map. Otherwise Unmarshal reuses the existing map, keeping existing entries. Unmarshal then stores key-value pairs from the JSON object into the map.

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 unmarshaling 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 (
	"fmt"

	"github.com/zxfonline/misc/json"
)

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 (
	"fmt"
	"io"
	"log"
	"strings"

	"github.com/zxfonline/misc/json"
)

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 

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) Buffered 

func (dec *Decoder) Buffered() io.Reader

Buffered returns a reader of the data remaining in the Decoder's buffer. The reader is valid until the next call to Decode.

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.

Example (Stream)

This example uses a Decoder to decode a streaming array of JSON objects. 

package main

import (
	"fmt"
	"log"
	"strings"

	"github.com/zxfonline/misc/json"
)

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))

	// read open bracket
	t, err := dec.Token()
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("%T: %v\n", t, t)

	var m Message
	// while the array contains values
	for dec.More() {

		// decode an array value (Message)
		err := dec.Decode(&m)
		if err != nil {
			log.Fatal(err)
		}

		fmt.Printf("%v: %v\n", m.Name, m.Text)
	}

	// read closing bracket
	t, err = dec.Token()
	if err != nil {
		log.Fatal(err)
	}
	fmt.Printf("%T: %v\n", t, t)

}

Output:

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

func (*Decoder) More 

func (dec *Decoder) More() bool

More reports whether there is another element in the current array or object being parsed.

func (*Decoder) Token 

func (dec *Decoder) Token() (Token, error)

Token returns the next JSON token in the input stream. At the end of the input stream, Token returns nil, io.EOF.

Token guarantees that the delimiters [ ] { } it returns are properly nested and matched: if Token encounters an unexpected delimiter in the input, it will return an error.

The input stream consists of basic JSON values—bool, string, number, and null—along with delimiters [ ] { } of type Delim to mark the start and end of arrays and objects. Commas and colons are elided.

Example

This example uses a Decoder to decode a stream of distinct JSON values. 

package main

import (
	"fmt"
	"io"
	"log"
	"strings"

	"github.com/zxfonline/misc/json"
)

func main() {
	const jsonStream = `
		{"Message": "Hello", "Array": [1, 2, 3], "Null": null, "Number": 1.234}
	`
	dec := json.NewDecoder(strings.NewReader(jsonStream))
	for {
		t, err := dec.Token()
		if err == io.EOF {
			break
		}
		if err != nil {
			log.Fatal(err)
		}
		fmt.Printf("%T: %v", t, t)
		if dec.More() {
			fmt.Printf(" (more)")
		}
		fmt.Printf("\n")
	}
}

Output:

json.Delim: { (more)
string: Message (more)
string: Hello (more)
string: Array (more)
json.Delim: [ (more)
float64: 1 (more)
float64: 2 (more)
float64: 3
json.Delim: ] (more)
string: Null (more)
<nil>: <nil> (more)
string: Number (more)
float64: 1.234
json.Delim: }

func (*Decoder) UseNumber 

func (dec *Decoder) UseNumber()

UseNumber causes the Decoder to unmarshal a number into an interface{} as a Number instead of as a float64.

type Delim 

type Delim rune

A Delim is a JSON array or object delimiter, one of [ ] { or }.

func (Delim) String 

func (d Delim) String() string

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 

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 stream, followed by a newline character.

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

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 

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 Number 

type Number string

A Number represents a JSON number literal.

func (Number) Float64 

func (n Number) Float64() (float64, error)

Float64 returns the number as a float64.

func (Number) Int64 

func (n Number) Int64() (int64, error)

Int64 returns the number as an int64.

func (Number) String 

func (n Number) String() string

String returns the literal text of the number.

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 (
	"fmt"
	"log"

	"github.com/zxfonline/misc/json"
)

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 Token 

type Token interface{}

A Token holds a value of one of these types: 

Delim, for the four JSON delimiters [ ] { }
bool, for JSON booleans
float64, for JSON numbers
Number, for JSON numbers
string, for JSON string literals
nil, for JSON null

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
	Offset int64        // error occurred after reading Offset bytes
}

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 encoding of a JSON value. UnmarshalJSON must copy the JSON data if it wishes to retain the data after returning.

type UnsupportedTypeError 

type UnsupportedTypeError struct {
	Type reflect.Type
}

An UnsupportedTypeError is returned by Marshal when attempting to encode an unsupported value 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

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