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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package json_test
import (
"bytes"
"encoding/json"
"fmt"
"io"
"log"
"os"
"strings"
)
func ExampleMarshal() {
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 ExampleUnmarshal() {
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}]
}
// This example uses a Decoder to decode a stream of distinct JSON values.
func ExampleDecoder() {
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!
}
// This example uses a Decoder to decode a stream of distinct JSON values.
func ExampleDecoder_Token() {
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: }
}
// This example uses a Decoder to decode a streaming array of JSON objects.
func ExampleDecoder_Decode_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))
// read open bracket
t, err := dec.Token()
if err != nil {
log.Fatal(err)
}
fmt.Printf("%T: %v\n", t, t)
// while the array contains values
for dec.More() {
var m Message
// 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: ]
}
// This example uses RawMessage to delay parsing part of a JSON message.
func ExampleRawMessage_unmarshal() {
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 any
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}
}
// This example uses RawMessage to use a precomputed JSON during marshal.
func ExampleRawMessage_marshal() {
h := json.RawMessage(`{"precomputed": true}`)
c := struct {
Header *json.RawMessage `json:"header"`
Body string `json:"body"`
}{Header: &h, Body: "Hello Gophers!"}
b, err := json.MarshalIndent(&c, "", "\t")
if err != nil {
fmt.Println("error:", err)
}
os.Stdout.Write(b)
// Output:
// {
// "header": {
// "precomputed": true
// },
// "body": "Hello Gophers!"
// }
}
func ExampleIndent() {
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 ExampleMarshalIndent() {
data := map[string]int{
"a": 1,
"b": 2,
}
b, err := json.MarshalIndent(data, "<prefix>", "<indent>")
if err != nil {
log.Fatal(err)
}
fmt.Println(string(b))
// Output:
// {
// <prefix><indent>"a": 1,
// <prefix><indent>"b": 2
// <prefix>}
}
func ExampleValid() {
goodJSON := `{"example": 1}`
badJSON := `{"example":2:]}}`
fmt.Println(json.Valid([]byte(goodJSON)), json.Valid([]byte(badJSON)))
// Output:
// true false
}
func ExampleHTMLEscape() {
var out bytes.Buffer
json.HTMLEscape(&out, []byte(`{"Name":"<b>HTML content</b>"}`))
out.WriteTo(os.Stdout)
// Output:
//{"Name":"\u003cb\u003eHTML content\u003c/b\u003e"}
}