94 lines
2.5 KiB
Go
94 lines
2.5 KiB
Go
|
package main
|
||
|
|
|
||
|
|
import (
|
||
|
|
"encoding/json"
|
||
|
|
"fmt"
|
||
|
|
"os"
|
||
|
|
)
|
||
|
|
|
||
|
|
// demonstrate encoding and decoding of custom types below
|
||
|
|
type response1 struct {
|
||
|
|
Page int
|
||
|
|
Fruits []string
|
||
|
|
}
|
||
|
|
|
||
|
|
// only exported fields will be encoded/decoded in JSON
|
||
|
|
// Fields must start with capital letters to be exported
|
||
|
|
type response2 struct {
|
||
|
|
Page int `json:"page"`
|
||
|
|
Fruits []string `json:"fruits"`
|
||
|
|
}
|
||
|
|
|
||
|
|
// Go offers built-in support for JSON encoding and decoding, including to and from built-in and custom data types
|
||
|
|
func main() {
|
||
|
|
// encoding basic data types to JSON strings
|
||
|
|
bolB, _ := json.Marshal(true)
|
||
|
|
fmt.Println(string(bolB))
|
||
|
|
|
||
|
|
intB, _ := json.Marshal(1)
|
||
|
|
fmt.Println(string(intB))
|
||
|
|
|
||
|
|
fltB, _ := json.Marshal(2.34)
|
||
|
|
fmt.Println(string(fltB))
|
||
|
|
|
||
|
|
strB, _ := json.Marshal("gopher")
|
||
|
|
fmt.Println(string(strB))
|
||
|
|
|
||
|
|
// some for slices and maps, which encode to JSON arrays and objects
|
||
|
|
slcD := []string{"apple", "peach", "pear"}
|
||
|
|
slcB, _ := json.Marshal(slcD)
|
||
|
|
fmt.Println(string(slcB))
|
||
|
|
|
||
|
|
mapD := map[string]int{"apple": 5, "lettuce": 7}
|
||
|
|
mapB, _ := json.Marshal(mapD)
|
||
|
|
fmt.Println(string(mapB))
|
||
|
|
|
||
|
|
// the JSON package can automatically encode your custom data types
|
||
|
|
// it will only include exported fields in the encoded output and will by default use those names as the JSON keys
|
||
|
|
res1D := &response1{
|
||
|
|
Page: 1,
|
||
|
|
Fruits: []string{"apple", "peach", "pear"}}
|
||
|
|
res1B, _ := json.Marshal(res1D)
|
||
|
|
fmt.Println(string(res1B))
|
||
|
|
|
||
|
|
// use tags on struct field declarations to customize the encoded JSON key names
|
||
|
|
res2D := &response2{
|
||
|
|
Page: 1,
|
||
|
|
Fruits: []string{"apple", "peach", "pear"}}
|
||
|
|
res2B, _ := json.Marshal(res2D)
|
||
|
|
fmt.Println(string(res2B))
|
||
|
|
|
||
|
|
// generic decoding JSON data into Go values
|
||
|
|
byt := []byte(`{"num":6.13,"strs":["a","b"]}`)
|
||
|
|
|
||
|
|
// provide a variable where the JSON package can put the decoded data
|
||
|
|
var dat map[string]interface{}
|
||
|
|
|
||
|
|
// actual decoding, and a check for associated errors
|
||
|
|
if err := json.Unmarshal(byt, &dat); err != nil {
|
||
|
|
panic(err)
|
||
|
|
}
|
||
|
|
fmt.Println(dat)
|
||
|
|
|
||
|
|
// in order to use the values in the decoded map, convert them to their appropriate type
|
||
|
|
num := dat["num"].(float64)
|
||
|
|
fmt.Println(num)
|
||
|
|
|
||
|
|
// accessing nested data requires a series of conversions
|
||
|
|
strs := dat["strs"].([]interface{})
|
||
|
|
str1 := strs[0].(string)
|
||
|
|
fmt.Println(str1)
|
||
|
|
|
||
|
|
// decode JSON into custom data types
|
||
|
|
str := `{"page": 1, "fruits": ["apple", "peach"]}`
|
||
|
|
res := response2{}
|
||
|
|
json.Unmarshal([]byte(str), &res)
|
||
|
|
fmt.Println(res)
|
||
|
|
fmt.Println(res.Fruits[0])
|
||
|
|
|
||
|
|
// stream JSON encodings directly to os.Writers
|
||
|
|
enc := json.NewEncoder(os.Stdout)
|
||
|
|
d := map[string]int{"apple": 5, "lettuce": 7}
|
||
|
|
enc.Encode(d)
|
||
|
|
}
|