Go: marshal []byte to JSON, giving a strange strin

问题:

When I try to marshal []byte to JSON format, I only got a strange string.

Please look the following code.

I have two doubt:

How can I marshal []byte to JSON?

Why []byte become this string?

package main

import (
    "encoding/json"
    "fmt"
    "os"
)

func main() {
    type ColorGroup struct {
        ByteSlice    []byte
        SingleByte   byte
        IntSlice     []int
    }
    group := ColorGroup{
        ByteSlice:  []byte{0,0,0,1,2,3},
        SingleByte: 10,
        IntSlice:   []int{0,0,0,1,2,3},
    }
    b, err := json.Marshal(group)
    if err != nil {
        fmt.Println("error:", err)
    }
    os.Stdout.Write(b)
}

the output is:

{"ByteSlice":"AAAAAQID","SingleByte":10,"IntSlice":[0,0,0,1,2,3]}

golang playground: https://play.golang.org/p/wanppBGzNR

回答1:

As per the docs: https://golang.org/pkg/encoding/json/#Marshal

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.

The value AAAAAQID is a base64 representation of your byte slice - e.g.

b, err := base64.StdEncoding.DecodeString("AAAAAQID")
if err != nil {
    log.Fatal(err)
}

fmt.Printf("%v", b)
// Outputs: [0 0 0 1 2 3]