Go JSON 轉化規則

Go語言內置encoding/json包支持JSON序列化和反序列化，有以下轉換規則

• 基本的數據結構映射關係

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

• 當有指針出如今數據結構中時，會轉換成指針所指的值。
• chanel，complex和函數不能轉化爲有效的JSON文本
• JSON序列化時，須要定義一個struct結構，支持json tag來擴展功能, 對於未知的json數據結構，支持interface{}做爲接收容器

type Computer struct {
  Brand string
  // -：不要解析這個字段
  Name string `json: "-"`
  // omitempty： 字段爲0值時，不要解析
  Price float32 `json: "omitempty"`
  // 能夠替換的字段
  IsSupportAntCreditPay bool  `json: "huabei,omitempty"`
  HardwareConfiguration []string 
}

• JSON的流式讀寫

func NewDecoder(r io.Reader) *Decoder
func NewEncoder(w io.Writer) *Encoder

實例

package main

import (
	"fmt"
	"encoding/json"
)

type Computer struct {
  Brand string
  Name string
  Price float64
  // 能夠替換的字段
  IsSupportAntCreditPay bool  `json: "huabei`
  HardwareConfiguration []string 
}

func main() {
  hc := []string{"RTX2080Ti", "i9-9900k", "32G", "DDR4 XMP", "512G SSD"}
	alienware := Computer {
    Brand: "Alienware",
    Name: "外星人ALWS-R4968S",
    Price: 0,
    IsSupportAntCreditPay:false,
    HardwareConfiguration: hc}
  if b, err := json.Marshal(alienware); err !=nil {
    return 
  } else {  
    fmt.Println(b)
    fmt.Println()
    var computer Computer
    b := []byte(`{
      "Brand": "Alienware",
      "Name": "外星人ALWS-R4968S",
      "Price": 0.0,
      "huabei": "true",
      "HardwareConfiguration": ["i7-8700K", "GTX 1080Ti"]
    }`)
    if err:= json.Unmarshal(b, &computer); err == nil {
      fmt.Println(computer)
      fmt.Println()
    } else {
      fmt.Println(err)
      fmt.Println()
    }
    var unknowJson interface{}
    if err:= json.Unmarshal(b, &unknowJson); err == nil {
      unknowJson, ok := unknowJson.(map[string]interface{})
      if ok {
        for k, v := range unknowJson {
          switch t := v.(type) {
            case string:
              fmt.Println("string:", k, " ", v)
            case float64:
              fmt.Println("float:", k, " ", v)
            case bool:
              fmt.Println("bool:", k, " ", v)
            case []interface{}:
              fmt.Println(k, "is an array:")
              for i, iv := range t {
                fmt.Println(i, iv)
              }
            default:
              fmt.Println("unknow type:", k)
          }
        }
      }
    }
  }
}