Golang basic_leaming结构体和 Json 相互转换序列化反序列化

Posted 2023-01-14 知其黑、受其白

阅读目录

• 一、关于JSON 数据
• 二、结构体与JSON 序列化
• • 1、结构体对象转化成 Json 字符串
  • 2、Json 字符串转换成结构体对象
• 三、结构体标签 Tag
• 四、嵌套结构体和JSON 序列化反序列化

一、关于JSON 数据

JSON(javascript Object Notation) 是一种轻量级的数据交换格式。

易于人阅读和编写。

同时也易于机器解析和生成。

RESTfull Api 接口中返回的数据都是json 数据。

Json 的基本格式如下：

	"a": "Hello",
	"b": "World"

稍微复杂点的JSON。

	"result": [
		"_id": "59f6ef443ce1fb0fb02c7a43",
		"title": "笔记本电脑",
		"status": "1",
		"pic": "public\\\\upload\\\\UObZahqPYzFvx_C9CQjU8KiX.png",
		"url": "12"
	, 
		"_id": "5a012efb93ec4d199c18d1b4",
		"title": "第二个轮播图",
		"status": "1",
		"pic": "public\\\\upload\\\\f3OtH11ZaPX5AA4Ov95Q7DEM.png"
	, 
		"_id": "5a012f2433574208841e0820",
		"title": "第三个轮播图",
		"status": "1",
		"pic": "public\\\\upload\\\\s5ujmYBQVRcLuvBHvWFMJHzS.jpg"
	, 
		"_id": "5a688a0ca6dcba0ff4861a3d",
		"title": "教程",
		"status": "1",
		"pic": "public\\\\upload\\\\Zh8EP9HOasV28ynDSp8TaGwd.png"
	]

二、结构体与JSON 序列化

比如我们Golang 要给App 或者小程序提供Api 接口数据，这个时候就需要涉及到结构体和Json 之间的相互转换。

Golang JSON 序列化是指把结构体数据转化成JSON 格式的字符串，Golang JSON 的反序列化是指把JSON 数据转化成Golang 中的结构体对象。

Golang 中的序列化和反序列化主要通过 “encoding/json” 包中 json.Marshal() 和 json.Unmarshal() 方法实现。

1、结构体对象转化成 Json 字符串

package main

import (
	"encoding/json"
	"fmt"
)

type Student struct 
	ID     int
	Gender string
	name   string
	//私有属性不能被json 包访问
	Sno string


func main() 
	var s1 = Student
		ID:     1,
		Gender: "男",
		name:   "李四",
		Sno:    "s0001",
	
	fmt.Printf("%#v\\n", s1)
	// main.StudentID:1, Gender:"男", name:"李四", Sno:"s0001"

	var s, _ = json.Marshal(s1)
	jsonStr := string(s)
	fmt.Println(jsonStr)
	// "ID":1,"Gender":"男","Sno":"s0001"

2、Json 字符串转换成结构体对象

package main

import (
	"encoding/json"
	"fmt"
)

type Student struct 
	ID     int
	Gender string
	Name   string
	Sno    string


func main() 
	// var jsonStr = "\\"ID\\":1,\\"Gender\\":\\"男\\",\\"Name\\":\\"李四\\",\\"Sno\\":\\"s0001\\""
	var jsonStr = `"ID":1,"Gender":"男","Name":"李四","Sno":"s0001"`
	//定义一个Monster 实例
	var student Student
	err := json.Unmarshal([]byte(jsonStr), &student)
	if err != nil 
		fmt.Printf("unmarshal err=%v\\n", err)
	
	fmt.Printf("反序列化后student=%#v student.Name=%v \\n", student, student.Name)
	// 反序列化后student=main.StudentID:1, Gender:"男", Name:"李四", Sno:"s0001" student.Name=李四

三、结构体标签 Tag

Tag 是结构体的元信息，可以在运行的时候通过反射的机制读取出来。

Tag 在结构体字段的后方定义，由一对反引号包裹起来，具体的格式如下：

key1:"value1" key2:"value2"

结构体 tag 由一个或多个键值对组成。

键与值使用冒号分隔，值用双引号括起来。同一个结构体字段可以设置多个键值对 tag，不同的键值对之间使用空格分隔。

注意事项：
为结构体编写Tag 时，必须严格遵守键值对的规则。
结构体标签的解析代码的容错能力很差，一旦格式写错，编译和运行时都不会提示任何错误，通过反射也无法正确取值。
例如不要在key 和value 之间添加空格。

package main

import (
	"encoding/json"
	"fmt"
)

type Student struct 
	ID int `json:"id"`
	//通过指定tag 实现json 序列化该字段时的key
	Gender string `json:"gender"`
	Name   string
	Sno    string


func main() 
	var s1 = Student
		ID:     1,
		Gender: "男",
		Name:   "李四",
		Sno:    "s0001",
	
	fmt.Printf("%#v\\n", s1)
	// main.StudentID:1, Gender:"男", Name:"李四", Sno:"s0001"

	var s, _ = json.Marshal(s1)
	jsonStr := string(s)
	fmt.Println(jsonStr)
	// "id":1,"gender":"男","Name":"李四","Sno":"s0001"

package main

import (
	"encoding/json"
	"fmt"
)

type Student struct 
	ID int `json:"id"`
	//通过指定tag 实现json 序列化该字段时的key
	Gender string `json:"gender"`
	Name   string
	Sno    string


func main() 
	var s2 Student
	var str = "\\"id\\":1,\\"gender\\":\\"男\\",\\"Name\\":\\"李四\\",\\"Sno\\":\\"s0001\\""
	err := json.Unmarshal([]byte(str), &s2)
	if err != nil 
		fmt.Println(err)
	
	fmt.Printf("%#v", s2)
	// main.StudentID:0, Gender:"", Name:"", Sno:""

四、嵌套结构体和JSON 序列化反序列化

package main

import (
	"encoding/json"
	"fmt"
)

// Student 学生
type Student struct 
	ID     int
	Gender string
	Name   string


// Class 班级
type Class struct 
	Title    string
	Students []Student


func main() 
	c := &Class
		Title:    "001",
		Students: make([]Student, 0, 200),
	
	for i := 0; i < 10; i++ 
		stu := Student
			Name:   fmt.Sprintf("stu%02d", i),
			Gender: "男",
			ID:     i,
		
		c.Students = append(c.Students, stu)
	
	//JSON 序列化：结构体-->JSON 格式的字符串
	data, err := json.Marshal(c)
	if err != nil 
		fmt.Println("json marshal failed")
		return
	
	fmt.Printf("json:%s\\n", data)

	"Title": "001",
	"Students": [
		"ID": 0,
		"Gender": "男",
		"Name": "stu00"
	, 
		"ID": 1,
		"Gender": "男",
		"Name": "stu01"
	, 
		"ID": 2,
		"Gender": "男",
		"Name": "stu02"
	, 
		"ID": 3,
		"Gender": "男",
		"Name": "stu03"
	, 
		"ID": 4,
		"Gender": "男",
		"Name": "stu04"
	, 
		"ID": 5,
		"Gender": "男",
		"Name": "stu05"
	, 
		"ID": 6,
		"Gender": "男",
		"Name": "stu06"
	, 
		"ID": 7,
		"Gender": "男",
		"Name": "stu07"
	, 
		"ID": 8,
		"Gender": "男",
		"Name": "stu08"
	, 
		"ID": 9,
		"Gender": "男",
		"Name": "stu09"
	]

package main

import (
	"encoding/json"
	"fmt"
)

// Student 学生
type Student struct 
	ID     int
	Gender string
	Name   string


// Class 班级
type Class struct 
	Title    string
	Students []Student


func main() 
	str := `"Title":"001","Students":["ID":0,"Gender":"男","Name":"stu00","ID":1,"Gender":"男","Name":"stu01","ID":2,"Gender":"男","Name":"stu02","ID":3,"Gender":"男","Name":"stu03","ID":4,"Gender":"男","Name":"stu04","ID":5,"Gender":"男","Name":"stu05","ID":6,"Gender":"男","Name":"stu06","ID":7,"Gender":"男","Name":"stu07","ID":8,"Gender":"男","Name":"stu08","ID":9,"Gender":"男","Name":"stu09"]`
	c1 := &Class
	err := json.Unmarshal([]byte(str), c1)
	if err != nil 
		fmt.Println("json unmarshal failed!")
		return
	
	fmt.Printf("%#v\\n", c1)

running...
&main.ClassTitle:"001", Students:[]main.Studentmain.StudentID:0, Gender:"男", Name:"stu00", main.StudentID:1, Gender:"男", Name:"stu01", main.StudentID:2, Gender:"男", Name:"stu02", main.StudentID:3, Gender:"男", Name:"stu03", main.StudentID:4, Gender:"男", Name:"stu04", main.StudentID:5, Gender:"男", Name:"stu05", main.StudentID:6, Gender:"男", Name:"stu06", main.StudentID:7, Gender:"男", Name:"stu07", main.StudentID:8, Gender:"男", Name:"stu08", main.StudentID:9, Gender:"男", Name:"stu09"