Golang 【basic_leaming】结构体和 Json 相互转换序列化反序列化-CFANZ编程社区

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