Go语言基础: JSON序列化
JSON 是一种轻量级的数据交换格式。简洁和清晰的层次结构使得 JSON 成为理想的数据交换语言。 易于人阅读和编写，同时也易于机器解析和生成，并有效地提升网络传输效率。
首先得熟悉结构体:
package main
import "fmt"
type Student struct {
ID int
Gender string
Name string
Sno string
}
func main() {
var s = Student{
ID: 12,
Gender: "男",
Name: "李四",
Sno: "001",
}
fmt.Printf("%#v\n", s)
}
如上代码中定义了一个结构体并且打印
结果: main.Student{ID:12, Gender:"男", Name:"李四", Sno:"001"}
转化为JSON字符串
package main
import (
"encoding/json"
"fmt"
)
type Student struct {
ID int
Gender string
Name string
Sno string
}
func main() {
var s = Student{
ID: 12,
Gender: "男",
Name: "李四",
Sno: "001",
}
// fmt.Printf("%#v\n", s)
jsonbByte, _ := json.Marshal(s)
jsonStr := string(jsonbByte)
fmt.Println(jsonStr)
}
json.Marshal返回的是一个Byte类型的切片:
package json // import "encoding/json"
func Marshal(v any) ([]byte, error)
Marshal returns the JSON encoding of v.
然后用string将其转为字符串并打印
那么JSON字符串也可以转化为结构体
package main
import (
"encoding/json"
"fmt"
)
type Student struct {
ID int
Gender string
Name string
Sno string
}
func main() {
// 使用反引号就无须转义字符
var str = `{"ID":12,"Gender":"男","Name":"李四","Sno":"001"}`
var s Student
err := json.Unmarshal([]byte(str), &s)
if err != nil {
fmt.Println(err)
}
fmt.Printf("%#v", s)
}
这里用到Unmarshal函数来转换JSON字符串
package json // import "encoding/json"
func Unmarshal(data []byte, v any) error
Unmarshal parses the JSON-encoded data and stores the result in the value
pointed to by v. If v is nil or not a pointer, Unmarshal returns an
InvalidUnmarshalError.
代码中Unmarshal函数接收两个参数，第一个是字节类型的切片，第二个是结构体变量地址。
要注意的是，如果结构体中的某字段的首字母是小写的，那么是不能转化为JSON字符串的，因为是该字段是私有的。
可以利用结构体标签来更改JSON字符串中的key的形式
package main
import (
"encoding/json"
"fmt"
)
type Student struct {
ID int `json:"id"` // 添加了结构体标签
Gender string `json:"gender"`
Name string `json:"name"`
Sno string `json:"sno"`
}
func main() {
var s = Student{
ID: 12,
Gender: "男",
Name: "李四",
Sno: "001",
}
// fmt.Printf("%#v\n", s)
jsonbByte, _ := json.Marshal(s)
jsonStr := string(jsonbByte)
fmt.Println(jsonStr)
}
打印结果: {"id":12,"gender":"男","name":"李四","sno":"001"}
显然这个形式已经与之前的不一样了，首字母已经被改成了小写，这就是结构体标签作用之一。
下面是嵌套结构体的转化
package main
import (
"encoding/json"
"fmt"
)
// Student 学生结构体
type Student struct {
ID int `json:"id"`
Gender string `json:"gender"`
Name string `json:"name"`
Sno string `json:"sno"`
}
// Class 班级结构体
type Class struct {
Title string
Students []Student
}
func main() {
c := Class{
Title: "001 Class",
Students: make([]Student, 0), // make创建切片
}
for i := 1; i < 10; i++ {
s := Student{
ID: i,
Gender: "男",
Name: fmt.Sprintf("stu_%v", i),
}
c.Students = append(c.Students, s) // 加入切片
}
fmt.Println(c)
strByte, err := json.Marshal(c)
if err != nil {
fmt.Println(err)
} else {
strJson := string(strByte)
fmt.Println(strJson)
}
}
打印结果
{001 Class [{1 男 stu_1 } {2 男 stu_2 } {3 男 stu_3 } {4 男 stu_4 } {5 男 stu_5 } {6 男 stu_6 } {7 男 stu_7 } {8 男 stu_8 } {9 男 stu_9 }]}
{"Title":"001 Class","Students":[{"id":1,"gender":"男","name":"stu_1","sno":""},{"id":2,"gender":"男","name":"stu_2","sno":""},{"id":3,"gender":"男","name":"stu_3","sno":""},{"id":4,"gender":"男","name":_4","sno":""},{"id":5,"gender":"男","name":"stu_5","sno":""},{"id":6,"gender":"男","name":"stu_6","sno":""},{"id":7,"gender":"男","name":"stu_7","sno":""},{"id":8,"gender":"男","name":"stu_8","sno":""},{:9,"gender":"男","name":"stu_9","sno":""}]}
第一行是结构体信息，其后才是JSON数据
在这个JSON中是数据嵌套存放的，看着比较乱，可以借助 JSON在线解析 解析该数据
解析结果:
{
"Title":"001 Class",
"Students":[
{
"id":1,
"gender":"男",
"name":"stu_1",
"sno":""
},
{
"id":2,
"gender":"男",
"name":"stu_2",
"sno":""
},
{
"id":3,
"gender":"男",
"name":"stu_3",
"sno":""
},
{
"id":4,
"gender":"男",
"name":"stu_4",
"sno":""
},
{
"id":5,
"gender":"男",
"name":"stu_5",
"sno":""
},
{
"id":6,
"gender":"男",
"name":"stu_6",
"sno":""
},
{
"id":7,
"gender":"男",
"name":"stu_7",
"sno":""
},
{
"id":8,
"gender":"男",
"name":"stu_8",
"sno":""
},
{
"id":9,
"gender":"男",
"name":"stu_9",
"sno":""
}
]
}
那么又如何将这个字符串再转化回去？
如下所示
package main
import (
"encoding/json"
"fmt"
)
// Student 学生结构体
type Student struct {
ID int `json:"id"`
Gender string `json:"gender"`
Name string `json:"name"`
Sno string `json:"sno"`
}
// Class 班级结构体
type Class struct {
Title string
Students []Student
}
func main() {
str := `{"Title":"001 Class","Students":[{"id":1,"gender":"男","name":"stu_1","sno":""},{"id":2,"gender":"男","name":"stu_2","sno":""},{"id":3,"gender":"男","name":"stu_3","sno":""},{"id":4,"gender":"男","name":"stu_4","sno":""},{"id":5,"gender":"男","name":"stu_5","sno":""},{"id":6,"gender":"男","name":"stu_6","sno":""},{"id":7,"gender":"男","name":"stu_7","sno":""},{"id":8,"gender":"男","name":"stu_8","sno":""},{"id":9,"gender":"男","name":"stu_9","sno":""}]}`
var c = &Class{} // 地址
err := json.Unmarshal([]byte(str), c)
if err != nil {
fmt.Println(err)
}
fmt.Printf("%#v", *c)
}
打印结果
main.Class{Title:"001 Class", Students:[]main.Student{main.Student{ID:1, Gender:"男", Name:"stu_1", Sno:""}, main.Student{ID:2, Gender:"男", Name:"stu_2", Sno:""}, main.Student{ID:3, Gender:"男", Name:"stu_3", Sno:""}, main.Student{ID:4, Gender:"男", Name:"stu_4", Sno:""}, main.Student{ID:5, Gender:"男", Name:"stu_5", Sno:""}, main.Student{ID:6, Gender:"男", Name:"stu_6", Sno:""}, main.Student{ID:7, Gender:"男", Name:"stu_7", Sno:""}, main.Student{ID:8, Gender:"男", Name:"stu_8", Sno:""}, main.Student{ID:9, Gender:"男", Name:"stu_9", Sno:""}}}
JSON序列化就是将结构体转化为JSON字符串
JSON反序列化就是将JSON字符串转化为结构体
