Go如何实现json字符串与各类struct相互转换

 
package main 
import (
   "fmt"
   "reflect"
   "encoding/json"
   "strings"
)
 
type Class struct {
   Grade int `json:"grade"` //年级
   ClassNumber int  `json:"classNumber"` //班级号
}
 
type Student struct{
   Name string  //大写开头，可被导出，没有`json:".."`，导出json的字段名是原本名称
   age int  //小写开题，不可被导出
   Hight int `json:"currentHight"` //导出对应json的字段名为currentHight
   Class *Class `class` //指针，指向引用对象；如果不用指针，只是值复制
}
 
func doMarshal(){//对象转json字符串
   nClass:=new(Class)//new只给给特定类型分配内存，设置“零”值，返回其地址（指针）
   fmt.Printf("nClass的类型是%s,内容是%v\n",reflect.TypeOf(nClass),*nClass)
   nClass.Grade=3
   nClass.ClassNumber=6
   nStudents:=make([]*Student,0)
   //make只用于map，slice和channel，并且不显示返回指针
   //这个切片，存放Student的指针
   nStudent:=Student{"Lily",7,116,nClass}
   jsonBytes,err1:=json.Marshal(nStudent)//解析后的是[]byte
   if err1!=nil{
      fmt.Printf("转json失败：%v\n",err1)
      return
   }
   fmt.Println("转成的JSON：") //age不会被导出
   //{"Name":"Lily","currentHight":116,"Class":{"grade":3,"classNumber":6}}
   fmt.Println(string(jsonBytes))
   nStudents=append(nStudents,&Student{"Lilei",8,130,nClass})
   nStudents=append(nStudents,&nStudent)
   josnListBytes,err2:=json.Marshal(nStudents)
   if err2!=nil{
      fmt.Printf("转jsonList失败：%v\n",err2)
      return
   }
   fmt.Println("转成的列表型JSON：")
   fmt.Println(string(josnListBytes))
   //[{"Name":"Lilei","currentHight":130,"Class":{"grade":3,"classNumber":6}},{"Name":"Lily","currentHight":116,"Class":{"grade":3,"classNumber":6}}]
}
 
func doUnMarshal(){//json字符串转对象
   jsonStr:=`
      {
         "Name":"Lily",
         "currentHight":116,
         "age":12,
         "Class":{
            "grade":3,
            "classNumber":6
         },
         "score":[98,100,95]
      }
   `
   jsonListStr:=`[
      {
         "Name":"Lucy",
         "currentHight":120,
         "Class":{
            "grade":3,
            "classNumber":5
         }
      },
      {
         "Name":"Lily",
         "currentHight":116,
         "Class":{
            "grade":3,
            "classNumber":6
         }
      }
   ]`
   //第一种解析json方式，解析到Struct/[]Struct
   student:=Student{}//同new(Student)
   err:=json.Unmarshal([]byte(jsonStr),&student)
   //Unmarshall第2个参数必须是指针，否则报错：json: Unmarshal(non-pointer main.Student)
   //因为必须解析到具体的对象，所以需传入对象引用，而不是值传递
   //score在Student中没有此字段，所以被忽略了
   if err!=nil{
      fmt.Printf("解析json字符串异常：%s\n",err)
   }
   fmt.Printf("学生的名称是%v,班级信息是%v,年龄是%v（私有对象不能导入，初始为0）\n",student.Name,*student.Class,student.age)
   //学生的名称是Lily,学生的班级信息是{3 6},学生的年龄是0
   students:=[]*Student{} //定义切片，同make([]*Student,0)
   err=json.Unmarshal([]byte(jsonListStr),&students)
   if err!=nil{
      fmt.Printf("解析json字符串异常：%s\n",err)
   }
   for _,stu:=range students{ //这里stu是指针类型，获取其属性可以直接用.Name，也可以解引用后用.Name
      fmt.Printf("列表：学生的名称是%s,身高是%d,在%d年级%d班\n",stu.Name,(*stu).Hight,(*stu.Class).Grade,stu.Class.ClassNumber)
   }
   //第二种解析到interface{}/[]interface{}
   fmt.Println("*************解析json*************")
   var student1 interface{}
   err=json.Unmarshal([]byte(jsonStr),&student1)
   if err!=nil{
      fmt.Printf("解析json字符串异常：%s\n",err)
   }
   c:=-1
   resolve2JosnObj(student1,c)
   
   fmt.Println("*************解析jsonlist*************")
   var students1 interface{}
   err=json.Unmarshal([]byte(jsonListStr),&students1)
   if err!=nil{
      fmt.Printf("解析jsonlist字符串异常：%s\n",err)
   }
   d:=-1
   resolve2JosnObj(students1,d)
   
}
 
func resolve2JosnObj(objI interface{},c int){
   c=c+1
   switch obj:=objI.(type) { //此处[interface{}].(type) 专门用于switch的类型判断
   case string:
      fmt.Println("类型是string，值是",obj)
   case float64:
      fmt.Println("类型float64，值是",obj)
   case map[string]interface{}:
      fmt.Println("map元素：")
      for k,vi:=range obj{
         fmt.Printf("%smap[%s]的元素: ",strings.Repeat("---",c),k)
         resolve2JosnObj(vi,c)
      }
   case []interface{}:
      fmt.Println("list元素：")
      for i,vi:=range obj{
         fmt.Printf("%s第%d个元素: ",strings.Repeat("---",c),i)
         resolve2JosnObj(vi,c)
      }
 
   default:
      fmt.Println("无法判断类型，类型是",reflect.TypeOf(obj),"值是",obj) 
   } 
}
 
func main() {
   doMarshal()//对象转json字符串
   doUnMarshal()
}

package main
import (
	"encoding/json"
	"fmt"
)
type Student struct {
	Name string
	age int
}
func main() {
	var s Student = Student {
		Name: "xiaomo",
		age: 18,
	}
	fmt.Printf("%+v\n", s)
	res, _ := json.Marshal(s)
	fmt.Println(string(res))
}