golang-自定义json序列化和反序列化

为某个类型实现MarshalJSON()([]byte, error)和UnmarshalJSON(b []byte) error方法，那么该类型在序列化和反序列化时就会使用相应方法。
未自定义前代码：

package main

import (
	"encoding/json"
	"fmt"
	"time"
)

type Student struct {
	Name       string    `json:"name"`
	Age        int       `json:"age"`
	Weight     float64   `json:"weight"`
	Height     float64   `json:"height"`
	RecordTime time.Time `json:"recordtime"`
}

func main() {

	s1 := Student{
		Name:       "jack",
		Age:        20,
		Weight:     61.5,
		Height:     172.5,
		RecordTime: time.Now(),
	}

	b, err := json.Marshal(s1)
	if err != nil {
		fmt.Printf("json.Marshal failed, err:%v\n", err)
		return
	}
	fmt.Printf("s1: %s\n", b)

	var s2 Student
	err = json.Unmarshal(b, &s2)
	if err != nil {
		fmt.Printf("json.Unmarshal failed, err:%v\n", err)
		return
	}
	fmt.Printf("s2: %#v\n", s2)
}

输出：

s1: {"name":"jack","age":20,"weight":61.5,"height":172.5,"recordtime":"2020-06-24T17:07:57.200873+08:00"}
s2: main.Student{Name:"jack", Age:20, Weight:61.5, Height:172.5, RecordTime:time.Time{wall:0xbf91428, ext:63728586477, loc:(*time.Location)(0x11d0d60)}}

自定义MarshalJSON()([]byte, error)和UnmarshalJSON(b []byte) error方法：

package main

import (
	"encoding/json"
	"fmt"
	"time"
)

type Student struct {
	Name       string    `json:"name"`
	Age        int       `json:"age"`
	Weight     float64   `json:"weight"`
	Height     float64   `json:"height"`
	RecordTime time.Time `json:"recordtime"`
}

const layout = "2006-01-02 15:04:05"

func (s *Student) MarshalJSON() ([]byte, error) {
	type TempStudent Student
	return json.Marshal(struct {
		RecordTime string `json:"recordtime"`
		*TempStudent
	}{
		RecordTime:  s.RecordTime.Format(layout),
		TempStudent: (*TempStudent)(s),
	})
}

func (s *Student) UnmarshalJSON(data []byte) error {
	type TempStudent Student

	ss := struct {
		RecordTime string `json:"recordtime"`
		*TempStudent
	}{
		TempStudent: (*TempStudent)(s),
	}

	if err := json.Unmarshal(data, &ss); err != nil {
		return err
	}

	var err error
	s.RecordTime, err = time.Parse(layout, ss.RecordTime)
	if err != nil {
		return err
	}

	return nil
}

func main() {

	s1 := Student{
		Name:       "jack",
		Age:        20,
		Weight:     61.5,
		Height:     172.5,
		RecordTime: time.Now(),
	}

	b, err := json.Marshal(&s1)
	if err != nil {
		fmt.Printf("json.Marshal failed, err:%v\n", err)
		return
	}
	fmt.Printf("s1: %s\n", b)

	var s2 Student
	err = json.Unmarshal(b, &s2)
	if err != nil {
		fmt.Printf("json.Unmarshal failed, err:%v\n", err)
		return
	}
	fmt.Printf("s2: %#v\n", s2)
}

输出：

s1: {"recordtime":"2020-06-24 17:41:14","name":"jack","age":20,"weight":61.5,"height":172.5}
s2: main.Student{Name:"jack", Age:20, Weight:61.5, Height:172.5, RecordTime:time.Time{wall:0x0, ext:63728617274, loc:(*time.Location)(nil)}}