gorm时间格式化

GORM自带的time.Time类型JSON默认输出RFC3339Nano格式的，但是如果想改为yyyy-MM-dd HH:mm:ss形式的时间格式，需要定制MarshalJSON了。

以下是数据库里存储的数据：

Go声明了一个LocalTime的别名，然后绑定了函数MarshalJSON，用于在序列化时调用。

package main

import (
  "database/sql/driver"
  "encoding/json"
  "fmt"
  _ "github.com/go-sql-driver/mysql"
  "gorm.io/driver/mysql"
  "gorm.io/gorm"
  "gorm.io/gorm/schema"
  "strings"
  "time"
)

type Student struct {
  Id       int
  Name     string
  Age      int
  Sex      string
  CreateAt time.Time
}

// TableName 指定表名
func (Student) TableName() string {
  return "student"
}

// LocalTime 别名
type LocalTime time.Time

func (t LocalTime) MarshalJSON() ([]byte, error) {
  tTime := time.Time(t)
  return []byte(fmt.Sprintf("\"%v\"", tTime.Format("2006-01-02 15:04:05"))), nil
}

func (t LocalTime) Value() (driver.Value, error) {
  // LocalTime 转换成 time.Time 类型
  tTime := time.Time(t)
  return tTime.Format("2006-01-02 15:04:05"), nil
}

func (t *LocalTime) UnmarshalJSON(data []byte) error {
  if string(data) == "null" {
    return nil
  }
  var err error
  //前端接收的时间字符串
  str := string(data)
  //去除接收的str收尾多余的"
  timeStr := strings.Trim(str, "\"")
  t1, err := time.Parse("2006-01-02 15:04:05", timeStr)
  *t = LocalTime(t1)
  return err
}

type StudentLocal struct {
  Id       int
  Name     string
  Age      int
  Sex      string
  CreateAt LocalTime
}

// TableName 指定表名
func (StudentLocal) TableName() string {
  return "student"
}

var db *gorm.DB
var err error

func init() {
  //dsn格式 user:pass@tcp(ip:port)/dbname?charset=utf8mb4&parseTime=True&loc=Local
  dsn := "user:pass@tcp(127.0.0.1:3306)/test?charset=utf8mb4&parseTime=True&loc=Local"
  db, err = gorm.Open(mysql.Open(dsn), &gorm.Config{
    NamingStrategy: schema.NamingStrategy{
      TablePrefix:   "",   // 表前缀
      SingularTable: true, // 禁用表名复数
    }})
  if err != nil {
    panic(err)
  }
}

func main() {
  var student Student
  db.First(&student) // 取第一条到student
  js, _ := json.Marshal(student)
  fmt.Println(string(js))
  // {"Id":1,"Name":"张三","Age":20,"Sex":"男","CreateAt":"2022-12-06T17:49:06+08:00"}

  var studentLocal StudentLocal
  db.First(&studentLocal) // 取第一条到student

  js, _ = json.Marshal(studentLocal)
  fmt.Println(string(js))
  // {"Id":1,"Name":"张三","Age":20,"Sex":"男","CreateAt":"2022-12-06 17:49:06"}

  b, _ := studentLocal.CreateAt.MarshalJSON()
  fmt.Println(string(b))
  // "2022-12-06 17:49:06"

  value, _ := studentLocal.CreateAt.Value()
  fmt.Println(value)
  // 2022-12-06 17:49:06
}