JSON omitempty 与 time.Time 字段

使用Golang编程语言开发Web应用程序时，我们经常需要处理JSON数据。在处理JSON数据时，有时我们希望在生成的JSON中忽略掉一些字段，即这些字段为空时不会被包含在JSON中。为了实现这个功能，我们可以使用Golang的JSON标签`omitempty`。

go
type Person struct {
    Name   string `json:"name,omitempty"`
    Age    int    `json:"age,omitempty"`
    Address string `json:"address,omitempty"`
}

go
type Event struct {
    Name string    `json:"name"`
    Time time.Time `json:"time"`
}
func (e Event) MarshalJSON() ([]byte, error) {
    type Alias Event
    return json.Marshal(&struct {
        Time string `json:"time"`
        *Alias
    }{
        Time: e.Time.Format("2006-01-02 15:04:05"),
        Alias: (*Alias)(&e),
    })
}

go
type Person struct {
    Name    string `json:"name,omitempty"`
    Age     int    `json:"age,omitempty"`
    Address string `json:"address,omitempty"`
}
func main() {
    person1 := Person{Name: "Alice", Age: 25, Address: "123 Main St"}
    person2 := Person{Name: "Bob"}
    json1, _ := json.Marshal(person1)
    json2, _ := json.Marshal(person2)
    fmt.Println(string(json1))  // 输出: {"name":"Alice","age":25,"address":"123 Main St"}
    fmt.Println(string(json2))  // 输出: {"name":"Bob"}
}

go
type Event struct {
    Name string    `json:"name"`
    Time time.Time `json:"time"`
}
func (e Event) MarshalJSON() ([]byte, error) {
    type Alias Event
    return json.Marshal(&struct {
        Time string `json:"time"`
        *Alias
    }{
        Time: e.Time.Format("2006-01-02 15:04:05"),
        Alias: (*Alias)(&e),
    })
}
func main() {
    event := Event{Name: "Meeting", Time: time.Now()}
    json, _ := json.Marshal(event)
    fmt.Println(string(json))  // 输出: {"name":"Meeting","time":"2022-01-01 12:00:00"}
}