JSON marshall可空类型值在数据库/sql Go中

I am trying to figure out how one can properly marhsall nullable type (string, int, time) properly to JSON in Go. I know that database/sql provide sql.NullTime, sql.NullInt, etc but when you marshall these values, you get something like

我想弄清楚如何在Go中正确地将所有可空类型(string, int, time)映射为JSON。我知道数据库/sql提供sql。NullTime,sql。NullInt，等等但是当你调整这些值时，你会得到类似的结果

{"first_name": {
  "Value": "",
  "Valid": false,
}}

What I really want is

我真正想要的是

{"first_name": null}

I understand that you can implement your own MarshalJSON to do this (I wrote about it here http://dennissuratna.com/marshalling-nullable-string-db-value-to-json-in-go/)

我理解您可以实现自己的MarshalJSON来实现这一点(我在http://dennissuratna.com/marshalling-nullable-string-db-value-to-json-in-go/中对此进行了介绍)

BUT I am wondering if anyone knows a better way to do this. I want to know other people know a less tedious way to do this.

但我想知道是否有人知道更好的方法。我想知道其他人知道一个不那么乏味的方法。

3 个解决方案

#1

Create a type that embeds (e.g.) sql.NullInt and implements the json.Marshaler interface.

创建嵌入(例如)sql的类型。空出并实现json。封送拆收器接口。

#2

May be late, but when searching for the same problem google report this page at a high rank, so : my solution is to define special type that surcharge NullInt64 for exemple and has and export JSON

可能会很晚，但是当搜索相同的问题时谷歌会以较高的级别报告这个页面，所以:我的解决方案是定义一个特殊类型，例如，附加NullInt64并拥有和导出JSON

Example for NullInt64 :

NullInt64的例子:

// NullInt64 is the same as sql.NullInt64
// But when exported to JSON it is null or the int64 val that is exported
// not a JSON containing Value and Valid properties
type NullInt64 struct {
    sql.NullInt64
}

// NullInt64 MarshalJSON interface redefinition
func (r NullInt64) MarshalJSON() ([]byte, error) {
    if r.Valid {
        return json.Marshal(r.Int64)
    } else {
        return json.Marshal(nil)
    }
}

And then replace all sql.NullInt64 by NullInt64. You can easily do the same for sql.NullString. Hope it helps

然后替换所有sql。NullInt64 NullInt64。对于sql.NullString，您可以轻松地执行相同的操作。希望它能帮助

#3

If you really want to have null field, you will have to resort to a custom marshaller (or maybe, just maybe, use *string fields in struct and assign nil instead of an empty string).

如果您真的想要有一个空字段，那么您将不得不使用自定义的marshaller(或者，也许，只是可能，在struct中使用*string字段，并指定nil而不是空字符串)。

However, if you look at the original goal of JSON (JavaScript Object Notation), you will notice that in JavaScript there is hardly any difference between:

但是，如果您查看JSON的最初目标(JavaScript对象表示法)，您会注意到在JavaScript中几乎没有什么区别:

var obj = JSON.parse('{"first_name": null }');
alert(obj.first_name)

and:

和:

var obj = JSON.parse('{}');
alert(obj.first_name)

In other words: assigning null to a field has the same effect as not specifying it all. And most JSON parsers work like this.

换句话说:将null赋值给字段的效果与未指定所有字段的效果相同。大多数JSON解析器是这样工作的。

Not specifying empty fields is supported by the Go JSON marshaller:

Go JSON编组器支持不指定空字段:

type MyType struct {
    firstname string `json:omitempty`
}

In the end, it depends on what you want to do with your JSON :)

最后，这取决于您想要如何处理JSON:)

#1