[英]What's the best way to maintain un-parsed JSON fields in Go?
I'd like to decode a JSON blob into a Go struct, manipulate on it, and encode it back to JSON. 我想将JSON blob解码为Go结构,对其进行操作,然后将其编码回JSON。 However, there are dynamic fields in the JSON that aren't relevant to my struct and I want to maintain them when I serialize back to JSON.
但是,JSON中的动态字段与我的struct无关,我想在序列化回JSON时维护它们。
For example: 例如:
{ "name": "Joe Smith",
"age": 42,
"phone": "614-555-1212",
"debug": True,
"codeword": "wolf" }
type Person struct {
Name string
Age uint
Phone string
}
var p Person
json.Unmarshal(data, &p)
// Happy birthday
p.Age++
data, _ = json.Marshal(p)
// Any way to maintain the "debug" and "codeword" fields -- which might not
// be known ahead of time?
I know one possibility is to decode everything into a map[string]interface{}
but boy, do things get ugly when you do that. 我知道一种可能性是将所有内容解码为
map[string]interface{}
但是男孩,当你这样做时,事情变得丑陋。
Is there any way to have the best of both worlds? 有没有办法让两全其美?
With encoding/json
there's no way to do decode a struct and save unknown fields at the same level for posterior re-encoding. 使用
encoding/json
,无法对结构进行解码并将同一级别的未知字段保存为后重新编码。 What you can do is choose not to decode part of the struct by using the json.RawMessage type, along the lines of: 你可以做的是选择不使用json.RawMessage类型解码部分结构, 类似于 :
type Person struct {
Name string
Address json.RawMessage
}
You might workaround that by implementing your own Unmarshaler that decodes the document into a map and saves the unknown keys in a field of the struct, and then have a counterpart Marshaler that puts the fields back before marshaling. 您可以通过实现自己的Unmarshaler解决方法,将文档解码为地图并将未知密钥保存在结构的字段中,然后让对应的Marshaler在编组之前将字段放回。
Just out of curiosity, the feature you're looking for does exist in labix.org/v2/mgo/bson , via the inline tag flag , and the goal was to solve precisely the use case you're describing. 出于好奇,您正在寻找的功能确实存在于labix.org/v2/mgo/bson中 ,通过内联标记标记 ,目标是精确地解决您正在描述的用例。
Turns out I wrote my own library to do this: https://github.com/joeshaw/json-lossless 结果我写了自己的库来做到这一点: https : //github.com/joeshaw/json-lossless
It builds on top of go-simplejson , keeping the parsed JSON state in a simplejson.Json
and proxying state between it and the struct whenever the struct is marshaled or unmarshaled. 它构建在go-simplejson之上,只要结构被封送或解组,就将解析后的JSON状态保持在
simplejson.Json
和它与struct之间的代理状态。
Example usage: 用法示例:
package main
import (
"encoding/json"
"fmt"
"time"
"github.com/joeshaw/json-lossless"
)
type Person struct {
lossless.JSON `json:"-"`
Name string `json:"name"`
Age int `json:"age"`
Birthdate time.Time `json:"birthdate"`
}
func (p *Person) UnmarshalJSON(data []byte) error {
return p.JSON.UnmarshalJSON(p, data)
}
func (p Person) MarshalJSON() []byte, error) {
return p.JSON.MarshalJSON(p)
}
var jsondata = []byte(`
{"name": "David Von Wolf",
"age": 33,
"birthdate": "1980-09-16T10:44:40.295451647-04:00",
"phone": "614-555-1212"}
`)
func main() {
var p Person
err := json.Unmarshal(jsondata, &p)
if err != nil {
panic(err)
}
// Set values on the struct
p.Age++
// Set arbitrary keys not in the struct
p.Set("title", "Chief Wolf")
fmt.Printf("%#v\n", p)
data, err := json.Marshal(p)
if err != nil {
panic(err)
}
fmt.Println(string(data))
}
Prints (formatted for readability by me): 打印(格式化以供我阅读):
main.Person{JSON:lossless.JSON{json:(*simplejson.Json)(0x21020a190)},
Name:"David Von Wolf",
Age:34,
Birthdate:time.Time{sec:62473560280,
nsec:295451647,
loc:(*time.Location)(0x16de60)}}
{"age":34,
"birthdate":"1980-09-16T10:44:40.295451647-04:00",
"name":"David Von Wolf",
"phone":"614-555-1212",
"title": "Chief Wolf"}
包go-simplejson
对于这类工作来说非常方便。
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