golang map转json的顺序问题
json
适用于现代 C++ 的 JSON。
项目地址:https://gitcode.com/gh_mirrors/js/json

·
我们都知道map是无序的,每次取出key/value的顺序都可能不一致,但map转json的顺序是不是也是无序的吗?尽管json中的参数顺序大部分情况下对使用没有影响,我们不妨看看源码中怎么处理的。
先说结论:
map转json是有序的,按照ASCII码升序排列key。
溯源
源码位于encoding/json/encode.go中
type mapEncoder struct {
elemEnc encoderFunc
}
func (me mapEncoder) encode(e *encodeState, v reflect.Value, opts encOpts) {
if v.IsNil() {//为nil时,返回null
e.WriteString("null")
return
}
e.WriteByte('{')
// Extract and sort the keys.
keys := v.MapKeys()//获取map中的所有keys
sv := make([]reflectWithString, len(keys))
for i, v := range keys {
sv[i].v = v
if err := sv[i].resolve(); err != nil {//处理key,尤其是非string(int/uint)类型的key转string
e.error(&MarshalerError{v.Type(), err})
}
}
//排序,升序,直接比较字符串
sort.Slice(sv, func(i, j int) bool { return sv[i].s < sv[j].s })
for i, kv := range sv {
if i > 0 {
e.WriteByte(',')
}
e.string(kv.s, opts.escapeHTML)
e.WriteByte(':')
me.elemEnc(e, v.MapIndex(kv.v), opts)
}
e.WriteByte('}')
}
func newMapEncoder(t reflect.Type) encoderFunc {
switch t.Key().Kind() {
case reflect.String,
reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64,
reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
default:
if !t.Key().Implements(textMarshalerType) {
return unsupportedTypeEncoder
}
}
me := mapEncoder{typeEncoder(t.Elem())}
return me.encode
}




适用于现代 C++ 的 JSON。
最近提交(Master分支:4 个月前 )
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---------
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