[英]How to list unknown fields after json parsing
假設我們有以下Go結構:
type Config struct {
Name string `json:"name,omitempty"`
Params []Param `json:"params,omitempty"`
}
type Param struct {
Name string `json:"name,omitempty"`
Value string `json:"value,omitempty"`
}
並跟隨json:
{
"name": "parabolic",
"subdir": "pb",
"params": [{
"name": "input",
"value": "in.csv"
}, {
"name": "output",
"value": "out.csv",
"tune": "fine"
}]
}
我們會進行編組:
cfg := Config{}
if err := json.Unmarshal([]byte(cfgString), &cfg); err != nil {
log.Fatalf("Error unmarshalling json: %v", err)
}
fmt.Println(cfg)
https://play.golang.org/p/HZgo0jxbQrp
輸出將是{parabolic [{input in.csv} {output out.csv}]}
,這很有意義-未知字段將被忽略。
問題:如何找出哪些字段被忽略?
即getIgnoredFields(cfg, cfgString)
將返回["subdir", "params[1].tune"]
(有一個DisallowUnknownFields
選項,但有所不同:此選項將導致Unmarshal
錯誤,而問題是如何仍然解析JSON而不會出現錯誤,並找出哪些字段被忽略了)
不知道這是否是最好的方法,但是我所做的是:
如果當前級別類型是map:
如果當前級別類型為數組:
碼:
// ValidateUnknownFields checks that provided json
// matches provided struct. If that is not the case
// list of unknown fields is returned.
func ValidateUnknownFields(jsn []byte, strct interface{}) ([]string, error) {
var obj interface{}
err := json.Unmarshal(jsn, &obj)
if err != nil {
return nil, fmt.Errorf("error while unmarshaling json: %v", err)
}
return checkUnknownFields("", obj, reflect.ValueOf(strct)), nil
}
func checkUnknownFields(keyPref string, jsn interface{}, strct reflect.Value) []string {
var uf []string
switch concreteVal := jsn.(type) {
case map[string]interface{}:
// Iterate over map and check every value
for field, val := range concreteVal {
fullKey := fmt.Sprintf("%s.%s", keyPref, field)
subStrct := getSubStruct(field, strct)
if !subStrct.IsValid() {
uf = append(uf, fullKey[1:])
} else {
subUf := checkUnknownFields(fullKey, val, subStrct)
uf = append(uf, subUf...)
}
}
case []interface{}:
for i, val := range concreteVal {
fullKey := fmt.Sprintf("%s[%v]", keyPref, i)
subStrct := strct.Index(i)
uf = append(uf, checkUnknownFields(fullKey, val, subStrct)...)
}
}
return uf
}
完整版本: https : //github.com/yb172/json-unknown/blob/master/validator.go
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