dongming8867
2019-06-18 09:35
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如何使用mongo-go-driver有效地将bson转换为json?

I want to convert bson in mongo-go-driver to json effectively.

I should take care to handle NaN, because json.Marshal fail if NaN exists in data.

For instance, I want to convert below bson data to json.

b, _ := bson.Marshal(bson.M{"a": []interface{}{math.NaN(), 0, 1}})
// How to convert b to json?

The below fails.

// decode
var decodedBson bson.M
bson.Unmarshal(b, &decodedBson)
_, err := json.Marshal(decodedBson)
if err != nil {
    panic(err) // it will be invoked
    // panic: json: unsupported value: NaN
}
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1条回答 默认 最新

  • dtmtu02882 2019-06-18 10:21
    已采纳

    If you know the structure if your BSON, you can create a custom type that implements the json.Marshaler and json.Unmarshaler interfaces, and handles NaN as you wish. Example:

    type maybeNaN struct{
        isNan  bool
        number float64
    }
    
    func (n maybeNaN) MarshalJSON() ([]byte, error) {
        if n.isNan {
            return []byte("null"), nil // Or whatever you want here
        }
        return json.Marshal(n.number)
    }
    
    func (n *maybeNan) UnmarshalJSON(p []byte) error {
        if string(p) == "NaN" {
            n.isNan = true
            return nil
        }
        return json.Unmarshal(p, &n.number)
    }
    
    type myStruct struct {
        someNumber maybeNaN `json:"someNumber" bson:"someNumber"`
        /* ... */
    }
    

    If you have an arbitrary structure of your BSON, your only option is to traverse the structure, using reflection, and convert any occurrences of NaN into a type (possibly a custom type as described above)

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