将JSON日期字符串解析为Golang中的BSON日期。

huangapple
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英文:

Unmarshal JSON date string to BSON date in Golang

问题

这应该很简单，但我没有取得太多进展。假设我有一个包含UTC日期的JSON，像这样：

  1. {
  2.   "name": "Lex",
  3.   "dob": "2022-11-01T06:30:30.639326208Z"
  4. }

我想将其插入MongoDB集合。在Go中，我这样做：

  1. import (
  2. 	"go.mongodb.org/mongo-driver/bson"
  3. 	"go.mongodb.org/mongo-driver/mongo"
  4. )
  6. ...
  8. var doc any
  9. // 顺便问一下，第二个参数是做什么的？文档中没有提到
  10. _ = bson.UnmarshalExtJSON(jsonBytes, false, &doc)
  11. mongoCollection.InsertOne(context.TODO(), doc)

插入操作是成功的，但dob字段只是一个字符串。如何正确地将其作为日期插入？我的约束条件是：

  1. 我不能更改输入的JSON。
  2. 我不能手动编写Mongo文档，因为我可能处理的是大型不可预测的对象，而且不知道哪些字段/嵌套字段具有日期字符串。

这可行吗？似乎应该有一条明确的途径来实现这个目标。

英文:

This should be easy but I'm not making much headway. Say I have JSON with a UTC date like this:

  1. {
  2.   "name": "Lex",
  3.   "dob": "2022-11-01T06:30:30.639326208Z"
  4. }

I'd like to insert it in a MongoDB collection. In Go, I do:

  1. import (
  2. 	"go.mongodb.org/mongo-driver/bson"
  3. 	"go.mongodb.org/mongo-driver/mongo"
  4. )
  6. ...
  8. var doc any
  9. // by the way what does the 2nd param do?  docs don't mention it
  10. _ = bson.UnmarshalExtJSON(jsonBytes, false, &doc)
  11. mongoCollection.InsertOne(context.TODO(), doc)

The insert works, but the dob field is just a string. What's the correct way to insert it as Date? My constraints are:

  1. I cannot change the input JSON
  2. I can't manually write the Mongo doc because I could be dealing with large unpredictable objects and won't know which fields/nested fields have a date string

Is this doable? Seems like there has to be a paved road for how to do this.

答案1

得分: 2

你可以定义一个自定义的bsoncodec.ValueDecoder解码器来将日期字符串解码为time.Time，然后通过RegisterTypeDecoder进行注册。

  1. func dateTimeDecodeValue(dc bsoncodec.DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
  2.     ts, _ := vr.ReadString()
  3.     t, err := time.Parse(time.RFC3339Nano, ts)
  4.     if err != nil {
  5.         return err
  6.     }
  8.     val.Set(reflect.ValueOf(t))
  10.     return nil
  11. }
  13. var tDateTime = reflect.TypeOf(time.Time{})
  15. type TestDoc struct {
  16.     Name string    `bson:"name"`
  17.     Dob  time.Time `bson:"dob"`
  18. }
  20. func createCustomRegistry() *bsoncodec.RegistryBuilder {
  21.     var primitiveCodecs bson.PrimitiveCodecs
  23.     rb := bsoncodec.NewRegistryBuilder()
  24.     bsoncodec.DefaultValueEncoders{}.RegisterDefaultEncoders(rb)
  25.     bsoncodec.DefaultValueDecoders{}.RegisterDefaultDecoders(rb)
  26.     rb.RegisterTypeDecoder(tDateTime, bsoncodec.ValueDecoderFunc(dateTimeDecodeValue))
  27.     primitiveCodecs.RegisterPrimitiveCodecs(rb)
  28.     return rb
  29. }

或者将日期字符串解析为BSON日期的示例代码

  1. func dateTimeDecodeValue(dc bsoncodec.DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
  2.     ts, _ := vr.ReadString()
  3.     t, err := time.Parse(time.RFC3339Nano, ts)
  4.     if err != nil {
  5.         val.SetString(ts)
  6.     } else {
  7.         val.Set(reflect.ValueOf(primitive.DateTime(t.UnixMilli())))
  8.     }
  10.     return nil
  11. }
  13. var tDateTime = reflect.TypeOf(primitive.DateTime(0))
  15. type TestDoc struct {
  16.     Name string             `bson:"name"`
  17.     Dob  primitive.DateTime `bson:"dob"`
  18. }
  20. func createCustomRegistry() *bsoncodec.RegistryBuilder {
  21.     var primitiveCodecs bson.PrimitiveCodecs
  23.     rb := bsoncodec.NewRegistryBuilder()
  24.     bsoncodec.DefaultValueEncoders{}.RegisterDefaultEncoders(rb)
  25.     bsoncodec.DefaultValueDecoders{}.RegisterDefaultDecoders(rb)
  26.     rb.RegisterTypeDecoder(tDateTime, bsoncodec.ValueDecoderFunc(dateTimeDecodeValue))
  27.     primitiveCodecs.RegisterPrimitiveCodecs(rb)
  28.     return rb
  29. }

然后通过UnmarshalExtJSONWithRegistry使用这个注册器。

  1. func main() {
  2.     jsonBytes := []byte(`{
  3.        "name": "ben",
  4.        "dob": "2022-11-01T06:30:30.639326208Z"
  5.     }`)
  7.     var customRegistry = createCustomRegistry().Build()
  9.     var doc TestDoc
  10.     _ = bson.UnmarshalExtJSONWithRegistry(customRegistry, jsonBytes, false, &doc)
  11.     fmt.Println(doc)
  12. }

完整代码请参考PLAYGROUND。

关于Canonical参数，请参考文档。

Canonical Extended JSON是基于JSON标准的字符串格式，用于描述BSON文档。Canonical Extended JSON强调类型保留，但牺牲了可读性和互操作性。

英文:

You could define one custom decoders of bsoncodec.ValueDecoder to decode the date string to time.Time, then register it through RegisterTypeDecoder

  1. func dateTimeDecodeValue(dc bsoncodec.DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
  2. 	ts, _ := vr.ReadString()
  3. 	t, err := time.Parse(time.RFC3339Nano, ts)
  4. 	if err != nil {
  5. 		return err
  6. 	} 
  8. 	val.Set(reflect.ValueOf(t))
  10. 	return nil
  11. }
  13. var tDateTime = reflect.TypeOf(time.Time{})
  15. type TestDoc struct {
  16. 	Name string    `bson:"name"`
  17. 	Dob  time.Time `bson:"dob"`
  18. }
  20. func createCustomRegistry() *bsoncodec.RegistryBuilder {
  21. 	var primitiveCodecs bson.PrimitiveCodecs
  23. 	rb := bsoncodec.NewRegistryBuilder()
  24. 	bsoncodec.DefaultValueEncoders{}.RegisterDefaultEncoders(rb)
  25. 	bsoncodec.DefaultValueDecoders{}.RegisterDefaultDecoders(rb)
  26. 	rb.RegisterTypeDecoder(tDateTime, bsoncodec.ValueDecoderFunc(dateTimeDecodeValue))
  27. 	primitiveCodecs.RegisterPrimitiveCodecs(rb)
  28. 	return rb
  29. }

Or to parse date string to BSON date sample codes

  1. func dateTimeDecodeValue(dc bsoncodec.DecodeContext, vr bsonrw.ValueReader, val reflect.Value) error {
  2. 	ts, _ := vr.ReadString()
  3. 	t, err := time.Parse(time.RFC3339Nano, ts)
  4. 	if err != nil {
  5. 		val.SetString(ts)
  6. 	} else {
  7. 		val.Set(reflect.ValueOf(primitive.DateTime(t.UnixMilli())))
  8. 	}
  10. 	return nil
  11. }
  13. var tDateTime = reflect.TypeOf(primitive.DateTime(0))
  15. type TestDoc struct {
  16. 	Name string             `bson:"name"`
  17. 	Dob  primitive.DateTime `bson:"dob"`
  18. }
  20. func createCustomRegistry() *bsoncodec.RegistryBuilder {
  21. 	var primitiveCodecs bson.PrimitiveCodecs
  23. 	rb := bsoncodec.NewRegistryBuilder()
  24. 	bsoncodec.DefaultValueEncoders{}.RegisterDefaultEncoders(rb)
  25. 	bsoncodec.DefaultValueDecoders{}.RegisterDefaultDecoders(rb)
  26. 	rb.RegisterTypeDecoder(tDateTime, bsoncodec.ValueDecoderFunc(dateTimeDecodeValue))
  27. 	primitiveCodecs.RegisterPrimitiveCodecs(rb)
  28. 	return rb
  29. }

Then use this register through UnmarshalExtJSONWithRegistry

  2. func main() {
  3. 	jsonBytes := []byte(`{
  4.        "name": "ben",
  5.        "dob": "2022-11-01T06:30:30.639326208Z"
  6.     }`)
  8. 	var customRegistry = createCustomRegistry().Build()
  10. 	var doc TestDoc
  11. 	_ = bson.UnmarshalExtJSONWithRegistry(customRegistry, jsonBytes, false, &doc)
  12. 	fmt.Println(doc)
  13. }

Full codes
<kbd>PLAYGROUND</kbd>

As for Canonical parameter please refer to doc

> Canonical Extended JSON - A string format based on the JSON standard that describes BSON documents. Canonical Extended JSON emphasizes type preservation at the expense of readability and interoperability.

huangapple
  • 本文由 发表于 2022年11月1日 14:44:25
  • 转载请务必保留本文链接：https://go.coder-hub.com/74272391.html
  • bson
  • go
  • marshalling
  • mongodb
  • unmarshalling
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