使用 Go 将内容以 UUID 类型保存到 Mongo 数据库的方法

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通过 mongodb 控制台我可以添加文档：

{
        "_id": objectid(),
        "name": "john",
        "sign": uuid("32e79135-76c4-4682-80b2-8c813be9b792")
}

接下来我可以阅读它：

{
    _id: objectid('64d4ce25ac7c4327e76a53e3'),
    name: "john",
    sign: uuid("32e7913576c4468280b28c813be9b792")
}

我能做到： db.getcollection('people').find({"sign": uuid("32e79135-76c4-4682-80b2-8c813be9b792")})

我可以找到人。

但是当我在 go 中尝试时：

package main

import (
    "context"
    "fmt"
    "log"

    "github.com/google/uuid"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

type Person struct {
    Name string    `bson:"name"`
    Sign uuid.UUID `bson:"sign"`
}

func main() {
    client, err := mongo.Connect(context.Background(), options.Client().ApplyURI("mongodb://localhost:27017"))
    if err != nil {
        log.Fatal(err)
    }
    defer client.Disconnect(context.Background())

    db := client.Database("mydatabase")
    collection := db.Collection("people")

    signUUID := uuid.New()

    person := Person{
        Name: "John",
        Sign: signUUID,
    }

    _, err = collection.InsertOne(context.Background(), person)
    if err != nil {
        log.Fatal(err)
    }

    fmt.Println("Document inserted successfully")
}

然后在 mongo 我有：

{ _id: objectid('64d4cf0a308251580cffee4e'), 姓名: 'john', 符号: bindata(0, 'wqax6oylt1eureehicik9q==') }

我想要一个 uuid 类型的“sign”字段，并且能够在 mongo 中轻松搜索它。

正确答案

包 github.com/google/uuid 没有实现 bson.ValueMarshaler 接口来将自身编组为 mongodb uuid，这就是它不起作用的原因。

我们可以注册自己的编解码器，将其编码为 mongodb uuid 或从 mongodb uuid 解码。请参阅下面的演示：

package main

import (
    "context"
    "fmt"
    "log"
    "reflect"

    "github.com/google/uuid"
    "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/bson/bsoncodec"
    "go.mongodb.org/mongo-driver/bson/bsonrw"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
)

type person struct {
    name string    `bson:"name"`
    sign uuid.uuid `bson:"sign"`
}

func main() {
    tuuid := reflect.typeof(uuid.nil)
    bson.defaultregistry.registertypeencoder(tuuid, bsoncodec.valueencoderfunc(func(ec bsoncodec.encodecontext, vw bsonrw.valuewriter, val reflect.value) error {
        // borrowed from https://github.com/mongodb/mongo-go-driver/blob/89c7e1d1d9a2954472fe852baf27ecca9dbf9bbf/bson/bsoncodec/default_value_encoders.go#l684-l691
        if !val.isvalid() || val.type() != tuuid {
            return bsoncodec.valueencodererror{name: "uuidencodevalue", types: []reflect.type{tuuid}, received: val}
        }
        uuid := val.interface().(uuid.uuid)

        return vw.writebinarywithsubtype(uuid[:], bson.typebinaryuuid)
    }))
    bson.defaultregistry.registertypedecoder(tuuid, bsoncodec.valuedecoderfunc(func(dc bsoncodec.decodecontext, vr bsonrw.valuereader, val reflect.value) error {
        // borrowed from https://github.com/mongodb/mongo-go-driver/blob/89c7e1d1d9a2954472fe852baf27ecca9dbf9bbf/bson/bsoncodec/default_value_decoders.go#l694-l706
        if !val.canset() || val.type() != tuuid {
            return bsoncodec.valuedecodererror{name: "uuiddecodevalue", types: []reflect.type{tuuid}, received: val}
        }

        var data []byte
        var subtype byte
        var err error
        switch vrtype := vr.type(); vrtype {
        case bson.typebinary:
            data, subtype, err = vr.readbinary()
        case bson.typenull:
            err = vr.readnull()
        case bson.typeundefined:
            err = vr.readundefined()
        default:
            err = fmt.errorf("cannot decode %v into a binary", vrtype)
        }

        if err != nil {
            return err
        }

        if subtype != bson.typebinaryuuid {
            return fmt.errorf("cannot decode subtype %v into a uuid", subtype)
        }

        val.set(reflect.valueof(uuid.uuid(data)))
        return nil
    }))

    client, err := mongo.connect(context.background(), options.client().applyuri("mongodb://localhost:27017"))
    if err != nil {
        log.fatal(err)
    }
    defer client.disconnect(context.background())

    db := client.database("mydatabase")
    collection := db.collection("people")

    signuuid := uuid.new()

    person := person{
        name: "john",
        sign: signuuid,
    }

    if _, err = collection.insertone(context.background(), person); err != nil {
        log.fatal(err)
    }

    var p person

    if err := collection.findone(context.background(),
        bson.m{"sign": signuuid},
    ).decode(&p); err != nil {
        log.fatal(err)
    }
    log.printf("%+v\n", p)
}

请参阅此处的讨论：Add support for mongodb UUID type。

为了完整起见，下面显示了实现 bson.valuemarshaler 和 bson.valueunmarshaler 接口的方法：

package main

import (
    "context"
    "errors"
    "fmt"
    "log"

    "github.com/google/uuid"
    "go.mongodb.org/mongo-driver/bson"
    "go.mongodb.org/mongo-driver/bson/bsontype"
    "go.mongodb.org/mongo-driver/mongo"
    "go.mongodb.org/mongo-driver/mongo/options"
    "go.mongodb.org/mongo-driver/x/bsonx/bsoncore"
)

type myUUID struct {
    uuid.UUID
}

var (
    _ bson.ValueMarshaler   = (*myUUID)(nil)
    _ bson.ValueUnmarshaler = (*myUUID)(nil)
)

func (u myUUID) MarshalBSONValue() (bsontype.Type, []byte, error) {
    return bson.TypeBinary, bsoncore.AppendBinary(nil, bson.TypeBinaryUUID, []byte(u.UUID[:])), nil
}

func (u *myUUID) UnmarshalBSONValue(typ bsontype.Type, value []byte) error {
    if typ != bson.TypeBinary {
        return fmt.Errorf("cannot unmarshal %v into a Binary", typ)
    }
    subtype, bin, rem, ok := bsoncore.ReadBinary(value)
    if subtype != bson.TypeBinaryUUID {
        return fmt.Errorf("cannot unmarshal binary subtype %v into a UUID", subtype)
    }
    if len(rem) > 0 {
        return fmt.Errorf("value has extra data: %v", rem)
    }
    if !ok {
        return errors.New("value does not have enough bytes")
    }
    *u = myUUID{UUID: uuid.UUID(bin)}
    return nil
}

type Person struct {
    Name string `bson:"name"`
    Sign myUUID `bson:"sign"`
}

func main() {
    client, err := mongo.Connect(context.Background(), options.Client().ApplyURI("mongodb://localhost:27017"))
    if err != nil {
        log.Fatal(err)
    }
    defer client.Disconnect(context.Background())

    db := client.Database("mydatabase")
    collection := db.Collection("people")

    signUUID := myUUID{UUID: uuid.New()}

    person := Person{
        Name: "John",
        Sign: signUUID,
    }

    if _, err = collection.InsertOne(context.Background(), person); err != nil {
        log.Fatal(err)
    }

    var p Person

    if err := collection.FindOne(context.Background(),
        bson.M{"sign": signUUID},
    ).Decode(&p); err != nil {
        log.Fatal(err)
    }
    log.Printf("%+v\n", p)
}

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