如何在Java/scala中使用inc运算符创建Decimal128字段 [英] How to create Decimal128 field with inc operator in java/scala

问题描述

我具有以下文档结构:

{
    "moneys": {
      "someKey": NumberDecimal(99)
      ...
      "someOtherRandomKey": NumberDecimal(99)
    }
{

我想要的:当不存在的字段递增时，使用 NumberDecimal值.

What I want: When nonexistent field increments, create that field with NumberDecimal value.

我使用scala驱动程序尝试了此操作，但无法做到这一点:

I tried it with scala driver but cant do that:

//not compiles
collection.findOneAndUpdate(filters,Updates.inc("someOtherKey", new Decimal128(50)))

因为Updates.inc(k,v)需要Number； Decimal128不是Number

我认为问题不在于驱动程序，而在于我的逻辑.

I think problem not in driver, but with my logic.

如何使用scala/java驱动程序实现我的案例?

How can I implement my case with scala/java driver?

推荐答案

通过为scala.math.BigDecimal实现编解码器解决的问题:

Problem solved by implementing codec for scala.math.BigDecimal:

class BigDecimalScalaCodec extends Codec[scala.math.BigDecimal] {

  override def encode(writer: BsonWriter, value: scala.math.BigDecimal, encoderContext: EncoderContext): Unit = {
    writer.writeDecimal128(new Decimal128(value.bigDecimal))
  }

  override def getEncoderClass: Class[scala.math.BigDecimal] = classOf[scala.math.BigDecimal]

  override def decode(reader: BsonReader, decoderContext: DecoderContext): scala.math.BigDecimal = {
    reader.readDecimal128().bigDecimalValue()
  }
}

注册mongo:

 val codecRegistry = fromRegistries(fromCodecs(new BigDecimalScalaCodec()), DEFAULT_CODEC_REGISTRY)

 val database: MongoDatabase = mongoClient.getDatabase("dbName")
    .withCodecRegistry(codecRegistry)

现在我们可以使用scala.math.BigDecimal:

collection.findOneAndUpdate(filters,Updates.inc("someOtherKey", BigDecimal(99))

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