mongodb - 从 MongoDBList 中提取数据

Question

我怎样才能从中得到List(String)一个MongoDBList？

val a: MongoDBList = ... // equal to [ { "id" : "0001"} , { "id" : "0017"}]

期望的结果：List("0001", "0017")

Answer 1

MongoDBList扩展了scala.collection.mutable.LinearSeq所以你应该能够使用 toList

val bld = MongoDBList.newBuilder

bld += MongoDBObject("id" -> "0001")
bld += MongoDBObject("id" -> "0017")

val a = bld.result

val l = for( o <- a.toList )
  yield JSON.parse(o.toString).asInstanceOf[DBObject].get("id")

println(l)

//output
//List(0001, 0017)

Answer 2

我会比较喜欢：

val bld = MongoDBList.newBuilder

bld += MongoDBObject("id" -> "0001")
bld += MongoDBObject("id" -> "0017")

val a = bld.result

a.map(x=> x.asInstanceOf[DBObject].getAs[String]("id").get)
// or to avoid nonexitence emelents
a.flatMap(x=> x.asInstanceOf[DBObject].getAs[String]("id"))

我不喜欢这里的 asInstanceOf 如果你有

{ "data" : [ { "id" : "0001"} , { "id" : "0017"}] }

casbash 可以为你序列化 Seq

val a2 = MongoDBObject( "data" -> a )
a2.getAs[Seq[DBObject]]("aa").get.map { x => x.getAs[String]("id").get}