我正在尝试编写一个查询,以使用Casbah通过对象ID查找,这似乎很简单,但是...我找不到。

我尝试了这个:

def get(id: Option[String]): User = {
    val mongoDB : MongoDB = MongoConnection().apply("test")
    val mongoColl : MongoCollection = mongoDB.apply("users")
    val objectId = id.getOrElse().asInstanceOf[String]
    val o : DBObject = MongoDBObject("_id" -> objectId)
    val u = mongoColl.findOne(o)
    val user = new User()
    for(x <- u){
         user.id = x.getAs[String]("_id")
         user.username = x.getAs[String]("username")
         user.password = x.getAs[String]("password")
    }
    user
}


还有这个:

def get(id: Option[String]): User = {
        val mongoDB : MongoDB = MongoConnection().apply("test")
        val mongoColl : MongoCollection = mongoDB.apply("users")
        val objectId = "ObjectId(\"" +id.getOrElse().asInstanceOf[String] + "\")"
        val o : DBObject = MongoDBObject("_id" -> objectId)
        val u = mongoColl.findOne(o)
        val user = new User()
        for(x <- u){
             user.id = x.getAs[String]("_id")
             user.username = x.getAs[String]("username")
             user.password = x.getAs[String]("password")
        }
        user
    }


编译并运行,但没有结果。
我也尝试过这个:

def get(id: Option[String]): User = {
    val mongoDB : MongoDB = MongoConnection().apply("test")
    val mongoColl : MongoCollection = mongoDB.apply("users")
    val objectId : ObjectId = id.getOrElse().asInstanceOf[ObjectId]
    val o : DBObject = MongoDBObject("_id" -> objectId)
    val u = mongoColl.findOne(o)
    val user = new User()
    for(x <- u){
         user.id = x.getAs[String]("_id")
         user.username = x.getAs[String]("username")
         user.password = x.getAs[String]("password")
    }
    user
}


但是,由于String无法转换为ObjectId,因此无法编译。

java.lang.ClassCastException: java.lang.String cannot be cast to org.bson.types.ObjectId


谢谢您的帮助 :)

最佳答案

“ _id”通常作为对象ID存储在MongoDB中,而不是字符串中存储。字符串和对象ID是不同的类型,您不能将字符串转换为对象ID。 ObjectId在MongoDB中也是一个独特的类型,因此ObjectId(“ abcdefgh123”)与字符串“ abcdefgh123”不同。

您需要在Casbah中按ObjectID搜索。尝试以下方法:

def get(id: Option[ObjectId]): User = {
    val mongoDB : MongoDB = MongoConnection().apply("test")
    val mongoColl : MongoCollection = mongoDB.apply("users")
    val objectId : ObjectId = id.getOrElse().asInstanceOf[ObjectId]
    id.foreach( oid => {
      val o : DBObject = MongoDBObject("_id" -> oid)
      val u = mongoColl.findOne(o)
      val user = new User()
      for(x <- u){
        user.id = x.getAs[ObjectId]("_id")
        user.username = x.getAs[String]("username")
        user.password = x.getAs[String]("password")
      }
      user
    })
  }

09-17 04:35