玩！ framework 2.0 scala-ClassCastException:无法将models.MyModel强制转换为models.MyModel [英] Play! framework 2.0 scala - ClassCastException: models.MyModel cannot be cast to models.MyModel

问题描述

这是我的第一个play 2.0应用程序，scala对我来说仍然很新，因此我可能在某个地方犯了一个错误.我正在使用捆绑了Salat和Casbah的全新插件: https://github.com/leon/play -salat

This is my first play 2.0 app, and scala is still pretty new to me, so I'm likely making a mistake somewhere. I'm using a pretty new plugin that bundles Salat and Casbah: https://github.com/leon/play-salat

我已经简化并重命名了所有内容以使其通用.

I've simplified and renamed everything to make it generic.

我的视图(views/MyController/search.scala.html):

@(modelList:List[models.MyModel])
@main(title = "Search MyModel") {
  <table>
  @for(a <- modelList) {
    <tr><td>@a.field<td>@a.field2</li>
  } 
  </table>
}

我的控制器(controllers/MyController.scala):

package controllers

import play.api._
import play.api.mvc._
import play.api.data._
import play.api.data.Forms._
import com.mongodb.casbah.Imports._
import models._

object MyController extends Controller {
  def search = Action {
    val modelList = MyModel.all.toList;
    Ok(views.html.MyController.search(modelList))
  }
}

我的模特:(models/MyModel.scala):

package models

import play.api.Play.current
import java.util.{Date}
import com.novus.salat._
import com.mongodb.casbah.Imports._
import se.radley.plugin.mongodb._
import se.radley.plugin.mongodb.salat._

case class MyModel(
  id: ObjectId = new ObjectId,
  field: String,
  field2: String
)

object MyModel extends SalatDAO[MyModel, ObjectId](collection = getCollection("mycollection")) {
  def all = find(MongoDBObject())
}

我收到此错误:

ClassCastException: models.MyModel cannot be cast to models.MyModel

对我来说没有什么意义-有人遇到过这种情况吗?

Which doesn't make much sense to me--has anyone run into something like this?

完整堆栈跟踪:

play.core.ActionInvoker$$anonfun$receive$1$$anon$1: Execution exception [[ClassCastException: models.MyModel cannot be cast to models.MyModel]]
at play.core.ActionInvoker$$anonfun$receive$1.apply(Invoker.scala:82) [play_2.9.1.jar:2.0]
at play.core.ActionInvoker$$anonfun$receive$1.apply(Invoker.scala:63) [play_2.9.1.jar:2.0]
at akka.actor.Actor$class.apply(Actor.scala:290) [akka-actor.jar:2.0]
at play.core.ActionInvoker.apply(Invoker.scala:61) [play_2.9.1.jar:2.0]
at akka.actor.ActorCell.invoke(ActorCell.scala:617) [akka-actor.jar:2.0]
at akka.dispatch.Mailbox.processMailbox(Mailbox.scala:179) [akka-actor.jar:2.0]
Caused by: java.lang.ClassCastException: models.MyModel cannot be cast to models.MyModel
at views.html.MyController.search$$anonfun$apply$1.apply(search.template.scala:25) ~[classes/:na]
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:194) ~[scala-library.jar:0.11.2]
at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:194) ~[scala-library.jar:0.11.2]
at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59) ~[scala-library.jar:0.11.2]
at scala.collection.immutable.List.foreach(List.scala:45) ~[scala-library.jar:0.11.2]
at scala.collection.TraversableLike$class.map(TraversableLike.scala:194) ~[scala-library.jar:0.11.2]

推荐答案

我认为这里的问题是您的MyModel集合对象

I think the problem here is that your MyModel collection object

object MyModel extends SalatDAO[MyModel, ObjectId](collection = getCollection("mycollection")) {
  def all = find(MongoDBObject())
}

是您模板中要导入的内容.

Is what is being imported in your template.

我会尝试以下操作:

package models

import play.api.Play.current
import java.util.{Date}
import com.novus.salat._
import com.mongodb.casbah.Imports._
import se.radley.plugin.mongodb._
import se.radley.plugin.mongodb.salat._

case class MyModel(
  id: ObjectId = new ObjectId,
  field: String,
  field2: String
)

object MyModelDAO extends SalatDAO[MyModel, ObjectId](collection = getCollection("mycollection")) {
  def all = find(MongoDBObject())
}

案例类已经随同对象一起提供.在这种情况下，scala会为您生成一个MyModel伴随类.扩展了正确键入的SalatDAO的对象也称为MyModel.您必须查看为case类和MyModel extends SalatDAO[MyModel, ObjectId]类生成的字节码，以查明生成的类名称是什么，我想对于您的case类，其为models.MyObject$.但是，如果您使用不同的名称，那么您应该得到想要的结果.

Case classes already come with companion objects. In this case a MyModel companion class is generated by scala for you. The object extending the properly typed SalatDAO is also named MyModel. You would have to look at the bytecode generated for the case class and the MyModel extends SalatDAO[MyModel, ObjectId] classes to find out what the generated class name is, I think it would be models.MyObject$ for your case class. But if you name it differently, then you should get the result you are looking for.

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