Play Framework 2.2.2 Scala JSON读取带有未定义/空元素，导致NoSuchElementException [英] Play Framework 2.2.2 Scala JSON reads with undefined/null elements causing NoSuchElementException

问题描述

给出以下JSON数组:

Given the following JSON array:

{
    "success": true,
    "data": [
        {
            "id": 600,
            "stage_id": 15,
            "title": "test deal",
            "value": 0,
            "currency": "EUR",
            "rotten_time": "2014-03-18 17:45:51",
        },
        {
            "id": 601,
            "stage_id": 15,
            "title": "test deal2 deal",
            "value": 0,
            "currency": "EUR",
            "rotten_time": "2014-03-24 14:11:00"
        },
        {
            "id": 602,
            "stage_id": 15,
            "title": "test deal2 deal",
            "value": 0,
            "currency": "EUR",
            "rotten_time": null
        }
    ],
    "additional_data": {
        "pagination": {
            "start": 0,
            "limit": 100,
            "more_items_in_collection": false
        }
    }
}

使用reads方法实例化如下对象

Using the reads method to instanciate objects like below

case class Deal(id: Long, stage_id: Long, status: String, rotten_time: Date)

implicit val dealReader = Json.reads[Deal]

val futureJson: Future[List[Deal]] = futureResponse.map(
  response => (response.json \ "data").validate[List[Deal]].get
)

当元素的值为null时，我会收到NoSuchElementsException(就像rotten_time一样)

I get a NoSuchElementsException when an element's value is null (like for rotten_time)

我想得到这样的东西

> println(deals.toString)
> Deal(601,15,open,Mon Mar 18 17:45:51 CET 2014)
> Deal(602,15,open,Mon Mar 18 14:11:00 CET 2014)
> Deal(603,15,open,null)

即使字段值为NULL，有没有办法确保对象实例化?我认为没有理由为每个现有字段都分配一个值.

Is there a way to ensure object instanciation even if a field value is NULL? I see no reason why every existing field has to be assigned a value to.

我在此处和

I found related questions here and here but they did not help me to solve my problem.

推荐答案

我自己找到了答案.我是Scala的新手，所以对我来说并不明显.将字段类型更改为Option [Date]解决了该问题.

I found the answer myself. I am new to Scala so it wasn't obvious for me. Changing the field type to Option[Date] solved the problem.

case class Deal(id: Long, stage_id: Long, status: String, rotten_time: Option[Date])

所以结果是

> println(deals.toString)
> Deal(601,15,open,Some(Mon Mar 18 17:45:51 CET 2014))
> Deal(602,15,open,Some(Mon Mar 18 14:11:00 CET 2014))
> Deal(603,15,open,None)

这有点意外，因为据说Option []是围绕NullPointerException s而不是NoSuchElementException s的一种方式.

This is a little bit unexpected as Option[] is said to be a way around NullPointerExceptions but not NoSuchElementExceptions.

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