[json4s]:提取不同对象的数组 [英] [json4s]:Extracting Array of different objects
问题描述
我正在使用facebook graph API,响应看起来与此类似:
I am using the facebook graph API and the responses look similar to this:
{
"data": [
{
"id": "311620272349920_311718615673419",
"from": {
"id": "1456046457993048",
"name": "Richard Ettinson"
},
"to": {
"data": [
{
"id": "311620272349920",
"name": "Barbara Fallerman"
}
]
},
"with_tags": {
"data": [
{
"id": "311620272349920",
"name": "Barbara Fallerman"
}
]
},
"message": "I was gong out with her",
"actions": [
{
"name": "Comment",
"link": "https://www.facebook.com/311620272349920/posts/311718615673419"
},
{
"name": "Like",
"link": "https://www.facebook.com/311620272349920/posts/311718615673419"
}
]
}
例如,我设法通过
val extracted = (json \ "data" \"from").extract[PostFrom]
但是我担心如果使用此技术,我将需要多次传递Json来提取所需的所有值,这可能会导致性能下降.
But I worry that if I use this technique I will need to pass over the Json multiple times to extract all the values I need which could lead to a bad performance.
我如何才能从非相似对象数组中将这些字段提取到case类中?
How exactly could I extract these fields into case classes from the array of non similar objects?
我尝试使用以下case classes
:
abstract class BaseResponse()
case class Data(list:List[Post])
case class Post(id: String, post: PostFrom) extends BaseResponse
case class PostFrom(id: String, name:String)
哪个总是导致一个空的列表,有没有办法找回Data
类,其中包含我感兴趣的某些类的列表? (例如,顶级id
,from
和with_tags
)
Which always lead to an empty List, is there a way to get back a Data
class which has a list of certain classes which I am interested in? (As example the top level id
, from
and with_tags
)
推荐答案
我发现一种可能性是使用更多的case类而不是继承:
A possibility I found was to use more case classes instead of inheritance:
case class Root[T](data:Option[T])
case class Post(id: String, from: From, message: String)
case class From(id: String, name:String)
基本上,必须有一个采用某种图形响应对象的根对象,此外它是可选的,这样,如果响应解析出现问题,它就不会抛出异常.
Basically there has to be a root object which takes some kind of graphs response object, additionally it is optional so that it won't throw an exception if there was a problem with the parsing of the response.
然后我通过以下方式使用它:
I then used it in the following way:
val body = r.entity.asString
val json = parse(r.entity.asString)
val root = json.extract[Root[Post]]
root.data match {
case Some(post) =>
val tagger = Tagger(post.from.id, post.from.name, post.id, post.message)
log.info(s"We received $tagger")
originalSender ! RetrievedTagger(tagger)
case None => originalSender ! NoTaggerFound
}
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