How can I extract JSON values using for-comprehensions - scala

Question

I want to extract JSON values usgin for-comprehensions
my code is this:
import net.liftweb.json._
val json = parse("""
{
"took": 212,
"timed_out": false,
"_shards": {
"total": 5,
"successful": 5,
"failed": 0
},
"hits": {
"total": 4,
"max_score": 0.625,
"hits": [
{
"_index": "siteindex",
"_type": "posts",
"_id": "1",
"_score": 0.625,
"_source": {
"title": "title 1",
"content": "content 1"
},
"highlight": {
"title": [
"<b>title</b> 1"
]
}
},
{
"_index": "siteindex",
"_type": "posts",
"_id": "4",
"_score": 0.19178301,
"_source": {
"title": "title 4",
"content": "content 4"
},
"highlight": {
"title": [
"<b>title</b> 4"
]
}
},
{
"_index": "siteindex",
"_type": "posts",
"_id": "2",
"_score": 0.19178301,
"_source": {
"title": "title 2",
"content": "content 2"
},
"highlight": {
"title": [
"<b>title</b> 2"
]
}
},
{
"_index": "siteindex",
"_type": "posts",
"_id": "3",
"_score": 0.19178301,
"_source": {
"title": "title 3",
"content": "content 3"
},
"highlight": {
"title": [
"<b>title</b> 3"
]
}
}
]
}
}
""")
my "case class" is this:
case class Document(title:String, content:String)
my "for" is this:
val ret: List[Document] = for {
JObject(child) <- json
JField("title", JString(title)) <- child
JField("content", JString(content)) <- child
} yield (Document( title, content ))
and my "list" is this:
ret: List[Document] = List(Document(title 1,content 1), Document(title 4,content 4), Document(title 2,content 2), Document(title 3,content 3))
until here everything is fine!
but now i need something like this:
List(Document2(1,<b>title</b> 1,content 1), Document2(4,<b>title</b> 4,content 4), Document2(2,<b>title</b> 2,content 2), Document2(3,<b>title</b> 3,content 3))
i need the value of:
"highlight": {
"title": [
"<b>*</b> *"
]
}
and this:
"_id": "*",
in my list.
my "case class" is this:
case class Document2(_id:String, title:String, content:String)
i try this, but it does not work
val ret: List[Document2] = for {
JObject(child) <- json
JField("_id", JString(_id)) <- child
JField("title", JString(title)) <- child
JField("content", JString(content)) <- child
} yield (Document2( _id, title, content ))
i don't know, if there is a better way of data extraction for this json
but the result is this:
<console>:23: warning: `withFilter' method does not yet exist on net.liftweb.json.JValue, using `filter' method instead
JObject(child) <- json
ret: List[Document2] = List()
any suggestion please
thanks for your help

Answer 1

Here is an answer similar to the approach from #flav, but I'll give you the structure to map to the json and how to get your end result too. First, the case classes:
case class Document2(_id:String, title:String, content:String)
case class Results(hits:HitsList)
case class HitsList(hits:List[Hit])
case class Hit(_id:String, _source:Source, highlight:Highlight)
case class Source(title:String, content:String)
case class Highlight(title:List[String])
Then, the code for parsing it and converting it:
implicit val formats = DefaultFormats
val results = json.extract[Results]
val docs2 = results.hits.hits.map{ hit =>
Document2(hit._id, hit.highlight.title.head, hit._source.content)
}