Play Framework 2.1.1 Json编写嵌套对象

Question

I've been trying to get my head around this all afternoon to no avail, Play 2.1.1 overhauled how the Json reads and writes work.

Basically I have a wrapper object that looks like:

case class CombinedUser(user: SocialUser, userdetails: UserDetails)

as you can see it contains 2 classes that I want to serialize and deserialize to json.

But I don't understand how I can get and set the fields in the subclasses using the new design.

For example

implicit val combinedUser2Reads = (
  (__ \ "email").read[String] and
  (__ \ "providerid").read[String] and
  (__ \ "firstname").read[String] and
  (__ \ "lastname").read[String] and
  (__ \ "fullname").read[String] and
  (__ \ "avatarurl").read[String] and
  (__ \ "address1").read[String] and
  (__ \ "address2").read[String] and
  (__ \ "address3").read[String] and
  (__ \ "city").read[String] and
  (__ \ "country").read[String] and
  (__ \ "phone").read[String] and
  (__ \ "publickey").as[String]
)(CombinedUser2.apply _)

I want a json blob that has most of the subclasses fields, all strings.

Because it uses the apply stuff, I don't see how I can create the subclasses before the mapping.

Any help or guidance is much appreciated.

Thanks

Tom

Answer 1

You can do it this way:

case class SocialUser(firstName: String, lastName: String)
case class UserDetails(avatarUrl: String, phone: String)
case class CombinedUser(user: SocialUser, userDetails: UserDetails)  
implicit val combinedUserReads: Reads[CombinedUser] = (
  (__ \ "user").read((
    (__ \ "firstName").read[String] and
    (__ \ "lastName").read[String]
  )(SocialUser)) and
  (__ \ "userDetails").read((
    (__ \ "avatarUrl").read[String] and
    (__ \ "phone").read[String]
  )(UserDetails))
)(CombinedUser)

However its better to create separated Reads :

implicit val socialUserReads = (
  (__ \ "firstName").read[String] and
  (__ \ "lastName").read[String]
)(SocialUser)    
implicit val userDetailsReads = (
  (__ \ "avatarUrl").read[String] and
  (__ \ "phone").read[String]
)(UserDetails)
implicit val combinedUserReads: Reads[CombinedUser] = (
  (__ \ "user").read[SocialUser] and
  (__ \ "userDetails").read[UserDetails]
)(CombinedUser)

Edit: for simple case classes, its possible to do :

implicit val socialUserReads = Json.format[SocialUser]
implicit val userDetailsReads = Json.format[UserDetails]
implicit val combinedUserReads = Json.format[CombinedUser]

Here is quite comprehensive introduction to JSON Reads and more.

How about partial objects? If I don't want to fill in every field in the constructor, can I pass empties or do I overload the constructor or similar?

Use Option :

case class CombinedUser(user: SocialUser, userDetails: Option[UserDetails])
//reads
implicit val combinedUserReads: Reads[CombinedUser] = (
  (__ \ "user").read[SocialUser] and
  (__ \ "userDetails").readOpt[UserDetails]
)(CombinedUser)
//writes
implicit val combinedUserWrites: Writes[CombinedUser] = (
  //socialUserWrites and userDetailsWrites must be in scope
  (__ \ "user").write[SocialUser] and
  (__ \ "userDetails").write[Option[UserDetails]]
)(unlift(CombinedUser.unapply))

val json = Json.obj(
  "user" -> Json.obj(
    "firstName" -> "Homer",
    "lastName" -> "Simpson"
  )
)
Json.fromJson[CombinedUser](json)
//JsSuccess(CombinedUser(SocialUser(Homer,Simpson),None),)