用Spray-json解析一个简单的数组 [英] Parsing a simple array with Spray-json

问题描述

我正在尝试(但失败)弄清了Spray-json如何将json提要转换为对象.如果我有一个简单的键->值json提要，那么它似乎可以正常运行，但是我想要读取的数据在这样的列表中:

[{
    "name": "John",
    "age": "30"
},
{
    "name": "Tom",
    "age": "25"
}]

我的代码如下:

package jsontest

import spray.json._
import DefaultJsonProtocol._

object JsonFun {

  case class Person(name: String, age: String)
  case class FriendList(items: List[Person])

  object FriendsProtocol extends DefaultJsonProtocol {
    implicit val personFormat = jsonFormat2(Person)
    implicit val friendListFormat = jsonFormat1(FriendList)
  }

  def main(args: Array[String]): Unit = {

    import FriendsProtocol._

    val input = scala.io.Source.fromFile("test.json")("UTF-8").mkString.parseJson

    val friendList = input.convertTo[FriendList]

    println(friendList)
  }

}    

如果我更改测试文件，使其只有一个人不在数组中并运行val friendList = input.convertTo[Person]，则它可以工作并且所有内容都可以解析，但是一旦我尝试解析一个数组，它就会失败，并显示错误Object expected in field 'items'

有人能指出我做错了什么方向吗?

解决方案

好吧，就像花了很多时间试图使某些东西工作之后，立即将某些东西发布到StackOverflow之后的方式一样，我设法做到了这一点./p>

FriendsProtocol的正确实现是:

object FriendsProtocol extends DefaultJsonProtocol {
  implicit val personFormat = jsonFormat2(Person)
  implicit object friendListJsonFormat extends RootJsonFormat[FriendList] {
    def read(value: JsValue) = FriendList(value.convertTo[List[Person]])
    def write(f: FriendList) = ???
  } 
}

告诉Spray如何读取/写入(在我的情况下仅为读取)列表对象足以使其工作.

希望对别人有帮助！

I'm trying (and failing) to get my head around how spray-json converts json feeds into objects. If I have a simple key -> value json feed then it seems to work ok but the data I want to read comes in a list like this:

[{
    "name": "John",
    "age": "30"
},
{
    "name": "Tom",
    "age": "25"
}]

And my code looks like this:

package jsontest

import spray.json._
import DefaultJsonProtocol._

object JsonFun {

  case class Person(name: String, age: String)
  case class FriendList(items: List[Person])

  object FriendsProtocol extends DefaultJsonProtocol {
    implicit val personFormat = jsonFormat2(Person)
    implicit val friendListFormat = jsonFormat1(FriendList)
  }

  def main(args: Array[String]): Unit = {

    import FriendsProtocol._

    val input = scala.io.Source.fromFile("test.json")("UTF-8").mkString.parseJson

    val friendList = input.convertTo[FriendList]

    println(friendList)
  }

}    

If I change my test file so it just has a single person not in an array and run val friendList = input.convertTo[Person] then it works and everything parses but as soon as I try and parse an array it fails with the error Object expected in field 'items'

Can anyone point me the direction of what I'm doing wrong?

解决方案

Well, as is often the way immediately after posting something to StackOverflow after spending hours trying to get something working, I've managed to get this to work.

The correct implementation of FriendsProtocol was:

object FriendsProtocol extends DefaultJsonProtocol {
  implicit val personFormat = jsonFormat2(Person)
  implicit object friendListJsonFormat extends RootJsonFormat[FriendList] {
    def read(value: JsValue) = FriendList(value.convertTo[List[Person]])
    def write(f: FriendList) = ???
  } 
}

Telling Spray how to read / write (just read in my case) the list object is enough to get it working.

Hope that helps someone else!

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