scala Spray-Json：如何解析 Json 数组？
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Spray-Json: How to parse a Json Array?
提问by abronan
I'm new to the Spray-Json API and I'm trying to parse a Json response from the Docker REST API.
我是 Spray-Json API 的新手，我正在尝试解析来自 Docker REST API 的 Json 响应。
Thereis a clean example of the usage of Spray-Json to parse this Google Map Json response :
有一个使用 Spray-Json 来解析此 Google Map Json 响应的清晰示例：
{
"results" : [
{
"elevation" : 8815.7158203125,
"location" : {
"lat" : 27.988056,
"lng" : 86.92527800000001
},
"resolution" : 152.7032318115234
}
],
"status" : "OK"
}
In the above example the outermost level is an Object. However, I need to directly parse a Json response whose outermost level is an Arraycomposed of containers information as shown below :
在上面的例子中，最外层是一个Object. 但是，我需要直接解析一个 Json 响应，其最外层是Array由容器信息组成的，如下所示：
[
{
"Id": "8dfafdbc3a40",
"Image": "base:latest",
"Command": "echo 1",
"Created": 1367854155,
"Status": "Exit 0",
"Ports":[{"PrivatePort": 2222, "PublicPort": 3333, "Type": "tcp"}],
"SizeRw":12288,
"SizeRootFs":0
},
{ ... },
{ ... }
]
Here is a code that I adapted from the Google map example :
这是我改编自 Google 地图示例的代码：
package main
import ...
case class Container(id: String, image: String, command: String, created: Long, status: String, ports: List[Port], sizeRW: Long, sizeRootFs: Long)
case class Port(privatePort: Long, publicPort: Long, portType: String)
case class DockerApiResult[T](results: List[T])
object ContainerListJsonProtocol extends DefaultJsonProtocol {
implicit val portFormat = jsonFormat3(Port)
implicit val containerFormat = jsonFormat8(Container)
implicit def dockerApiResultFormat[T :JsonFormat] = jsonFormat1(DockerApiResult.apply[T])
}
object Main extends App {
implicit val system = ActorSystem("simple-spray-client")
import system.dispatcher // execution context for futures below
val log = Logging(system, getClass)
log.info("Requesting containers info...")
import ContainerListJsonProtocol._
import SprayJsonSupport._
val pipeline = sendReceive ~> unmarshal[DockerApiResult[Container]]
val responseFuture = pipeline {
Get("http://<ip-address>:4243/containers/json")
}
responseFuture onComplete {
case Success(DockerApiResult(Container(_,_,_,_,_,_,_,_) :: _)) =>
log.info("Id of the found image: {} ")
shutdown()
case Success(somethingUnexpected) =>
log.warning("The Docker API call was successful but returned something unexpected: '{}'.", somethingUnexpected)
shutdown()
case Failure(error) =>
log.error(error, "Couldn't get containers information")
shutdown()
}
def shutdown(): Unit = {
IO(Http).ask(Http.CloseAll)(1.second).await
system.shutdown()
}
}
And below is the exception I get (Object expected) :
下面是我得到的例外 ( Object expected)：
spray.httpx.PipelineException: MalformedContent(Object expected,Some(spray.json.DeserializationException: Object expected))
I certainly miss something obvious but How to parse a Json Array using Spray-Json?
我当然想念一些明显的东西，但是如何使用 Spray-Json 解析 Json 数组？
Also, is there a simple way to do this without having to deal with custom JsonFormat or RootJsonFormat?
另外，是否有一种简单的方法可以做到这一点而不必处理自定义 JsonFormat 或 RootJsonFormat？
回答by kong
By doing unmarshal[DockerApiResult[Container]], you're telling spray-json that you expect the format to be a json object of the form:
通过这样做unmarshal[DockerApiResult[Container]]，您告诉 Spray-json 您希望格式是以下形式的 json 对象：
{ results: [...] }
since case class DockerApiResult[T](results: List[T])is defined as an object with a single results field containing a list.
因为case class DockerApiResult[T](results: List[T])被定义为具有包含列表的单个结果字段的对象。
Instead you need to do:
相反，您需要执行以下操作：
unmarshal[List[Container]]
and then operate on the resulting list directly (or wrap it in a DockerApiResult after it has been parsed by spray-json).
然后直接对结果列表进行操作（或者在被spray-json解析后包装在一个DockerApiResult中）。
If you want spray-json to unmarshal directly into a DockerApiResult, you can write a JsonFormat with something like:
如果您希望 Spray-json 直接解组到 DockerApiResult 中，您可以编写一个 JsonFormat ，如下所示：
implicit object DockerApiResultFormat extends RootJsonFormat[DockerApiResult] {
def read(value: JsValue) = DockerApiResult(value.convertTo[List[Container]])
def write(obj: DockerApiResult) = obj.results.toJson
}
回答by Marco Aurelio
fought with this a little and found a way to convert to JsArray from a json parsed string using spray:
对此进行了一些斗争，并找到了一种使用喷雾从 json 解析字符串转换为 JsArray 的方法：
import spray.json._ //parseJson
val kkkk =
"""
|[{"a": "1"}, {"b": "2"}]
""".stripMargin.parseJson.asInstanceOf[JsArray]
