Question

我的Runner代码看起来像

import java.io.File

import org.json4s._
import org.json4s.native.JsonMethods._

object WorkOrderParser {
  implicit val formats = DefaultFormats
  def get(workOrderJson: File): List[WorkOrderItem] = {
    parse(workOrderJson).extract[List[WorkOrderItem]]
  }

  def main(args: Array[String]) {
    println(WorkOrderParser.get(new File("src/main/resources/workConfigSample.json")))
  }
}

我的案例类看起来像

import java.io.File

sealed trait FilePostProcessingAction

case object delete extends FilePostProcessingAction

case object move extends FilePostProcessingAction

case class WorkOrderItem(configName: String,
                         logSource: File,
                         logType: String,
                         afterProcessingFileAction: FilePostProcessingAction,
                         recursiveFind: Option[Boolean] = Some(false),
                         processZipFiles: Option[Boolean] = Some(false))

我的示例JSON看起来像

[
  {
    "configName": "bluecoat",
    "logSource": "/root/fw1/logs/bc",
    "logType": "bluecoat",
    "recursiveFind": true,
    "processZipFiles": false,
    "afterProcessingFileAction": "delete"
  },
  {
    "configName": "mcAfee",
    "logSource": "/root/fw1/logs/mcafee",
    "logType": "mcafee",
    "recursiveFind": true,
    "processZipFiles": true,
    "afterProcessingFileAction": "delete"
  }
]

当我运行时，我得到了

Exception in thread "main" org.json4s.package$MappingException: No usable value for logSource
Parsed JSON values do not match with class constructor
args=
arg types=
constructor=org.json4s.reflect.Executable@1fa268de
    at org.json4s.reflect.package$.fail(package.scala:93)
    at org.json4s.Extraction$ClassInstanceBuilder.org$json4s$Extraction$ClassInstanceBuilder$$buildCtorArg(Extraction.scala:509)
    at org.json4s.Extraction$ClassInstanceBuilder$$anonfun$14.apply(Extraction.scala:529)
    at org.json4s.Extraction$ClassInstanceBuilder$$anonfun$14.apply(Extraction.scala:529)
    at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:245)
    at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:245)
    at scala.collection.mutable.ResizableArray$class.foreach(ResizableArray.scala:59)
    at scala.collection.mutable.ArrayBuffer.foreach(ArrayBuffer.scala:48)
    at scala.collection.TraversableLike$class.map(TraversableLike.scala:245)
    at scala.collection.AbstractTraversable.map(Traversable.scala:104)
    at org.json4s.Extraction$ClassInstanceBuilder.org$json4s$Extraction$ClassInstanceBuilder$$instantiate(Extraction.scala:517)
    at org.json4s.Extraction$ClassInstanceBuilder$$anonfun$result$6.apply(Extraction.scala:564)
    at org.json4s.Extraction$ClassInstanceBuilder$$anonfun$result$6.apply(Extraction.scala:559)
    at org.json4s.Extraction$.org$json4s$Extraction$$customOrElse(Extraction.scala:573)
    at org.json4s.Extraction$ClassInstanceBuilder.result(Extraction.scala:559)
    at org.json4s.Extraction$.extract(Extraction.scala:394)
    at org.json4s.Extraction$CollectionBuilder$$anonfun$6.apply(Extraction.scala:403)
    at org.json4s.Extraction$CollectionBuilder$$anonfun$6.apply(Extraction.scala:403)
    at scala.collection.immutable.List.map(List.scala:273)
    at org.json4s.Extraction$CollectionBuilder.mkCollection(Extraction.scala:403)
    at org.json4s.Extraction$CollectionBuilder.result(Extraction.scala:423)
    at org.json4s.Extraction$.extract(Extraction.scala:377)
    at org.json4s.Extraction$.extract(Extraction.scala:43)
    at org.json4s.ExtractableJsonAstNode.extract(ExtractableJsonAstNode.scala:21)
    at com.logprocessor.processor.workOrder.WorkOrderParser$.get(WorkOrderParser.scala:11)
    at com.logprocessor.processor.workOrder.WorkOrderParser$.main(WorkOrderParser.scala:15)
    at com.logprocessor.processor.workOrder.WorkOrderParser.main(WorkOrderParser.scala)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:497)
    at com.intellij.rt.execution.application.AppMain.main(AppMain.java:144)
Caused by: org.json4s.package$MappingException: Parsed JSON values do not match with class constructor
args=
arg types=
constructor=org.json4s.reflect.Executable@1fa268de
    at org.json4s.Extraction$ClassInstanceBuilder.org$json4s$Extraction$ClassInstanceBuilder$$instantiate(Extraction.scala:542)
    at org.json4s.Extraction$ClassInstanceBuilder$$anonfun$result$6.apply(Extraction.scala:564)
    at org.json4s.Extraction$ClassInstanceBuilder$$anonfun$result$6.apply(Extraction.scala:559)
    at org.json4s.Extraction$.org$json4s$Extraction$$customOrElse(Extraction.scala:573)
    at org.json4s.Extraction$ClassInstanceBuilder.result(Extraction.scala:559)
    at org.json4s.Extraction$.extract(Extraction.scala:394)
    at org.json4s.Extraction$ClassInstanceBuilder.org$json4s$Extraction$ClassInstanceBuilder$$buildCtorArg(Extraction.scala:497)
    ... 30 more

但是，当我将我的案例类中的类型更改为String（logSource和afterProcessingFileAction）时，它可以正常工作

我做错了什么？我正在使用https://github.com/json4s/json4s来实现此目标

Answer 1

也许几年为时已晚，但是我看到2k的视图，所以让我们回答一下：）

这是因为json4s正在寻找如何对List [WorkOrderItem]进行反序列化，并且找不到与extract [T]相匹配的构造函数，在您的情况下，它是extract [List [WorkOrderItem]]。

我相信您需要创建一个自定义解串器并将其注册为受支持的格式之一。注意：可能还有其他方法，例如使用提示或其他功能，但是我昨天才开始使用json4s，所以我有点菜鸟。

例如-

创建案例类-

case class DynamicStringList(values: List[String]) {
  def show() {
    values.foreach(println)
  }
}

创建您的序列化器。下面是一个工作示例-

case object DynamicStringListSerializer extends CustomSerializer[DynamicStringList] (format => ({
  case JString(stringValue) => DynamicStringList(List(stringValue))
  case JArray(stringValues) => {
    implicit val formats = DefaultFormats
    def jsonJValueToString(jsonString: JValue)(implicit formats: Formats) : String = {
      jsonString.extract[String]
    }
    val dynamicList = stringValues.map(jsonJValueToString).toList
    DynamicStringList(dynamicList) //DynamicStringArray.toArray(stringValues)
  }
}, {
  // TODO - This is the serialize function to JArray, however we will probably never use it so not done for now
  case dynamicList: DynamicStringList => JNothing
}
))

在所需的对象/类中将其注册为受支持的格式-

import org.json4s.DefaultFormats
import com.myserializers.DynamicStringListSerializer

object MyJSONUtils {   
    implicit val formats = DefaultFormats + DynamicStringListSerializer

做些事情（假设您拥有所需的所有其他json导入）

parse(json_message_as_string).extract[DynamicStringList]

解析的JSON值与类构造函数不匹配

1 个答案: