如何使用 JSON Spray for HashMap 字段支持 Akka HTTP 中的编组和解组？

Question

我有以下情况类：

import scala.collection.immutable.HashMap
final case class GuiApplication(testSuites: TestSuites)
final case class GuiApplications(var applications: HashMap[Id, GuiApplication])
final case class Id(val id: Long)
final case class TestSuite()
final case class TestSuites(var testSuites: HashMap[Id, TestSuite])

编组定义：

implicit val applicationsMapFormat = jsonFormat0(HashMap[Id, GuiApplication])
implicit val testsuitesMapFormat = jsonFormat0(HashMap[Id, TestSuite])
implicit val idFormat = jsonFormat1(Id)
implicit val testSuiteFormat = jsonFormat0(TestSuite)
implicit val testSuitesFormat = jsonFormat1(TestSuites)
implicit val applicationFormat = jsonFormat1(GuiApplication)
implicit val applicationsFormat = jsonFormat1(GuiApplications)

但我仍然遇到这些编译错误：

type mismatch;
[error]  found   : Seq[(Id, GuiApplication)] => scala.collection.immutable.HashMap[Id,GuiApplication]
[error]  required: () => ?
[error]  Note: implicit value applicationsMapFormat is not applicable here because it comes after the application point and it lacks an explicit result type
[error]   implicit val applicationsMapFormat = jsonFormat0(HashMap[Id, GuiApplication])
[error]                                                           ^

如果删除前两个隐含函数，则会出现其他编译错误。如何在 Scala 中为地图类型定义隐式 JSON 格式？

Answer 1

您只需编写您的自定义 RootJsonFormat[scala.collection.immutable.HashMap[Id,GuiApplication]] 并将其添加到您的路由范围内：

implicit val hashMapFormat: RootJsonFormat[scala.collection.immutable.HashMap[Id,GuiApplication]] = new RootJsonFormat[scala.collection.immutable.HashMap[Id,GuiApplication]] {
  override def write(obj: scala.collection.immutable.HashMap[Long, String]): JsValue = ???
  override def read(json: JsValue): scala.collection.immutable.HashMap[Id,GuiApplication]  = ???
}

如何使用 JSON Spray for HashMap 字段支持 Akka HTTP 中的编组和解组？

How to support marshalling and unmarshalling in Akka HTTP with JSON Spray for HashMap fields?

scala

spray-json

akka-http