scala - akka http 使用 Json 支持和 xmlsupport

Question

当部门为“hr”时，我想以 xml 格式打印数据，而当部门为“tech”时，我想以 json 格式打印数据。

我们可以使用Spray-json 支持 https://doc.akka.io/docs/akka-http/current/common/json-support.html和 XML 支持 https://doc.akka.io/docs/akka-http/current/common/xml-support.html一起

 private[rest] def route =
  (pathPrefix("employee") & get) {
    path(Segment) { id =>
      parameters('department ? "") { (flag) =>
        extractUri { uri =>
          complete {
            flag match {
              case "hr": =>  {

            HttpEntity(MediaTypes.`application/xml`.withCharset(HttpCharsets.`UTF-8`),"hr department")
            }
              case "tech" =>{
                HttpEntity(ContentType(MediaTypes.`application/json`), mapper.writeValueAsString("tech department"))

              }

            }
          }
        }
      }
    }
  }

我尝试过的解决方案我通过使用 JsonProtocols 和 ScalaXmlSupport 尝试了以下操作，我得到了预期为 ToResponseMarshallable 的编译错误，但发现了 Department

case class department(name:String)
private[rest] def route =
  (pathPrefix("employee") & get) {
    path(Segment) { id =>
      parameters('department ? "") { (flag) =>
        extractUri { uri =>
          complete {
            flag match {
              case "hr": =>  {

            complete(department(name =flag))
            }
              case "tech" =>{
                complete(department(name =flag))

              }

            }
          }
        }
      }
    }
  }

Answer 1

我认为您必须克服几个问题才能实现您想要的目标:

1. 您想要根据请求参数自定义响应类型。这意味着基于标准隐式的编码(marshal)处理对您不起作用，您必须执行一些显式步骤

2. 您想要将一些业务对象编码到 XML 字符串中。不幸的是，ScalaXmlSupport您引用的不支持此功能，它只能将 XML 树编码到响应中。因此您需要一些可以执行 XML 序列化的库。一种选择是使用 jackson-dataformat-xml与 jackson-module-scala 。这也意味着您必须编写自己的自定义 Marshaller。幸运的是，这并不难。

这里有一些可能适合您的简单代码:

import akka.http.scaladsl.marshalling.{ToResponseMarshallable, Marshaller}

// json marshalling
import akka.http.scaladsl.marshallers.sprayjson.SprayJsonSupport
import spray.json._
import spray.json.DefaultJsonProtocol._
implicit val departmentFormat = DefaultJsonProtocol.jsonFormat1(department)
val departmentJsonMarshaller = SprayJsonSupport.sprayJsonMarshaller[department]

// xml marshalling, need to write a custom Marshaller
// there are several MediaTypes for XML such as `application/xml` and `text/xml`, you'll have to choose the one you need.
val departmentXmlMarshaller = Marshaller.StringMarshaller.wrap(MediaTypes.`application/xml`)((d: department) => {
  import com.fasterxml.jackson.dataformat.xml.XmlMapper
  import com.fasterxml.jackson.module.scala.DefaultScalaModule
  val mapper = new XmlMapper()
  mapper.registerModule(DefaultScalaModule)
  mapper.writeValueAsString(d)
})


private val route =
  (pathPrefix("employee") & get) {
    path(Segment) { id =>
      parameters('department ? "") { (flag) =>
        extractUri { uri => {
          flag match {
            case "hr" => {
              // explicitly use the XML marshaller 
              complete(ToResponseMarshallable(department(name = flag))(departmentXmlMarshaller))
            }
            case "tech" => {
              // explicitly use the JSON marshaller 
              complete(ToResponseMarshallable(department(name = flag))(departmentJsonMarshaller))
            }
          }
        }
        }
      }
    }
  }

请注意，为了让 Jackson XML 序列化器正常工作，department 类应该是顶级类，否则您将收到有关错误根名称的神秘错误。