使用 Scalatra 序列化 Java 和 Scala 对象

Serialisation of Java and Scala objects with Scalatra

我继承了一个提供 REST API 的遗留 Scalatra 应用程序。如果 returned 对象是一个 case class 构建在其他 case classes 上,那么 returned 对象的序列化工作完美。但是如果 return 从 Java 或 Scala class 创建的对象,它不会被 Scalatra 序列化。我只会得到 Object.toString() 的结果。那么我需要做什么才能正确序列化非大小写 classes?

这是我的class

class Snafu(sna: String, foo: String) {
}

这是我的 servlet:

class HealthServlet(implicit inj: Injector)
 extends ScalatraServlet with SLF4JLogging
 with JacksonJsonSupport
 with Injectable with InternalViaLocalhostOnlySupport {
 protected implicit val jsonFormats: Formats = DefaultFormats

 val healthStateCheck = inject[HealthStateCheck]

  before("/") {
  }

  get("/") {
    Ok(new Snafu("4", "2"))
  }
}

json4s 默认不支持非大小写 class 序列化。您需要为 classes 添加一个 CustomSerializer

class IntervalSerializer extends CustomSerializer[Interval](format => (
  {
    // Deserialize
    case JObject(JField("start", JInt(s)) :: JField("end", JInt(e)) :: Nil) =>
      new Interval(s.longValue, e.longValue)
  },
  {
    // Serialize
    case x: Interval =>
      JObject(JField("start", JInt(BigInt(x.startTime))) ::
        JField("end",   JInt(BigInt(x.endTime))) :: Nil)
  }
  ))

您还需要将这些序列化器添加到正在使用的json格式中。

  protected implicit lazy val jsonFormats: Formats = DefaultFormats + FieldSerializer[Interval]()

这是 json4s 文档中的示例,该示例已修改为显示一个工作 servlet 从常规 class.

返回序列化 json
import org.json4s._
import org.json4s.JsonAST.{JInt, JField, JObject}
import org.scalatra.json.JacksonJsonSupport

class Interval(start: Long, end: Long) {
  val startTime = start
  val endTime = end
}

class IntervalSerializer extends CustomSerializer[Interval](format => (
  {
    // Deserialize
    case JObject(JField("start", JInt(s)) :: JField("end", JInt(e)) :: Nil) =>
      new Interval(s.longValue, e.longValue)
  },
  {
    // Serialize
    case x: Interval =>
      JObject(JField("start", JInt(BigInt(x.startTime))) ::
        JField("end",   JInt(BigInt(x.endTime))) :: Nil)
  }
  ))

class IntervalServlet extends ScalatraServlet with ScalateSupport with JacksonJsonSupport {

  get("/intervalsample") {
    contentType = "application/json"

    val interval = new Interval(1, 2)

    Extraction.decompose(interval)
  }

  protected implicit lazy val jsonFormats: Formats = DefaultFormats + FieldSerializer[Interval]()

}