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/*
* Copyright (C) 2011 Mathias Doenitz
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package spray.json
/**
* Provides the helpers for constructing custom JsonFormat implementations for types implementing the Product trait
* (especially case classes)
*/
trait ProductFormats extends ProductFormatsInstances {
this: StandardFormats =>
def jsonFormat0[T](construct: () => T): RootJsonFormat[T] =
new RootJsonFormat[T] {
def write(p: T) = JsObject()
def read(value: JsValue) = value match {
case JsObject(_) => construct()
case _ => throw new DeserializationException("Object expected")
}
}
// helpers
protected def productElement2Field[T](fieldName: String, p: Product, ix: Int, rest: List[JsField] = Nil)
(implicit writer: JsonWriter[T]): List[JsField] = {
val value = p.productElement(ix).asInstanceOf[T]
writer match {
case _: OptionFormat[_] if (value == None) => rest
case _ => (fieldName, writer.write(value)) :: rest
}
}
protected def fromField[T](value: JsValue, fieldName: String)
(implicit reader: JsonReader[T]) = value match {
case x: JsObject if
(reader.isInstanceOf[OptionFormat[_]] &
!x.fields.contains(fieldName)) =>
None.asInstanceOf[T]
case x: JsObject =>
try reader.read(x.fields(fieldName))
catch {
case e: NoSuchElementException =>
deserializationError("Object is missing required member '" + fieldName + "'", e, fieldName :: Nil)
case DeserializationException(msg, cause, fieldNames) =>
deserializationError(msg, cause, fieldName :: fieldNames)
}
case _ => deserializationError("Object expected in field '" + fieldName + "'", fieldNames = fieldName :: Nil)
}
}
/**
* This trait supplies an alternative rendering mode for optional case class members.
* Normally optional members that are undefined (`None`) are not rendered at all.
* By mixing in this trait into your custom JsonProtocol you can enforce the rendering of undefined members as `null`.
* (Note that this only affect JSON writing, spray-json will always read missing optional members as well as `null`
* optional members as `None`.)
*/
trait NullOptions extends ProductFormats {
this: StandardFormats =>
override protected def productElement2Field[T](fieldName: String, p: Product, ix: Int, rest: List[JsField])
(implicit writer: JsonWriter[T]) = {
val value = p.productElement(ix).asInstanceOf[T]
(fieldName, writer.write(value)) :: rest
}
}
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