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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
import java.lang.reflect.Modifier
import scala.util.control.NonFatal
/**
* Provides the helpers for constructing custom JsonFormat implementations for types implementing the Product trait
* (especially case classes)
*/
trait ProductFormats extends ProductFormatsInstances {
this: StandardFormats =>
// 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 =>
var fieldFound = false
try {
val fieldValue = x.fields(fieldName)
fieldFound = true
reader.read(fieldValue)
}
catch {
case e: NoSuchElementException if !fieldFound =>
if (reader.isInstanceOf[OptionFormat[_]]) None.asInstanceOf[T]
else deserializationError("Object is missing required member '" + fieldName + "'", e)
}
case _ => deserializationError("Object expected in field '" + fieldName + "'")
}
}
protected def extractFieldNames(classManifest: ClassManifest[_]): Array[String] = {
val clazz = classManifest.erasure
try {
// copy methods have the form copy$default$N(), we need to sort them in order, but must account for the fact
// that lexical sorting of ...8(), ...9(), ...10() is not correct, so we extract N and sort by N.toInt
val copyDefaultMethods = clazz.getMethods.filter(_.getName.startsWith("copy$default$")).sortBy(
_.getName.drop("copy$default$".length).takeWhile(_ != '(').toInt)
val fields = clazz.getDeclaredFields.filterNot { f =>
f.getName.startsWith("$") || Modifier.isTransient(f.getModifiers) || Modifier.isStatic(f.getModifiers)
}
if (copyDefaultMethods.length != fields.length)
sys.error("Case class " + clazz.getName + " declares additional fields")
if (fields.zip(copyDefaultMethods).exists { case (f, m) => f.getType != m.getReturnType })
sys.error("Cannot determine field order of case class " + clazz.getName)
fields.map(_.getName)
} catch {
case NonFatal(ex) => throw new RuntimeException("Cannot automatically determine case class field names and order " +
"for '" + clazz.getName + "', please use the 'jsonFormat' overload with explicit field name specification", ex)
}
}
}
/**
* 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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