Add RootJsonReader and RootJsonWriter as well as some helper methods, closes #10

2 files changed, 40 insertions, 2 deletions

diff --git a/src/main/scala/cc/spray/json/AdditionalFormats.scala b/src/main/scala/cc/spray/json/AdditionalFormats.scala
index dc78115..889fdaf 100644
--- a/src/main/scala/cc/spray/json/AdditionalFormats.scala
+++ b/src/main/scala/cc/spray/json/AdditionalFormats.scala
@@ -36,6 +36,12 @@ trait AdditionalFormats {
   }
 
   /**
+   * Constructs a RootJsonFormat from its two parts, RootJsonReader and RootJsonWriter.
+   */
+  def rootJsonFormat[T](reader: RootJsonReader[T], writer: RootJsonWriter[T]) =
+    rootFormat(jsonFormat(reader, writer))
+
+  /**
    * Turns a JsonWriter into a JsonFormat that throws an UnsupportedOperationException for reads.
    */
   def lift[T](writer :JsonWriter[T]) = new JsonFormat[T] {
@@ -45,6 +51,12 @@ trait AdditionalFormats {
   }
 
   /**
+   * Turns a RootJsonWriter into a RootJsonFormat that throws an UnsupportedOperationException for reads.
+   */
+  def lift[T](writer :RootJsonWriter[T]): RootJsonFormat[T] =
+    rootFormat(lift(writer :JsonWriter[T]))
+
+  /**
    * Turns a JsonReader into a JsonFormat that throws an UnsupportedOperationException for writes.
    */
   def lift[T <: AnyRef](reader :JsonReader[T]) = new JsonFormat[T] {
@@ -54,15 +66,29 @@ trait AdditionalFormats {
   }
 
   /**
+   * Turns a RootJsonReader into a RootJsonFormat that throws an UnsupportedOperationException for writes.
+   */
+  def lift[T <: AnyRef](reader :RootJsonReader[T]): RootJsonFormat[T] =
+    rootFormat(lift(reader :JsonReader[T]))
+
+  /**
    * Lazy wrapper around serialization. Useful when you want to serialize (mutually) recursive structures.
    */
-  def lazyFormat[T](format: => JsonFormat[T]) = new JsonFormat[T]{
+  def lazyFormat[T](format: => JsonFormat[T]) = new JsonFormat[T] {
     lazy val delegate = format;
     def write(x: T) = delegate.write(x);
     def read(value: JsValue) = delegate.read(value);
   }
 
   /**
+   * Explicitly turns a JsonFormat into a RootJsonFormat.
+   */
+  def rootFormat[T](format: JsonFormat[T]) = new RootJsonFormat[T] {
+    def write(obj: T) = format.write(obj)
+    def read(json: JsValue) = format.read(json)
+  }
+
+  /**
    * Wraps an existing JsonReader with Exception protection.
    */
   def safeReader[A :JsonReader] = new JsonReader[Either[Exception, A]] {
diff --git a/src/main/scala/cc/spray/json/JsonFormat.scala b/src/main/scala/cc/spray/json/JsonFormat.scala
index 01b9f80..683a823 100644
--- a/src/main/scala/cc/spray/json/JsonFormat.scala
+++ b/src/main/scala/cc/spray/json/JsonFormat.scala
@@ -53,7 +53,19 @@ object JsonWriter {
 trait JsonFormat[T] extends JsonReader[T] with JsonWriter[T]
 
 /**
+ * A special JsonReader capable of reading a legal JSON root object, i.e. either a JSON array or a JSON object.
+ */
+@implicitNotFound(msg = "Cannot find RootJsonReader or RootJsonFormat type class for ${T}")
+trait RootJsonReader[T] extends JsonReader[T]
+
+/**
+ * A special JsonWriter capable of writing a legal JSON root object, i.e. either a JSON array or a JSON object.
+ */
+@implicitNotFound(msg = "Cannot find RootJsonWriter or RootJsonFormat type class for ${T}")
+trait RootJsonWriter[T] extends JsonWriter[T]
+
+/**
  * A special JsonFormat signaling that the format produces a legal JSON root object, i.e. either a JSON array
  * or a JSON object.
  */
-trait RootJsonFormat[T] extends JsonFormat[T]
\ No newline at end of file
+trait RootJsonFormat[T] extends JsonFormat[T] with RootJsonReader[T] with RootJsonWriter[T]
\ No newline at end of file