3 files changed, 17 insertions, 1 deletions
diff --git a/src/main/scala/cc/spray/json/AdditionalFormats.scala b/src/main/scala/cc/spray/json/AdditionalFormats.scala
index e8b59c7..db9d3ba 100644
--- a/src/main/scala/cc/spray/json/AdditionalFormats.scala
+++ b/src/main/scala/cc/spray/json/AdditionalFormats.scala
@@ -27,17 +27,26 @@ trait AdditionalFormats {
     def read(value: JsValue) = value
   }
 
+  /**
+   * Constructs a JsonFormat from its two parts, JsonReader and JsonWriter.
+   */
   def jsonFormat[T](reader: JsonReader[T], writer: JsonWriter[T]) = new JsonFormat[T] {
     def write(obj: T) = writer.write(obj)
     def read(json: JsValue) = reader.read(json)
   }
 
+  /**
+   * Turns a JsonWriter into a JsonFormat that throws an UnsupportedOperationException for reads.
+   */
   def lift[T](writer :JsonWriter[T]) = new JsonFormat[T] {
     def write(obj: T): JsValue = writer.write(obj)
     def read(value: JsValue) =
       throw new UnsupportedOperationException("JsonReader implementation missing")
   }
 
+  /**
+   * Turns a JsonReader into a JsonFormat that throws an UnsupportedOperationException for writes.
+   */
   def lift[T <: AnyRef](reader :JsonReader[T]) = new JsonFormat[T] {
     def write(obj: T): JsValue =
       throw new UnsupportedOperationException("No JsonWriter[" + obj.getClass + "] available")
diff --git a/src/main/scala/cc/spray/json/JsValue.scala b/src/main/scala/cc/spray/json/JsValue.scala
index a02de0f..86dbb06 100644
--- a/src/main/scala/cc/spray/json/JsValue.scala
+++ b/src/main/scala/cc/spray/json/JsValue.scala
@@ -55,7 +55,7 @@ object JsValue {
     case x: collection.Seq[_] => JsArray(x.toList.map(JsValue.apply))
     case x => throw new IllegalArgumentException(x.toString + " cannot be converted to a JsValue")
   }
-  
+
   private def fromSeq(seq: Iterable[(_, _)]) = {
     val list = ListBuffer.empty[JsField]
     seq.foreach {
diff --git a/src/main/scala/cc/spray/json/ProductFormats.scala b/src/main/scala/cc/spray/json/ProductFormats.scala
index ec58d22..d0263c8 100644
--- a/src/main/scala/cc/spray/json/ProductFormats.scala
+++ b/src/main/scala/cc/spray/json/ProductFormats.scala
@@ -422,6 +422,13 @@ trait ProductFormats {
   }
 }
 
+/**
+ * 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 =>