Add JsonFormat for JsValues, some more helpers

1 files changed, 62 insertions, 0 deletions

diff --git a/src/main/scala/cc/spray/json/AdditionalFormats.scala b/src/main/scala/cc/spray/json/AdditionalFormats.scala
new file mode 100644
index 0000000..62a30e7
--- /dev/null
+++ b/src/main/scala/cc/spray/json/AdditionalFormats.scala
@@ -0,0 +1,62 @@
+/*
+ * Original implementation (C) 2009-2011 Debasish Ghosh
+ * Adapted and extended in 2011 by 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 cc.spray.json
+
+/**
+  * Provides additional JsonFormats and helpers
+ */
+trait AdditionalFormats {
+
+  implicit object JsValueFormat extends JsonFormat[JsValue] {
+    def write(value: JsValue) = value
+    def read(value: JsValue) = value
+  }
+
+  def formatFromWriter[T :JsonWriter] = new JsonFormat[T] {
+    def write(obj: T) = obj.toJson
+    def read(value: JsValue) = throw new RuntimeException("JsonFormat constructed from JsonWriter can't read from JSON")
+  }
+
+  def formatFromReader[T :JsonReader] = new JsonFormat[T] {
+    def write(obj: T) = throw new RuntimeException("JsonFormat constructed from JsonReader can't write JSON")
+    def read(value: JsValue) = value.fromJson[T]
+  }
+
+  /**
+   * Lazy wrapper around serialization. Useful when you want to serialize (mutually) recursive structures.
+   */
+  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);
+  }
+
+  /**
+   * Wraps an existing JsonReader with Exception protection.
+   */
+  def safeReader[A :JsonReader] = new JsonReader[Either[Exception, A]] {
+    def read(json: JsValue) = {
+      try {
+        Right(json.fromJson)
+      } catch {
+        case e: Exception => Left(e)
+      }
+    }
+  }
+
+}
\ No newline at end of file