         public static let cacheControl = "Cache-Control"
     }
     
+    // MARK: Content Type Constants
+    
+    public struct ContentType {
+        public static let formEncoded = "application/x-www-form-urlencoded"
+        public static let json = "application/json"
+    }
+    
     // MARK: Request Properties
     
     public let method: Method
     public let url: String
     public var parameters = [String : AnyObject]()
     public var headers = [String : String]()
-    public var parameterEncoding = ParameterEncoding.Percent
+    public var parameterEncoding = ParameterEncoding.Percent {
+        didSet {
+            if parameterEncoding == .JSON {
+                contentType = ContentType.json
+            }
+        }
+    }
     
     public var contentType: String? {
         set { headers[Headers.contentType] = newValue }

*/
public struct Request {
    
    // MARK: HTTP Methods

    public enum Method: String {
        case GET = "GET"

        }
    }
    
    // MARK: HTTP Header Constants
    
    public struct Headers {
        public static let userAgent = "User-Agent"
