Http Server: Allow extending the json interface with a common base class

To allow extending the json interface for user defined types a common
jsonable class was added.

This class has a single method to_json.
To add a user define class, inherit the jsonable class and implement the
to_json method.

The formatter was changed to use that.

Signed-off-by: Amnon Heiman <[email protected]>
Signed-off-by: Pekka Enberg <[email protected]>

modules/httpserver/json/formatter.cc

@@ -63,7 +63,7 @@ string formatter::to_json(const date_time& d)
     return res + "\"";
 }
 
-string formatter::to_json(const json_base& obj) {
+string formatter::to_json(const jsonable& obj) {
     return obj.to_json();
 }
 

modules/httpserver/json/formatter.hh

@@ -16,7 +16,7 @@ namespace httpserver {
 
 namespace json {
 
-struct json_base;
+struct jsonable;
 
 typedef struct tm date_time;
 
@@ -105,7 +105,7 @@ public:
      * @param obj the date_time to format
      * @return the given json object in a json format
      */
-    static std::string to_json(const json_base& obj);
+    static std::string to_json(const jsonable& obj);
 
     /**
      * return a json formated unsigned long

modules/httpserver/json/json_elements.hh

@@ -135,6 +135,16 @@ public:
     std::vector<T> elements;
 };
 
+class jsonable {
+public:
+    virtual ~jsonable() = default;
+    /**
+     * create a foramted string of the object.
+     * @return the object formated.
+     */
+    virtual std::string to_json() const = 0;
+};
+
 /**
  * The base class for all json objects
  * It holds a list of all the element in it,
@@ -145,7 +155,7 @@ public:
  * are known in advance and in practice mimic
  * reflection
  */
-struct json_base {
+struct json_base : public jsonable {
 
     virtual ~json_base() = default;