How to serialize / deserialize GLib object(Will update later)

Background

How to compare two objects and generate the patch for them? It is a important step to forward Kangaroo 1.0. I don't know which library is the best way to solve this problem, So I start to study this problem.

Solution

In GLib framework, there are two libraries support to serialize / deserialize object, there are:

Library	Latest version	Website	Description
JSON-GLib	1.44	JSON-GLib (opens new window)	JSON-GLib implements a full JSON parser and generator using GLib and GObject, and integrates JSON with GLib data types.
GXML	0.16	GXML (opens new window)	GXml provides a GObject API for manipulating XML and a Serializable framework from GObject to XML.

Which library is suitable for this problem?

let us list a checklist to check which library is better for our problem:

Key item	GXML	JSON-GLib	Remark
Basic types	[x] Supported	[x] Supported	char/int/double/...
Boxed types	[ ] Unsupported	[x] Supported	Value/Variant/...
Object	[x] Supported	[x] Supported	GObject based object
Vala Array	[x] Supported	[ ] Unsupported	container type
Gee.ArrayList	[x] Supported	[ ] Unsupported	container type
Gee.HashMap	[x] Supported	[ ] Unsupported	container type
Gee.TreeMap	[x] Supported	[ ] Unsupported	container type
Gee.LinkedList	[ ] Unsupported	[ ] Unsupported	container type
GLib.Array	[ ] Unsupported	[ ] Unsupported	container type
GLib.List	[ ] Unsupported	[ ] Unsupported	container type
GLib.SList	[ ] Unsupported	[ ] Unsupported	container type
GLib.Queue	[ ] Unsupported	[ ] Unsupported	container type
GLib.HastTable	[ ] Unsupported	[ ] Unsupported	container type

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Advantage / Disadvantage of GXML

Advantage

1. Vala friendly
2. Support four kinds of Gee container.

Disadvantage

1. Missing GLib built-in container support.
2. Missing boxed type support

Advantage / Disadvantage of JSON-GLib

Advantage

1. support to register new type function to serialize / deserialize unsupported types, both boxed types and complex objects.
2. Boxed type and container friendly.

Disadvantage

1. Missing GLib built-in container support.

JSON-GLib is the choice

For Kangaroo project, the final choice is JSON-GLib, because it is boxed type and container friendly, and support to register new type function to serialize/deserialize unsupported types, so the user could handle all new GObject based type.

Example

GLib container serialization

    public class DbObject : GLib.Object, Json.Serializable
    {
        public Json.Object? meta { get; construct set; default = null; }
        public VersionSync version { get; set; default = VersionSync.UNKNOWN; }
        public virtual Value get_property (ParamSpec pspec)
        {
            Value prop_value = GLib.Value(pspec.value_type);
            (this as GLib.Object).get_property(pspec.name, ref prop_value);
            stdout.printf ("%s --> %s\n", prop_value.type_name(), prop_value.strdup_contents());
            return prop_value;
        }
        public virtual void set_property (ParamSpec pspec, Value value)
        {
            (this as GLib.Object).set_property (pspec.name, value);
        }
        public unowned ParamSpec? find_property (string name)
        {
            return ((ObjectClass) get_type ().class_ref ()).find_property (name);
        }
        public virtual Json.Node serialize_property (string property_name, Value @value, ParamSpec pspec)
        {
            if (@value.type ().is_a (typeof (Json.Object)))
            {
                var obj = @value as Json.Object;
                if (obj != null)
                {
                    var node = new Json.Node (NodeType.OBJECT);
                    node.set_object (obj);
                    return node;
                }
            }
            else if (@value.type ().is_a (typeof (Gee.ArrayList)))
            {
                unowned Gee.ArrayList<GLib.Object> list_value = @value as Gee.ArrayList<GLib.Object>;
                if (list_value != null || property_name == "data")
                {
                    var array = new Json.Array.sized (list_value.size);
                    foreach (var item in list_value)
                    {
                        array.add_element (gobject_serialize (item));
                    }
                    var node = new Json.Node (NodeType.ARRAY);
                    node.set_array (array);
                    return node;
                }
            }
            else if (@value.type ().is_a (typeof (GLib.Array)))
            {
                unowned GLib.Array<GLib.Object> array_value = @value as GLib.Array<GLib.Object>;
                if (array_value != null || property_name == "data")
                {
                    var array = new Json.Array.sized (array_value.length);
                    for (int i = 0; i < array_value.length; i++) {
                        array.add_element (gobject_serialize (array_value.index(i)));
                    }
                    var node = new Json.Node (NodeType.ARRAY);
                    node.set_array (array);
                    return node;
                }
            }            
            else if (@value.type ().is_a (typeof (HashTable)))
            {
                var obj = new Json.Object ();
                var ht_string = @value as HashTable<string, string>;
                if (ht_string != null)
                {
                    ht_string.foreach ((k, v) => {
                        obj.set_string_member (k, v);
                    });
                    var node = new Json.Node (NodeType.OBJECT);
                    node.set_object (obj);
                    return node;
                } else {
                    var ht_object = @value as HashTable<string, GLib.Object>;
                    if (ht_object != null)
                    {
                        ht_object.foreach ((k, v) => {
                            obj.set_member (k, gobject_serialize (v));
                        });    
                        var node = new Json.Node (NodeType.OBJECT);
                        node.set_object (obj);
                        return node;
                    }
                }
            }
            return default_serialize_property (property_name, @value, pspec);
        }
        public virtual bool deserialize_property (string property_name, out Value @value, ParamSpec pspec, Json.Node property_node)
        {
            return default_deserialize_property (property_name, out @value, pspec, property_node);
        }
    }

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Reference

GXml: Objects and Collections to XML and back (opens new window)

GXml 0.14 and Serialization (opens new window)

HowTo: GObject Serialization to XML using GXml (opens new window)

Serializing object property with Json.gobject_serialize? (opens new window)

json-api-object.vala (opens new window)

Is there no way to auto serialize any array with data to JSON? (opens new window)