Flavio Castelli

Just a quick note: I have just moved QJson source code to this git repository hosted by gitorious.

I’ll keep the code on KDE’s svn synchronized with the git repository.

Some days ago I introduced the possibility to serialize a QObject instance to JSON. Today I’m going to show you the opposite operation: initializing a QObject using a JSON object.

I refactored a bit my latest changes: I created a new class called QObjectHelper that provides the methods required to convert a QObject instance to a QVariantMap and vice-versa.

This class can be used in conjunction with the Serializer and Parser classes to serialize and deserialize QObject instances to and from JSON.

Let me show a quick example, suppose the declaration of Person class looks like this:

class Person : public QObject
{
  Q_OBJECT

  Q_PROPERTY(QString name READ name WRITE setName)
  Q_PROPERTY(int phoneNumber READ phoneNumber WRITE setPhoneNumber)
  Q_PROPERTY(Gender gender READ gender WRITE setGender)
  Q_PROPERTY(QDate dob READ dob WRITE setDob)
  Q_ENUMS(Gender)

public:
    Person(QObject* parent = 0);
    ~Person();

    QString name() const;
    void setName(const QString& name);

    int phoneNumber() const;
    void setPhoneNumber(const int  phoneNumber);

    enum Gender {Male, Female};
    void setGender(Gender gender);
    Gender gender() const;

    QDate dob() const;
    void setDob(const QDate& dob);

  private:
    QString m_name;
    int m_phoneNumber;
    Gender m_gender;
    QDate m_dob;
};

From QObject to JSON

The following code will serialize an instance of Person to JSON :

Person person;
person.setName("Flavio");
person.setPhoneNumber(123456);
person.setGender(Person::Male);
person.setDob(QDate(1982, 7, 12));

QVariantMap variant = QObjectHelper::qobject2qvariant(&person);
Serializer serializer;
qDebug() << serializer.serialize( variant);

The generated output will be:

{ "dob" : "1982-07-12", "gender" : 0, "name" : "Flavio", "phoneNumber" : 123456 }

From JSON to QObject

Suppose you have the following JSON data stored into a QString:

{ "dob" : "1982-07-12", "gender" : 0, "name" : "Flavio", "phoneNumber" : 123456 }

The following code will initialize an already allocated instance of Person using the JSON values:

Parser parser;
QVariant variant = parser.parse(json);

Person person;
QObjectHelper::qvariant2qobject(variant.toMap(), &person);

A new release

These changes have been included inside the new release of QJson: 0.7.0.

Packages for openSUSE are building right now.

I have just committed into trunk a couple of changes that make easier to serialize a QObject instance to JSON.

This solution relies on the awesome Qt’s property system.

Suppose the declaration of Person class looks like this:

class Person : public QObject
{
  Q_OBJECT

  Q_PROPERTY(QString name READ name WRITE setName)
  Q_PROPERTY(int phoneNumber READ phoneNumber WRITE setPhoneNumber)
  Q_PROPERTY(Gender gender READ gender WRITE setGender)
  Q_PROPERTY(QDate dob READ dob WRITE setDob)
  Q_ENUMS(Gender)

public:
    Person(QObject* parent = 0);
    ~Person();

    QString name() const;
    void setName(const QString& name);

    int phoneNumber() const;
    void setPhoneNumber(const int  phoneNumber);

    enum Gender {Male, Female};
    void setGender(Gender gender);
    Gender gender() const;

    QDate dob() const;
    void setDob(const QDate& dob);

  private:
    QString m_name;
    int m_phoneNumber;
    Gender m_gender;
    QDate m_dob;
};

The following code will serialize an instance of Person to JSON:

Person person;
person.setName("Flavio");
person.setPhoneNumber(123456);
person.setGender(Person::Male);
person.setDob(QDate(1982, 7, 12));

Serializer serializer;
qDebug() << serializer.serialize( &person);

The generated output will be:

{ "dob" : "1982-07-12", "gender" : 0, "name" : "Flavio", "phoneNumber" : 123456 }

I hope you will find this new feature useful. I'm also considering to create a similar method inside the Parser class.

As usual suggestions are welcome.

Some weeks have passed since the announcement of kaveau. I’m really proud and happy about this project because I received a lot of positive feedback messages and it has been chosen as one of the best Hackweek’s projects.

In the meantime I kept working on kaveau, so let me show you what has changed:

• rdiff-backup has been replaced by rsync.
• the setup wizard has been improved according to the feedback messages I received.
• old backups are now automatically removed.
• the code has been refactored a lot.

The switch to rsync

Previously kaveau used rdiff-backup as backup back-end. rdiff-backup is a great program but unfortunately it relies on the outdated librsync library. The latest release of librsync is dated 2004. It has a couple of serious bugs still open and, while rsync has reached version three, this library is still stuck at version one.

These are the reasons of the switch from rdiff-backup to rsync. This choice breaks the compatibility with the previous backups but it introduces a lot of advantages.
One of the most important improvements brought by the adoption of rsync is an easier restore procedure: now all the backups can be accessed using a standard file manager, while previously rdiff-backup was needed to access the old backups.

Backup directory structure

On the backup device everything is saved under the kaveau/hostname/username path.

The directory will have a similar structure:

drwxr-xr-x 3 flavio users 4096 2009-09-12 18:50 2009-09-12T18:50:19
drwxr-xr-x 3 flavio users 4096 2009-09-14 23:07 2009-09-14T23:07:46
drwxr-xr-x 3 flavio users 4096 2009-09-14 23:30 2009-09-14T23:30:36
lrwxrwxrwx 1 flavio users   19 2009-09-14 23:30 current -> 2009-09-14T23:30:36

As you can see there’s one directory per backup, plus a symlink called current pointing to the latest backup.

Old backup deletion

Nowadays big external storage devices are pretty cheap, but it’s always good to save some disk space.
Now kaveau keeps:

• hourly backups for the past 24 hours.
• daily backups for the past month.
• weekly backups until the external disk is full.

Thanks to hard links’ magic, old backups can be deleted without causing damages to the other ones.

Plans for the future

Before starting to work on the restore user interface I will spend some time figuring out how to add support for network devices.

A lot of users requested this feature, hence I want to make them happy .

I’m planning to use avahi to discover network shares (nfs, samba) or network machines running ssh and use them as backup devices. Honestly, I want to achieve something similar to Apple’s time capsule.

As usual, feedback messages are really appreciated.

Recently lots of people asked me how to build QJson under Windows. Most of them reported build/link errors, so I decided to try personally.

The good news is that QJson can be successfully built under Window, I can show you proof

I have written the build instructions on QJson website: just take a look here.

One last note: if you have problems with QJson please subscribe to the developer mailing list and post a message.

During the last week I had the possibility to work on anything I wanted, Novell’s hackweek is so cool

I decided to dedicate myself to an idea that has been obsessing me since a long time. Last December my brand new hard disk suddenly died, making impossible to recover anything. Fortunately I had just synchronized the most important documents between my workstation and my laptop, so I didn’t lose anything important. This incident make me realize that I should perform backups regularly and I immediately started looking for a good solution.

Personally I think that doing backups is pretty boring so I wanted something damned easy to setup and use. Something that once configured runs in the background and does the dirty job without bothering you. Let’s face the truth: I wanted Apple’s Time Machine for KDE.

After some searches I realized that nothing was fitting my requirements and I decided to create something new: kaveau.

What is kaveau?

Kaveau is a backup program that makes backup easy for the average user.

As you will see while coding/planning kaveau I made some assumptions and so only few things are configurable. I really think that sometimes “less is more”.

What does kaveau?

Current features:

• it performs backups to an external storage device: I don’t think it will ever store backup data on a remote host. If you want to do that just use some good project like Backup pc.
• it backs up the complete home directory of the user: storage is cheap and average users (like me) keep everything inside their home directory ( but it’s possible to exclude some directories from the backup).
• it performs incremental backups.
• the backup data are neither compressed nor stored in fancy formats: in this way you can plug your external disk into another machine and access your data without additional work.
• backups are performed automatically every hour (of course only if your external disk is plugged).
• notification messages are shown if your backup is older that a week.

More enhancements are coming…

What technologies does it use?

Backups are performed using rdiff-backup because it’s damned easy to use, well tested (it’s used also in production environments) and packaged by all distributions.

The awesome solid library is used for interacting with the external disks is super easy.

Status of kaveau

I have been working on kaveau just for five days, so there’s still a lot of work to do.

A screenshot tour will give you the right idea of its status.

Right now the code is available on this git repository but I don’t recommend you to try it (unless you want to find and fix bugs ).

I would really appreciate:

• feedback about the user interface (right now it looks too much like Time Machine).
• icons: it would be great to have a desktop icon and some system tray icons (contact me for more details).
• new code, bug fixes, code reviews, hints,…

Gran Canaria Desktop Summit has been great and really productive. I had the pleasure to meet people interested in QJson, chat with them but also hack with them.

In fact we hacked a lot, doing lots of changes to QJson:

• the API has been cleaned, now it can be considered stable
• unicode support has been completely rewritten
• it’s now possible to convert QVariant objects into JSON ones

So it’s with a great pleasure that I announce the release of QJson 0.6.0.

Beware, since the API has been changed your application will probably break. I’m really sorry about that, but I guarantee it won’t happen in the future (as I said both API and ABI interfaces can now be considered stable).

QJson web site has been updated, reflecting all the changes made to the library.
openSUSE packages has been moved from my home repo to KDE:Qt one.

One last note, if you have problems with QJson please contact me using the qjson-devel mailing list. You can subscribe here.

Now that I have booked both the flights and the hotel it’s official: I’ll attend the Gran Canaria Desktop Summit.

On Thursday 9th July I’ll give a BoF about QJson.

During the talk I will show:

• the advantages brought by QJson.
• the usage of QJson.
• some real programs using QJson.

See you soon!

During the last weekend I hacked a bit on rockmarble and I added a new feature: retrieve all the events happening in a certain city.

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During the last weekend I wanted to have some fun with QJson. So I came out with this idea: retrieve from last.fm the tour dates of my favourite artists and display the locations using Marble.

After some hacking I created this small application: rockmarble…

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