Thursday, 20 November 2008

Read and write to .properties and .ini files

It is usual to store settings or properties of an application in some of these 5 known ways:

- to DB
- to XML
- to .ini file
- to .properties file
- to registry

My favorite are XML and .ini/.properties file.
All of them has some kind of restrictions, and it’s really up to data type that application needs to save , and which programming language I’m using at that moment…

If my application needs to read/save small number of information, without complex scheme of sections, then I always use .properties or .ini files.

To be honest, first time I used ( Java )class that works with .properties files, I was very surprised how easy is it to read/write settings. And all of that with small-size code, which is not usual in Java. ( Look at my earlier blog about parsing a document in PHP and Java : )

In Java, in order to work with .properties files, there’s a Properties class. Properties class extends HashTable , so we manipulate properties through the get and set methods.
It’s quite easy and fun to work with it.
Let’s say we have some file:, and it looks something like this:

We could easily parse it like this:
or, write current properties in application into the file with:

If we write

public static void main(String args[])
Main main = new Main();

the result would be:

color= blue
width= 150
height= 100
color= blue width= 150 height= 100
The other way around, if we write

public static void main(String args[])
Main main = new Main();

the file would look like this:
but, as you can see, without any particular order among properties that we wrote.

As I sad, I didn’t used to write something in Java with such small code size, and it feels great… :-)

All of this reminds me of TIniFile class in Borland Builder, and it is very hard to catch up with BCB when it comes to simplicity ( in my opinion, that is…).

Let’s take a look how we would do this in BCB. Ini files are very similar to .properties files. The difference is that .ini files have sections, and .properties doesn’t.

Let’s make a test application:
and let’s say we have file example.ini with a "data" section, and is looks something like this:
and we need to write these settings in appropriate Edits on the Form when someone starts the application. At exit, we need to overwrite properties in a file with those that are in these three Edits at that moment…

First of all, we would need this line:

Then, we could easily parse the document with:

or, write current properties in application into the file with:

If we write a constructor and a FormClose event like this:
__fastcall TForm1::TForm1(TComponent* Owner)
: TForm(Owner)

void __fastcall TForm1::FormClose(TObject *Sender, TCloseAction &Action)

and we start the app, it will read properties from ini file, and show it.

and , if we write some other values, then the FormClose event will write new values to the ini file, preserving the order that we wanted...

So, you saw now how easy it is to save properties into these two formats. I hope you like it the way I do...

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