ORMLite

After finishing creating everything with generic classes, I was trying to upgrade my design, so that the developer could create multiple tables and relations between them. While documenting, I walked into ORMLite. This is the ORM for SQLite. I found it so easy to use and developer friendly, that I thought of giving it a try.

You can add it very easily to your project - just download the 2 needed jars from ormlite.com (ormlite-core.jar and ormlite-android.jar - version 4.39 at the time of this post) and everything will work like a charm. What you need to do is Annotate your Classes using ORMLite Annotations or javax.persistence Annotations. The next step is to configure a DAO, but for more examples and information use this link.

What got me thinking about ORMLite is the size of it - approximately 250KB. Since I don't really need all the options that ORMLite offers, I started working on my own ORM (very simple one). I created some custom Annotations for my classes, but what I am working now on is dealing with Content Provider, which is mostly used with databases with single tables, and even if you have multiple tables, the most common way to distinguish between them is through URIs. I cannot do this, because I only have the name and number of the tables at run-time, when the Content Provider has already been initialized.

Currently I can create the query for creating a new table, but I don't get the chance to use it. I will write in the future about the solution I found. I hope I will find something better than rawQuery.

The steps I want to follow in the near future are:

• Update the Content Provider so that it can work with multiple tables 
• create tables at run-time
• update the needed URIs used in Content Provider
• Use C2DM to update the SQLite database. Currently I am only receiving "Hello world" messages from the server. 

Future requirements - API

I was preoccupied by the graphics of the application, although this was not the main idea behind this project. I should focus more on creating the needed API, than some fancy application. The developer using my API should be able to create, read, update and delete some data from the SQLite Database, and the backup to Google App Engine will be made transparently by the API.

So I created a new application, which simulates the creation of a developer and uses it to back everything up to Google App Engine. I use Generic Classes, so no matter what fields the developer's class will have, everything will work just fine. I do this by creating a JSON file with the fields of the class:

private <T> String createJsonFile(Class<T> Kind) {
    String json;

    /*Get all fields, including the private ones*/
    Field[] fields = Kind.getDeclaredFields();
    int fieldsNo = fields.length;

    /*For each field, add to the JSON String the field's name*/
    for (Field field : fields) {
        fieldsNo--;
        json += "\"" + field.getName() + "\"";
        if (fieldsNo != 0)
            json += ",";
    }
    return json;
}

So these are the steps that I should follow while redesigning the application:

• Create JSON file from Class.
• Create SQLite Database with this structure (the table should have the same fields).
• Update the server concerning the schema.
• POST the JSON file
• Add one item to SQLite Database.
• Read/Modify/Delete items from SQLite Database.
• Synchronize the server when needed. 

These are small steps which I began already to implement. The last step can be further divided into smaller steps, but this is what I plan for now. It shouldn't be to difficult to implement, considering that most of it I already have, but I need to reorganize things.

An image with how should all look like is this one: