Tuesday Sep 15, 2009

JavaFX - Custom Feed Parsers


In one of my previous post I have described the use of RSS and ATOM Task to parse the feeds.

Unfortunately many feeds do not strictly comply with the RSS/ATOM format. Example: In some cases the date specified for pubDate element may be in wrong format, or its an invalid date or the information specified is embedded in CDATA instead of TEXT. The parser will fail for such scenarios. Hence we need to implement custom parsers so as to handle the situation.

Below sample reads engadget rss feed..

<script src="http://dl.javafx.com/1.2/dtfx.js"></script><script src="/rakeshmenonp/resource/CustomRssTask/CustomRssTask.js"></script>

For Applet mode, click on above image

Both RssTask and AtomTask API provide an attribute - factory - which can be used to specify custom implementation of RSS or ATOM Factory. Users may also customize various elements such as Channel, Item, Entry, Feed by overriding functions such as - fromXML, tryParseDate etc.

Example: In some cases the default parser fails to convert pubDate to valid DateTime instance. So a new attribute - pubDateText - is added so as to save the date as String.

/\*\*
 \* Customize Item so as to override fromXML
 \*/
class CustomItem extends Item {
    
    public-read var pubDateText : String;
    
    override function fromXML(parser: PullParser): Void {
        
        if(parser.event.qname == PUB_DATE) {
            if ((parser.event.type == PullParser.TEXTor
                (parser.event.type == PullParser.CDATA)) {
                pubDateText = stripCDATA(parser.event.text)
            }
        else if(parser.event.qname == TITLE) {
            title = stripCDATA(parser.event.text);
        else {
            super.fromXML(parser);
        }
    }
}

Now we need to implement a custom Factory which will instantiate and return the above CustomItem instance.

/\*\*
 \* Customize Factory so as to return CustomItem
 \*/
class CustomFactory extends Factory {
    public override function newItem(c: Channel: Item {
        CustomItem parent: c channel: c }
    }
}

Above Factory is set in factory attribute of RssTask as shown below.

var rssTask = RssTask {

    // set custom factory
    factory: CustomFactory { }

    location: "http://www.engadget.com/rss.xml"
    onChannel: function(channel) {  }
    onItem: function(item) { }
}
rssTask.start();

Update: Please refer to SpeedReaderFX by Jim Weaver for real world example.

Try it out and let me know feedback


<script type="text/javascript">var dzone_style = '2';</script> <script language="javascript" src="/rakeshmenonp/resource/CustomRssTask/zoneit.js"></script>

Thursday Jun 18, 2009

JavaFX - RSS and ATOM Task


JavaFX 1.2 provides new APIs to handle RSS and ATOM feeds. RssTask and AtomTask parses the feeds and provide the content as JavaFX objects. It can also be configured to provide updates on regular intervals.

RssTask parses the feed and provides the content as Channel and Item objects. These objects in-turn provides other information such as image, link, title, category, date etc.

Similarly AtomTask parses feed and provides Feed and Entry objects. These objects in-turn provides information such as author, category, link, logo, contributors etc.

News ticker using Yahoo RSS feed is given below.

<script src="http://dl.javafx.com/1.2/dtfx.js"></script><script src="/rakeshmenonp/resource/RssAtom/RssAtom.js"></script>

For Applet mode, click on above image

For standalone mode

RssTask Usage:

var rssTask = RssTask {
    
    location: "http://rss.news.yahoo.com/rss/world"
    interval: 300s

    onException: function(e) {
        e.printStackTrace();
    }

    onChannel: function(channel) {
        println("{channel.title}");
    }

    onItem: function(item) {
        println("{item.title}");
    }
}
rssTask.start();

AtomTask Usage:

var atomTask = AtomTask {
    
    location: "http://jfxstudio.wordpress.com/feed/atom"
    interval: 300s

    onException: function(e) {
        e.printStackTrace();
    }

    onFeed: function(feed) {
        println("{feed.title}");
    }

    onEntry: function(entry) {
        println("{entry.title}");        
    }
}
atomTask.start();

JavaFX Tweeter sample demonstrates use of both RssTask and HttpRequest.

Source:

<script type="text/javascript">var dzone_url = "http://blogs.sun.com/rakeshmenonp/entry/javafx_rss_and_atom_task";</script> <script type="text/javascript">var dzone_style = '2';</script> <script language="javascript" src="http://widgets.dzone.com/widgets/zoneit.js"></script>

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