datasource.as

用于flash/flex的 as3的 2D图形图像图表的动态生成

package flare.data
{
	import flash.net.URLRequest;
	import flash.net.URLStream;
	import flash.utils.IDataInput;
	import flare.data.converters.IDataConverter;
	import flash.net.URLLoader;
	import flash.events.Event;
	import flare.data.converters.Converters;
	import flash.utils.ByteArray;
	import flash.net.URLLoaderDataFormat;
	import flash.events.ProgressEvent;
	
	/**
	 * A data source provides access to remote data on the Internet.
	 * A DataSource requires a URL for retrieving a data file, and a format
	 * string representing the data format. The currently supported formats are
	 * "tab" (Tab-Delimited Text) and "json" (JavaScript Object Notation).
	 * Additionally, a DataSource can be given a schema object describing the
	 * data fields and their types (int, Number, Date, String, etc). If no
	 * schema is provided, the data converter for the particular format will
	 * attempt to infer the data types directly from the data itself.
	 * 
	 * <p>Once a DataSource has been created, use the <tt>load</tt> method to
	 * initiate data loading. This method returns a <tt>URLLoader</tt> 
	 * instance. Add a listener to the URLLoader's COMPLETE event to be
	 * notified when loading and parsing has been completed. When a COMPLETE
	 * event is issued, the URLLoader's <tt>data</tt> property will contain the
	 * loaded and parsed data set.</p>
	 */
	public class DataSource
	{
		private var _url:String;
		private var _format:String;
		private var _schema:DataSchema;
		
		/** The URL of the remote data set. */
		public function get url():String { return _url; }
		/** The format of the remote data set (e.g., "tab" or "json"). */
		public function get format():String { return _format; }
		/** A schema describing the attributes of the data set. */
		public function get schema():DataSchema { return _schema; }
		
		/**
		 * Creates a new DataSource.
		 * @param url the URL of the remote data set
		 * @param format the format of the remote data set (e.g., "tab" or
		 *  "json")
		 * @param schema an optional schema describing the attibutes of the
		 *  data set
		 */
		public function DataSource(url:String, format:String, schema:DataSchema=null)
		{
			_url = url;
			_format = format;
			_schema = schema;
		}
		
		/**
		 * Initiates loading of the data set. When the load completes, a data
		 * converter instance is used to convert the retrieved data set into
		 * ActionScript objects. The parsed data is then available through the
		 * <code>data</code> property of the returned <code>URLLoader</code>.
		 * @return a URLLoader instance responsible for loading the data set.
		 *  Add an event listener for the <code>COMPLETE</code> event to be
		 *  notified when data loading has completed.
		 */
		public function load():URLLoader
		{
			var loader:URLLoader = new URLLoader();
			loader.dataFormat = URLLoaderDataFormat.BINARY;
			loader.addEventListener(Event.COMPLETE,
				function(evt:Event):void {
					var conv:IDataConverter = Converters.lookup(_format);
					loader.data = conv.read(loader.data, _schema);
				}
			);
			loader.load(new URLRequest(_url));
			return loader;
		}
		
		/* TODO later -- support streaming data
		public function stream():URLStream
		{
			
		}
		*/
		
	} // end of class DataSource
}