Data Crawler

TODO: is the scan() method asynchronously? If yes, then it would return immediatly to the caller and the current status of this object is needed to be accessible throug a getScanStatus() method, returning either idle, scanning, tryingtostopscanning or stopped. If not, why the funny Exit codes?

Java Interface

Probably equal to:

• source:trunk/gnowsis/src/org/gnowsis/data/structured/StructuredAdapter.java and
• source:trunk/gnoDesktopSearch/src/java/org/gnowsis/desktopsearch/crawler

and probably merge:

• biz.aduna.datasource.crawler.DataCrawlerListener with
• source:/trunk/gnoDesktopSearch/src/java/org/gnowsis/desktopsearch/crawler/CrawlerListener.java

/**
 * A DataCrawler accesses the physical source represented by a DataSource
 * and delivers a stream of DataObjects representing the individual items
 * in that source.  To access the DataObjects, the DataCrawler itself
 * will use DataAccessor objects.
 */
public interface DataCrawler {
        
        /**
         * Constants used to indicate why a scan was stopped.
         */
        public static enum ExitCode {
                COMPLETED,        // the scan procedure terminated normally
                BY_REQUEST,       // the DataCrawler was requested to abort the scan procedure
                FATAL_EXCEPTION   // an error occurred that made further scanning impossible
        };
        
        /**
         * Returns the DataSource crawler by this DataCrawler.
         */
        public DataSource getDataSource();
    
        /**
         * Starts a scan for DataObjects over the configured domain defined
         * in the DataSource. If this is not the first run of this DataCrawler,
         * it will only report the differences with the previous run, unless the
         * previous scan results have been cleared.
         **/
        public void scan();

        /**
         * Stops a running scan operation as fast as possible. This method
         * may return before the operation has actually been stopped.
         **/
        public void stopScanning();

        /**
         * Clears all stored scan results. Any listeners registered with
         * this data source will be notified of the removal of the data
         * objects. The next call to scan() will again report all
         * data objects in the configured domain.
         **/
        public void clearScanResults();

        /**
         * Gets the ScanReport of the last performed scan, or the current
         * scan when a scan is in progress. Returns null when
         * no scan was performed in this session and there is no scan report
         * available from the previous session.
         * 
         * @return The ScanReport of the last session, or null when
         * this is not available.
         **/
        public ScanReport getLastScanReport();
        
        /**
         * Adds a DataSourceListener to which this data source should
         * report any scanned or cleared data objects.
         *
         * @param listener The DataCrawlerListener to add.
         **/
        public void addListener(DataCrawlerListener listener);

        /**
         * Removes a DataSourceListener from this data source.
         *
         * @param listener The DataCrawlerListener to remove.
         **/
        public void removeListener(DataCrawlerListener listener);
}