Export an Android SQLite db to an XML file on the SD Card

출처 :  http://mgmblog.com/2009/02/06/export-an-android-sqlite-db-to-an-xml-file-on-the-sd-card/ 

Export an Android SQLite db to an XML file on the SD Card

February 6th, 2009 in Android, Toolbox |

I’m pretty syched about this code.  It took some figuring out and some hunting and asking questions on Google’s Android forum.  But thanks to the following posts

 File permissions for world read/write

SQLite3 sql command to show tables in database

I pieced together the beginnings of some code that will take an Android SQLite db and export it to XML data within a file on the SD Card.  This has a couple potential uses,

• Backing up program data for importing later
• Archiving some of the data for an application for possible reprocessing later
• Archive some data to shrink the memory footprint of the application
• Export data to a web server
  • Data could be further broken down so only updated rows since last upload would be sent to server
• (fill in your idea here)

The code is still a little raw, not much error checking or exception handling, but I’m sure you can improve on it in those areas.  I just wanted to get it out so I didn’t have any more excuses.  The DatabaseAssistant class is called from your application and given the database to download.

Can anybody point out any obvious issues here (again, other then error/exception handling).  Hope you can make some use of it, sorry about the funky formatting, someday I’ll get around to a better way of adding code.

public class DatabaseAssistant
{
	private static final String EXPORT_FILE_NAME = "/sdcard/export.xml";

	private Context _ctx;
	private SQLiteDatabase _db;
	private Exporter _exporter;

	public DatabaseAssistant( Context ctx, SQLiteDatabase db )
	{
		_ctx = ctx;
		_db = db;

		try
		{
			// create a file on the sdcard to export the
			// database contents to
			File myFile = new File( EXPORT_FILE_NAME );
                        myFile.createNewFile();

                        FileOutputStream fOut =  new FileOutputStream(myFile);
                        BufferedOutputStream bos = new BufferedOutputStream( fOut );

			_exporter = new Exporter( bos );
		}
		catch (FileNotFoundException e)
		{
			e.printStackTrace();
		}
		catch (IOException e)
		{
			e.printStackTrace();
		}
	}

	public void exportData( )
	{
		log( "Exporting Data" );

		try
		{
			_exporter.startDbExport( _db.getPath() );

			// get the tables out of the given sqlite database
	    	        String sql = "SELECT * FROM sqlite_master";

	    	        Cursor cur = _db.rawQuery( sql, new String[0] );
	    	        Log.d("db", "show tables, cur size " + cur.getCount() );
	    	        cur.moveToFirst();

	    	        String tableName;
	    	        while ( cur.getPosition() < cur.getCount() )
	    	        {
	    		        tableName = cur.getString( cur.getColumnIndex( "name" ) );
	    		        log( "table name " + tableName );

	    		        // don't process these two tables since they are used
	    		        // for metadata
	    		        if ( ! tableName.equals( "android_metadata" ) &&
	    				! tableName.equals( "sqlite_sequence" ) )
	    		        {
	    			        exportTable( tableName );
	    		        }

	    		        cur.moveToNext();
	    	        }
		        _exporter.endDbExport();
			_exporter.close();
		}
		catch (IOException e)
		{
			e.printStackTrace();
		}
	}

	private void exportTable( String tableName ) throws IOException
	{
		_exporter.startTable(tableName);

		// get everything from the table
		String sql = "select * from " + tableName;
		Cursor cur = _db.rawQuery( sql, new String[0] );
		int numcols = cur.getColumnCount();

		log( "Start exporting table " + tableName );

//		// logging
//		for( int idx = 0; idx < numcols; idx++ )
//		{
//			log( "column " + cur.getColumnName(idx) );
//		}

		cur.moveToFirst();

		// move through the table, creating rows
		// and adding each column with name and value
		// to the row
		while( cur.getPosition() < cur.getCount() )
		{
			_exporter.startRow();
			String name;
			String val;
			for( int idx = 0; idx < numcols; idx++ )
			{
				name = cur.getColumnName(idx);
				val = cur.getString( idx );
				log( "col '" + name + "' -- val '" + val + "'" );

				_exporter.addColumn( name, val );
			}

			_exporter.endRow();
			cur.moveToNext();
		}

		cur.close();

		_exporter.endTable();
	}

	private void log( String msg )
	{
		Log.d( "DatabaseAssistant", msg );
	}

	class Exporter
	{
		private static final String CLOSING_WITH_TICK = "'>";
		private static final String START_DB = "<export-database name='";
		private static final String END_DB = "</export-database>";
		private static final String START_TABLE = "<table name='";
		private static final String END_TABLE = "</table>";
		private static final String START_ROW = "<row>";
		private static final String END_ROW = "</row>";
		private static final String START_COL = "<col name='";
		private static final String END_COL = "</col>";

		private BufferedOutputStream _bos;

		public Exporter() throws FileNotFoundException
		{
			this( new BufferedOutputStream(
					_ctx.openFileOutput( EXPORT_FILE_NAME,
					Context.MODE_WORLD_READABLE ) ) );
		}

		public Exporter( BufferedOutputStream bos )
		{
			_bos = bos;
		}

		public void close() throws IOException
		{
			if ( _bos != null )
			{
				_bos.close();
			}
		}

		public void startDbExport( String dbName ) throws IOException
		{
			String stg = START_DB + dbName + CLOSING_WITH_TICK;
			_bos.write( stg.getBytes() );
		}

		public void endDbExport() throws IOException
		{
			_bos.write( END_DB.getBytes() );
		}

		public void startTable( String tableName ) throws IOException
		{
			String stg = START_TABLE + tableName + CLOSING_WITH_TICK;
			_bos.write( stg.getBytes() );
		}

		public void endTable() throws IOException
		{
			_bos.write( END_TABLE.getBytes() );
		}

		public void startRow() throws IOException
		{
			_bos.write( START_ROW.getBytes() );
		}

		public void endRow() throws IOException
		{
			_bos.write( END_ROW.getBytes() );
		}

		public void addColumn( String name, String val ) throws IOException
		{
			String stg = START_COL + name + CLOSING_WITH_TICK + val + END_COL;
			_bos.write( stg.getBytes() );
		}
	}

	class Importer
	{

	}

}