A RowSet is an object that encapsulates a set of rows retrieved from a database or other tabular data store, such as a spreadsheet. To implement a RowSet, your code must import javax.sql, and implement the RowSet interface. RowSet extends the java.sql.ResultSet interface, permitting it to act as a JavaBeans component.

• You can create NAS-dependent code by calling new on the NASRowSet class:

NASRowSet rs = new NASRowSet();

• You can create NAS-independent code. To do so, call new on the InitialContext class. Then, using this InitialContext, look up the class that implements the RowSet interface:

InitialContext ctx = new InitialContext();
RowSet rs = (javax.sql.RowSet) ctx.lookup("javax.sql.RowSet");

• The ctx.lookup( ) call returns an instance of the class that is bound to the implementation of javax.sql.RowSet. In this case, the class that is bound is NASRowSet.

• implements, in whole or in part, these four standard interfaces:

• javax.sql.RowSet
• javax.sql.RowSetReader
• javax.sql.RowSetWriter
• javax.sql.RowSetInternal
• implements many methods available in CachedRowSet, a class provided by Sun.
• implements loadQuery( ), a method of the SqlUtil class in the com.kivasoft.util package.

The RowSet interface is fully supported except as noted in the following table:

NASRowSet provides a full implementation of the RowSetReader interface. As an alternative to one of the RowSetReader methods, you can use the setReaderMethod( ) from the CachedRowSet class. The argument of setReaderMethod( ) must nonetheless implement the RowSetReader interface.

Although NASRowSet is read-only, it implements the RowSetWriter interface for future use. The only method of RowSetWriter, writeData( ), throws SQLException when called, indicating that this method is not supported.

This internal interface is called by a method of the RowSetReader interface to retrieve information about the RowSet. RowSetInternal has a single method, getOriginalRow( ), which returns the entire result set instead of a single row.

Sun provides a rowset class named CachedRowSet, which is an implementation of the RowSet interface. CachedRowSet lets you retrieve data from a data source, then detach from the data source while you examine (and modify) the data. A cached rowset keeps track of not only the original data retrieved, but also any data changes your application made. If the application trys to update the original data source, the rowset is reconnected to the data source, and only those rows that have changed are merged back into the database.

• acceptChanges( )
• cancelRowDelete( )
• cancelRowInsert( )
• getShowDeleted( )
• restoreOriginal( )
• setShowDeleted( )
• setWriter( )

The SqlUtil class is part of the NAS Foundation Class Library. This class contains loadQuery( ), a method that supports rowsets. The loadQuery( ) method can be used on the RowSet interface in place of the setCommand( ) method.

import com.kivasoft.util.SqlUtil;

...

SqlUtil.loadQuery(rowset, pathname, queryname, params);