Using Rowsets to Display Data - Java Database Programming Bible - page 440

Chapter 18: Using Rowsets to Display Data

In This Chapter

RowSets add significant new capabilities to JDBC by adding JavaBeans support to the JDBC API.
Rowsets make it easy to send tabular data over a network. They can also be used as a wrapper,
providing scrollable ResultSets or updatable ResultSets when the underlying JDBC driver does not
support them.

This chapter discusses RowSets , comparing them with the ResultSets of the JDBC core API and
illustrating the features of the different types of RowSets .

Understanding RowSets

A RowSet is an object that contains a set of rows from a ResultSet or some other source of tabular
data, like a file or spreadsheet. The RowSet object is an extension of ResultSet , with the added
benefit of incorporating JavaBeans support. The RowSet object is supported by the RowSetMetaData
interface, which extends the ResultSetMetaData interface.

A RowSet differs significantly from a ResultSet in that it provides a set of JavaBeans properties to
connect to a JDBC data source and to read data from the data source for making connections,
executing commands, and reading and writing data to and from the data source. These properties
include the following:

rowSet.setUrl( url );

rowSet.setUsername( login );

rowSet.setPassword( password );

rowSet.getConnection();

rowSet.setCommand("SELECT * FROM sysusers");

rowSet.execute();

Since RowSets are JavaBeans, notice that they follow the JavaBeans model for setting and getting
properties such as the Username and Password. They also follow the JavaBeans API to handle events
such as changes in a column value. Being JavaBeans, RowSets use the Java event model to notify
listeners when the RowSet is changed.

Rowsets make it easy to send tabular data over a network. They can also be used as a wrapper,
providing scrollable ResultSets or updatable ResultSets when the underlying JDBC driver does not
support them.

There are two main types of RowSets — connected and disconnected. A connected RowSet , like a
ResultSet , maintains a connection to a data source for as long as the RowSet is in use. A
disconnected RowSet gets a connection to a data source to load data or to propagate changes back to
the data source, but most of the time it does not have a connection open.

While it is disconnected, a RowSet does not need a JDBC driver or the full JDBC API, so its footprint is
very small. Since it is not continually connected to its data source, a disconnected RowSet stores its
data in memory. It also maintains metadata about the columns it contains and information about its
internal state.

Creating and Using a RowSet

The simplest way to explain how a RowSet works is to use an example. Listing 18-1 illustrates the use
of a JdbcRowSet to retrieve some names and e-mail addresses from the Contacts Table created as
part of the LEDES database in Chapter 2 .