Using RowSet Objects
RowSet object holds tabular data in a way that makes it more flexible and easier to use than a result set.
Oracle has defined five
RowSet interfaces for some of the more popular uses of a
RowSet, and standard reference are available for these
RowSet interfaces. In this tutorial you will learn how to use these reference implementations.
These versions of the
RowSet interface and their implementations have been provided as a convenience for programmers. Programmers are free to write their own versions of the
javax.sql.RowSet interface, to extend the implementations of the five
RowSet interfaces, or to write their own implementations. However, many programmers will probably find that the standard reference implementations already fit their needs and will use them as is.
This section introduces you to the
RowSet interface and the following interfaces that extend this interface:
The following topics are covered:
RowSet objects are derived from the
ResultSet interface and therefore share its capabilities. What makes JDBC
RowSet objects special is that they add these new capabilities:
RowSet objects are JavaBeans components. This means that they have the following:
- JavaBeans Notification Mechanism
RowSet objects have properties. A property is a field that has corresponding getter and setter methods. Properties are exposed to builder tools (such as those that come with the IDEs JDveloper and Eclipse) that enable you to visually manipulate beans. For more information, see the Properties lesson in the JavaBeans trail.
JavaBeans Notification Mechanism
RowSet objects use the JavaBeans event model, in which registered components are notified when certain events occur. For all
RowSet objects, three events trigger notifications:
- A cursor movement
- The update, insertion, or deletion of a row
- A change to the entire
The notification of an event goes to all listeners, components that have implemented the
RowSetListener interface and have had themselves added to the
RowSet object's list of components to be notified when any of the three events occurs.
A listener could be a GUI component such as a bar graph. If the bar graph is tracking data in a
RowSet object, the listener would want to know the new data values whenever the data changed. The listener would therefore implement the
RowSetListener methods to define what it will do when a particular event occurs. Then the listener also must be added to the
RowSet object's list of listeners. The following line of code registers the bar graph component
bg with the
bg will be notified each time the cursor moves, a row is changed, or all of
rs gets new data.
Some DBMSs do not support result sets that can be scrolled (scrollable), and some do not support result sets that can be updated (updatable). If a driver for that DBMS does not add the ability to scroll or update result sets, you can use a
RowSet object to do it. A
RowSet object is scrollable and updatable by default, so by populating a
RowSet object with the contents of a result set, you can effectively make the result set scrollable and updatable.
RowSet object is considered either connected or disconnected. A connected
RowSet object uses a JDBC driver to make a connection to a relational database and maintains that connection throughout its life span. A disconnected
RowSet object makes a connection to a data source only to read in data from a
ResultSet object or to write data back to the data source. After reading data from or writing data to its data source, the
RowSet object disconnects from it, thus becoming "disconnected." During much of its life span, a disconnected
RowSet object has no connection to its data source and operates independently. The next two sections tell you what being connected or disconnected means in terms of what a
RowSet object can do.
Connected RowSet Objects
Only one of the standard
RowSet implementations is a connected
JdbcRowSet. Always being connected to a database, a
JdbcRowSet object is most similar to a
ResultSet object and is often used as a wrapper to make an otherwise non-scrollable and read-only
ResultSet object scrollable and updatable.
As a JavaBeans component, a
JdbcRowSet object can be used, for example, in a GUI tool to select a JDBC driver. A
JdbcRowSet object can be used this way because it is effectively a wrapper for the driver that obtained its connection to the database.
Disconnected RowSet Objects
The other four implementations are disconnected
RowSet implementations. Disconnected
RowSet objects have all the capabilities of connected
RowSet objects plus they have the additional capabilities available only to disconnected
RowSet objects. For example, not having to maintain a connection to a data source makes disconnected
RowSet objects far more lightweight than a
JdbcRowSet object or a
ResultSet object. Disconnected
RowSet objects are also serializable, and the combination of being both serializable and lightweight makes them ideal for sending data over a network. They can even be used for sending data to thin clients such as PDAs and mobile phones.
CachedRowSet interface defines the basic capabilities available to all disconnected
RowSet objects. The other three are extensions of the
CachedRowSet interface, which provide more specialized capabilities. The following information shows how they are related:
CachedRowSet object has all the capabilities of a
JdbcRowSet object plus it can also do the following:
- Obtain a connection to a data source and execute a query
- Read the data from the resulting
ResultSetobject and populate itself with that data
- Manipulate data and make changes to data while it is disconnected
- Reconnect to the data source to write changes back to it
- Check for conflicts with the data source and resolve those conflicts
WebRowSet object has all the capabilities of a
CachedRowSet object plus it can also do the following:
- Write itself as an XML document
- Read an XML document that describes a
JoinRowSet object has all the capabilities of a
WebRowSet object (and therefore also those of a
CachedRowSet object) plus it can also do the following:
- Form the equivalent of a
SQL JOINwithout having to connect to a data source
FilteredRowSet object likewise has all the capabilities of a
WebRowSet object (and therefore also a
CachedRowSet object) plus it can also do the following:
- Apply filtering criteria so that only selected data is visible. This is equivalent to executing a query on a
RowSetobject without having to use a query language or connect to a data source.