A JDBC
Oracle has defined five
These versions of the
This section introduces you to the
The following topics are covered:
The notification of an event goes to all listeners, components that have implemented the
A listener could be a GUI component such as a bar graph. If the bar graph is tracking data in a
The following line of code registers the bar graph component
rs.addListener(bg);
Now
If a driver for that DBMS does not add the ability to scroll or update result sets, you can use a
A disconnected
The next two sections tell you what being connected or disconnected means in terms of what a
As a JavaBeans component, a
Disconnected
The
A
A
A
A
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 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:JdbcRowSet
CachedRowSet
WebRowSet
JoinRowSet
FilteredRowSet
- What Can RowSet Objects Do?
- Kinds of RowSet Objects
What Can RowSet Objects Do?
AllRowSet
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:- Function as JavaBeans Component
- Add Scrollability or Updatability
Function as JavaBeans Component
AllRowSet
objects are JavaBeans components. This means that they have the following:- Properties
- JavaBeans Notification Mechanism
Properties
AllRowSet
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.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
RowSet
contents
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 RowSet
object rs
.rs.addListener(bg);
Now
bg
will be notified each time the cursor moves, a row is changed, or all of rs
gets new data.Add Scrollability or Updatability
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.Kinds of RowSet Objects
ARowSet
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 standardRowSet
implementations is a connected RowSet
object: 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 disconnectedRowSet
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.The
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:A
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
ResultSet
object 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
A
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
WebRowSet
object
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 JOIN
without having to connect to a data source
A
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
RowSet
object without having to use a query language or connect to a data source.
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