The standard interface that all standard implementations of
JdbcRowSet must implement.
1.0 Overview
A wrapper around a ResultSet object that makes it possible
to use the result set as a JavaBeansTM
component. Thus, a JdbcRowSet object can be one of the Beans that
a tool makes available for composing an application. Because
a JdbcRowSet is a connected rowset, that is, it continually
maintains its connection to a database using a JDBC technology-enabled
driver, it also effectively makes the driver a JavaBeans component.
Because it is always connected to its database, an instance of
JdbcRowSet
can simply take calls invoked on it and in turn call them on its
ResultSet object. As a consequence, a result set can, for
example, be a component in a Swing application.
Another advantage of a JdbcRowSet object is that it can be
used to make a ResultSet object scrollable and updatable. All
RowSet objects are by default scrollable and updatable. If
the driver and database being used do not support scrolling and/or updating
of result sets, an application can populate a JdbcRowSet object
with the data of a ResultSet object and then operate on the
JdbcRowSet object as if it were the ResultSet
object.
2.0 Creating a JdbcRowSet Object
The reference implementation of the JdbcRowSet interface,
JdbcRowSetImpl, provides an implementation of
the default constructor. A new instance is initialized with
default values, which can be set with new values as needed. A
new instance is not really functional until its execute
method is called. In general, this method does the following:
- establishes a connection with a database
- creates a
PreparedStatement object and sets any of its
placeholder parameters
- executes the statement to create a
ResultSet object
If the execute method is successful, it will set the
appropriate private JdbcRowSet fields with the following:
- a
Connection object -- the connection between the rowset
and the database
- a
PreparedStatement object -- the query that produces
the result set
- a
ResultSet object -- the result set that the rowset's
command produced and that is being made, in effect, a JavaBeans
component
If these fields have not been set, meaning that the execute
method has not executed successfully, no methods other than
execute and close may be called on the
rowset. All other public methods will throw an exception.
Before calling the execute method, however, the command
and properties needed for establishing a connection must be set.
The following code fragment creates a JdbcRowSetImpl object,
sets the command and connection properties, sets the placeholder parameter,
and then invokes the method execute.
JdbcRowSetImpl jrs = new JdbcRowSetImpl();
jrs.setCommand("SELECT * FROM TITLES WHERE TYPE = ?");
jrs.setURL("jdbc:myDriver:myAttribute");
jrs.setUsername("cervantes");
jrs.setPassword("sancho");
jrs.setString(1, "BIOGRAPHY");
jrs.execute();
The variable jrs now represents an instance of
JdbcRowSetImpl that is a thin wrapper around the
ResultSet object containing all the rows in the
table TITLES where the type of book is biography.
At this point, operations called on jrs will
affect the rows in the result set, which is effectively a JavaBeans
component.
The implementation of the RowSet method execute in the
JdbcRowSet reference implementation differs from that in the
CachedRowSetTM
reference implementation to account for the different
requirements of connected and disconnected RowSet objects.
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