Java Reference
In-Depth Information
ResultSetTableModel
object and the GUI for the application and displays the GUI in a
JFrame
. Line 64 creates the
JTable
object and passes a
ResultSetTableModel
object (cre-
ated at lines 42-43) to the
JTable
constructor, which then registers the
JTable
as a listener
for
TableModelEvent
s generated by the
ResultSetTableModel
.
The local variables
queryArea
(line 46),
filterText
(line 67) and
sorter
(lines 121-
122) are declared
final
because they're used from anonymous inner classes. Recall that
any local variable that will be used in an anonymous inner class must be declared
final
;
otherwise, a compilation error occurs. (In Java SE 8, this program would compile without
declaring these variables
final
because these variables would be effectively
final
, as dis-
cussed in Chapter 17.)
Lines 82-119 register an event handler for the
submitButton
that the user clicks to
submit a query to the database. When the user clicks the button, method
actionPer-
formed
(lines 85-117) invokes method
setQuery
from the class
ResultSetTableModel
to
execute the new query (line 90). If the user's query fails (e.g., because of a syntax error in
the user's input), lines 102-103 execute the default query. If the default query also fails,
there could be a more serious error, so line 112 ensures that the database connection is
closed and line 114 exits the program. The screen captures in Fig. 24.28 show the results
of two queries. The first screen capture shows the default query that retrieves all the data
from table
Authors
of database
books
. The second screen capture shows a query that
selects each author's first name and last name from the
Authors
table and combines that
information with the title and edition number from the
Titles
table. Try entering your
own queries in the text area and clicking the
Submit Query
button to execute the query.
Lines 161-170 register a
WindowListener
for the
windowClosed
event, which occurs
when the user closes the window. Since
WindowListener
s can handle several window
events, we extend class
WindowAdapter
and override only the
windowClosed
event handler.
Sorting Rows in a
JTable
JTable
s allow users to sort rows by the data in a specific column. Lines 121-122 use the
TableRowSorter
class (from package
javax.swing.table
) to create an object that uses our
ResultSetTableModel
to sort rows in the
JTable
that displays query results. When the
user clicks the title of a particular
JTable
column, the
TableRowSorter
interacts with the
underlying
TableModel
to reorder the rows based on the data in that column. Line 123
uses
JTable
method
setRowSorter
to specify the
TableRowSorter
for
resultTable
.
Filtering Rows in a
JTable
JTable
s can now show subsets of the data from the underlying
TableModel
. This is known
as filtering the data. Lines 126-152 register an event handler for the
filterButton
that
the user clicks to filter the data. In method
actionPerformed
(lines 130-150), line 132
obtains the filter text. If the user did not specify filter text, line 135 uses
JTable
method
setRowFilter
to remove any prior filter by setting the filter to
null
. Otherwise, lines 140-
141 use
setRowFilter
to specify a
RowFilter
(from package
javax.swing
) based on the
user's input. Class
RowFilter
provides several methods for creating filters. The
static
method
regexFilter
receives a
String
containing a regular expression pattern as its argu-
ment and an optional set of indices that specify which columns to filter. If no indices are
specified, then all the columns are searched. In this example, the regular expression pattern
is the text the user typed. Once the filter is set, the data displayed in the
JTable
is updated
based on the filtered
TableModel
.
