Because database access is inherently asynchronous, you’ll surely want to retrieve rows in the background to avoid blocking the event dispatch thread; SwingWorker makes this relatively easy. Fetch rows in your implementation of doInBackground(), publish() interim results, and add them to the table model in your implementation of process(). A complete example that outlines the attendant benefits is shown here. The example loops through a file, but you can substitute your ResultSet operations.
while (rs.next()) {
//collect row data
publish(rowData);
}
Defer tableData.add() to your implementation of process().
Focusing on the interaction between the custom TableModel and its contained SwingWorker, the following complete example creates a test database having N rows and displays a JTable showing the results of a query of that table. In particular,
-
JDBCModelextendsAbstractTableModel. For simplicity, the model’sdatais stored in aList<Row>, andResultSetMetaDatais used for the column names. As a more abstract alternative, see Apache CommonsDbUtils, which uses Class Literals as Runtime-Type Tokens andResultSetMetaDatato safely create instances of row data. -
JDBCModeldelegates row retrieval to a privateJDBCWorker; it invokespublish()on each row retrieved from theResultSet; becauseprocess()runs on the EDT, the worker can optimize the number of table model events that it fires on behalf of the parent model usingfireTableRowsInserted(). -
Similarly, your implementation of
delete()should reside inJDBCModel, not the GUI; it shouldfireTableRowsDeleted()after the row is successfully deleted from the database and removed fromdata. -
Add
Thread.sleep()to the worker’s background loop to see the effect of artificially increasing latency. -
Use
setProgress()and aPropertyChangeListener, shown here, to display progress; aJOptionPanewhendone()may be superfluous. -
Override
getPreferredScrollableViewportSize()to customize the size of the table’s enclosingJScrollPane. -
Avoid class names, e.g.
TableModel, that collide with common API names. -
A variation that implements live filtering in the view is examined here.
import java.awt.Dimension;
import java.awt.EventQueue;
import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.SQLException;
import java.sql.Statement;
import java.util.ArrayList;
import java.util.List;
import java.util.Random;
import javax.swing.JFrame;
import javax.swing.JScrollPane;
import javax.swing.JTable;
import javax.swing.SwingWorker;
import javax.swing.table.AbstractTableModel;
/**
* @see https://stackoverflow.com/a/34742409/230513
* @see https://stackoverflow.com/a/24762078/230513
*/
public class WorkerTest {
private static final int N = 1_000;
private static final String URL = "jdbc:h2:mem:test";
private static final Random r = new Random();
private void display() {
JFrame f = new JFrame("WorkerTest");
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
createTestDatabase(N);
JDBCModel model = new JDBCModel(getConnection(), "select * from city");
f.add(new JScrollPane(new JTable(model) {
@Override
public Dimension getPreferredScrollableViewportSize() {
return new Dimension(320, 240);
}
}));
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
}
private static class Row {
int ID;
String name;
}
private static class JDBCModel extends AbstractTableModel {
private final List<Row> data = new ArrayList<>();
private ResultSet rs = null;
private ResultSetMetaData meta;
public JDBCModel(Connection conn, String query) {
try {
Statement s = conn.createStatement();
rs = s.executeQuery(query);
meta = rs.getMetaData();
JDBCWorker worker = new JDBCWorker();
worker.execute();
} catch (SQLException e) {
e.printStackTrace(System.err);
}
}
@Override
public int getRowCount() {
return data.size();
}
@Override
public int getColumnCount() {
try {
return meta.getColumnCount();
} catch (SQLException e) {
e.printStackTrace(System.err);
}
return 0;
}
@Override
public Object getValueAt(int rowIndex, int colIndex) {
Row row = data.get(rowIndex);
switch (colIndex) {
case 0:
return row.ID;
case 1:
return row.name;
}
return null;
}
@Override
public String getColumnName(int colIndex) {
try {
return meta.getColumnName(colIndex + 1);
} catch (SQLException e) {
e.printStackTrace(System.err);
}
return null;
}
private class JDBCWorker extends SwingWorker<List<Row>, Row> {
@Override
protected List<Row> doInBackground() {
try {
while (rs.next()) {
Row r = new Row();
r.ID = rs.getInt(1);
r.name = rs.getString(2);
publish(r);
}
} catch (SQLException e) {
e.printStackTrace(System.err);
}
return data;
}
@Override
protected void process(List<Row> chunks) {
int n = getRowCount();
for (Row row : chunks) {
data.add(row);
}
fireTableRowsInserted(n, n + chunks.size());
}
}
}
private static void createTestDatabase(int n) {
Connection conn = getConnection();
try {
Statement st = conn.createStatement();
st.execute("create table city(id integer, name varchar2)");
PreparedStatement ps = conn.prepareStatement(
"insert into city values (?, ?)");
for (int i = 0; i < n; i++) {
ps.setInt(1, i);
ps.setString(2, (char) ('A' + r.nextInt(26))
+ String.valueOf(r.nextInt(1_000_000)));
ps.execute();
}
} catch (SQLException ex) {
ex.printStackTrace(System.err);
}
}
private static Connection getConnection() {
try {
return DriverManager.getConnection(URL, "", "");
} catch (SQLException e) {
e.printStackTrace(System.err);
}
return null;
}
public static void main(String[] args) {
EventQueue.invokeLater(new WorkerTest()::display);
}
}