Java tutorial
/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
import java.sql.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import javax.swing.*;
/**
* This program demonstrates several complex database queries.
* @version 1.23 2007-06-28
* @author Cay Horstmann
*/
public class QueryDB
{
public static void main(String[] args)
{
EventQueue.invokeLater(new Runnable()
{
public void run()
{
JFrame frame = new QueryDBFrame();
frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
frame.setVisible(true);
}
});
}
}
/**
* This frame displays combo boxes for query parameters, a text area for command results, and
* buttons to launch a query and an update.
*/
class QueryDBFrame extends JFrame {
public QueryDBFrame() {
setTitle("QueryDB");
setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
setLayout(new GridBagLayout());
authors = new JComboBox();
authors.setEditable(false);
authors.addItem("Any");
publishers = new JComboBox();
publishers.setEditable(false);
publishers.addItem("Any");
result = new JTextArea(4, 50);
result.setEditable(false);
priceChange = new JTextField(8);
priceChange.setText("-5.00");
try {
conn = getConnection();
Statement stat = conn.createStatement();
String query = "SELECT Name FROM Authors";
ResultSet rs = stat.executeQuery(query);
while (rs.next())
authors.addItem(rs.getString(1));
rs.close();
query = "SELECT Name FROM Publishers";
rs = stat.executeQuery(query);
while (rs.next())
publishers.addItem(rs.getString(1));
rs.close();
stat.close();
} catch (SQLException e) {
for (Throwable t : e)
result.append(t.getMessage());
} catch (IOException e) {
result.setText("" + e);
}
// we use the GBC convenience class of Core Java Volume 1 Chapter 9
add(authors, new GBC(0, 0, 2, 1));
add(publishers, new GBC(2, 0, 2, 1));
JButton queryButton = new JButton("Query");
queryButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
executeQuery();
}
});
add(queryButton, new GBC(0, 1, 1, 1).setInsets(3));
JButton changeButton = new JButton("Change prices");
changeButton.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent event) {
changePrices();
}
});
add(changeButton, new GBC(2, 1, 1, 1).setInsets(3));
add(priceChange, new GBC(3, 1, 1, 1).setFill(GBC.HORIZONTAL));
add(new JScrollPane(result), new GBC(0, 2, 4, 1).setFill(GBC.BOTH).setWeight(100, 100));
addWindowListener(new WindowAdapter() {
public void windowClosing(WindowEvent event) {
try {
if (conn != null)
conn.close();
} catch (SQLException e) {
for (Throwable t : e)
t.printStackTrace();
}
}
});
}
/**
* Executes the selected query.
*/
private void executeQuery() {
ResultSet rs = null;
try {
String author = (String) authors.getSelectedItem();
String publisher = (String) publishers.getSelectedItem();
if (!author.equals("Any") && !publisher.equals("Any")) {
if (authorPublisherQueryStmt == null)
authorPublisherQueryStmt = conn.prepareStatement(authorPublisherQuery);
authorPublisherQueryStmt.setString(1, author);
authorPublisherQueryStmt.setString(2, publisher);
rs = authorPublisherQueryStmt.executeQuery();
} else if (!author.equals("Any") && publisher.equals("Any")) {
if (authorQueryStmt == null)
authorQueryStmt = conn.prepareStatement(authorQuery);
authorQueryStmt.setString(1, author);
rs = authorQueryStmt.executeQuery();
} else if (author.equals("Any") && !publisher.equals("Any")) {
if (publisherQueryStmt == null)
publisherQueryStmt = conn.prepareStatement(publisherQuery);
publisherQueryStmt.setString(1, publisher);
rs = publisherQueryStmt.executeQuery();
} else {
if (allQueryStmt == null)
allQueryStmt = conn.prepareStatement(allQuery);
rs = allQueryStmt.executeQuery();
}
result.setText("");
while (rs.next()) {
result.append(rs.getString(1));
result.append(", ");
result.append(rs.getString(2));
result.append("\n");
}
rs.close();
} catch (SQLException e) {
for (Throwable t : e)
result.append(t.getMessage());
}
}
/**
* Executes an update statement to change prices.
*/
public void changePrices() {
String publisher = (String) publishers.getSelectedItem();
if (publisher.equals("Any")) {
result.setText("I am sorry, but I cannot do that.");
return;
}
try {
if (priceUpdateStmt == null)
priceUpdateStmt = conn.prepareStatement(priceUpdate);
priceUpdateStmt.setString(1, priceChange.getText());
priceUpdateStmt.setString(2, publisher);
int r = priceUpdateStmt.executeUpdate();
result.setText(r + " records updated.");
} catch (SQLException e) {
for (Throwable t : e)
result.append(t.getMessage());
}
}
/**
* Gets a connection from the properties specified in the file database.properties
* @return the database connection
*/
public static Connection getConnection() throws SQLException, IOException {
Properties props = new Properties();
FileInputStream in = new FileInputStream("database.properties");
props.load(in);
in.close();
String drivers = props.getProperty("jdbc.drivers");
if (drivers != null)
System.setProperty("jdbc.drivers", drivers);
String url = props.getProperty("jdbc.url");
String username = props.getProperty("jdbc.username");
String password = props.getProperty("jdbc.password");
return DriverManager.getConnection(url, username, password);
}
public static final int DEFAULT_WIDTH = 400;
public static final int DEFAULT_HEIGHT = 400;
private JComboBox authors;
private JComboBox publishers;
private JTextField priceChange;
private JTextArea result;
private Connection conn;
private PreparedStatement authorQueryStmt;
private PreparedStatement authorPublisherQueryStmt;
private PreparedStatement publisherQueryStmt;
private PreparedStatement allQueryStmt;
private PreparedStatement priceUpdateStmt;
private static final String authorPublisherQuery = "SELECT Books.Price, Books.Title FROM Books, BooksAuthors, Authors, Publishers"
+ " WHERE Authors.Author_Id = BooksAuthors.Author_Id AND BooksAuthors.ISBN = Books.ISBN"
+ " AND Books.Publisher_Id = Publishers.Publisher_Id AND Authors.Name = ?" + " AND Publishers.Name = ?";
private static final String authorQuery = "SELECT Books.Price, Books.Title FROM Books, BooksAuthors, Authors"
+ " WHERE Authors.Author_Id = BooksAuthors.Author_Id AND BooksAuthors.ISBN = Books.ISBN"
+ " AND Authors.Name = ?";
private static final String publisherQuery = "SELECT Books.Price, Books.Title FROM Books, Publishers"
+ " WHERE Books.Publisher_Id = Publishers.Publisher_Id AND Publishers.Name = ?";
private static final String allQuery = "SELECT Books.Price, Books.Title FROM Books";
private static final String priceUpdate = "UPDATE Books " + "SET Price = Price + ? "
+ " WHERE Books.Publisher_Id = (SELECT Publisher_Id FROM Publishers WHERE Name = ?)";
}
/*
This program is a part of the companion code for Core Java 8th ed.
(http://horstmann.com/corejava)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
/*
GBC - A convenience class to tame the GridBagLayout
Copyright (C) 2002 Cay S. Horstmann (http://horstmann.com)
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
import java.awt.*;
/**
This class simplifies the use of the GridBagConstraints
class.
*/
public class GBC extends GridBagConstraints {
/**
Constructs a GBC with a given gridx and gridy position and
all other grid bag constraint values set to the default.
@param gridx the gridx position
@param gridy the gridy position
*/
public GBC(int gridx, int gridy) {
this.gridx = gridx;
this.gridy = gridy;
}
/**
Constructs a GBC with given gridx, gridy, gridwidth, gridheight
and all other grid bag constraint values set to the default.
@param gridx the gridx position
@param gridy the gridy position
@param gridwidth the cell span in x-direction
@param gridheight the cell span in y-direction
*/
public GBC(int gridx, int gridy, int gridwidth, int gridheight) {
this.gridx = gridx;
this.gridy = gridy;
this.gridwidth = gridwidth;
this.gridheight = gridheight;
}
/**
Sets the anchor.
@param anchor the anchor value
@return this object for further modification
*/
public GBC setAnchor(int anchor) {
this.anchor = anchor;
return this;
}
/**
Sets the fill direction.
@param fill the fill direction
@return this object for further modification
*/
public GBC setFill(int fill) {
this.fill = fill;
return this;
}
/**
Sets the cell weights.
@param weightx the cell weight in x-direction
@param weighty the cell weight in y-direction
@return this object for further modification
*/
public GBC setWeight(double weightx, double weighty) {
this.weightx = weightx;
this.weighty = weighty;
return this;
}
/**
Sets the insets of this cell.
@param distance the spacing to use in all directions
@return this object for further modification
*/
public GBC setInsets(int distance) {
this.insets = new Insets(distance, distance, distance, distance);
return this;
}
/**
Sets the insets of this cell.
@param top the spacing to use on top
@param left the spacing to use to the left
@param bottom the spacing to use on the bottom
@param right the spacing to use to the right
@return this object for further modification
*/
public GBC setInsets(int top, int left, int bottom, int right) {
this.insets = new Insets(top, left, bottom, right);
return this;
}
/**
Sets the internal padding
@param ipadx the internal padding in x-direction
@param ipady the internal padding in y-direction
@return this object for further modification
*/
public GBC setIpad(int ipadx, int ipady) {
this.ipadx = ipadx;
this.ipady = ipady;
return this;
}
}
//File:database.properties
#jdbc.drivers=org.apache.derby.jdbc.ClientDriver jdbc.url=jdbc:derby://localhost:1527/COREJAVA;create=true
jdbc.username=dbuser jdbc.password=secret