querydb.java

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/**
 * @version 1.20 1999-08-16
 * @author Cay Horstmann
 */

import java.net.*;
import java.sql.*;
import java.awt.*;
import java.awt.event.*;
import java.io.*;
import java.util.*;
import javax.swing.*;

public class QueryDB
{  public static void main(String[] args)
   {  JFrame frame = new QueryDBFrame();
      frame.show();
   }
}

class QueryDBFrame extends JFrame
   implements ActionListener
{  public QueryDBFrame()
   {  setTitle("QueryDB");
      setSize(400, 300);
      addWindowListener(new WindowAdapter()
         {  public void windowClosing(WindowEvent e)
            {  System.exit(0);
            }
         } );

      getContentPane().setLayout(new GridBagLayout());
      GridBagConstraints gbc = new GridBagConstraints();

      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
      {  con = getConnection();
         stmt = con.createStatement();

         String query = "SELECT Name FROM Authors";
         ResultSet rs = stmt.executeQuery(query);
         while (rs.next())
            authors.addItem(rs.getString(1));

         query = "SELECT Name FROM Publishers";
         rs = stmt.executeQuery(query);
         while (rs.next())
            publishers.addItem(rs.getString(1));
      }
      catch(Exception e)
      {  result.setText("Error " + e);
      }

      gbc.fill = GridBagConstraints.NONE;
      gbc.weightx = 100;
      gbc.weighty = 100;
      add(authors, gbc, 0, 0, 2, 1);

      add(publishers, gbc, 2, 0, 2, 1);

      gbc.fill = GridBagConstraints.NONE;
      JButton queryButton = new JButton("Query");
      queryButton.addActionListener(this);
      add(queryButton, gbc, 0, 1, 1, 1);

      JButton changeButton = new JButton("Change prices");
      changeButton.addActionListener(this);
      add(changeButton, gbc, 2, 1, 1, 1);

      gbc.fill = GridBagConstraints.HORIZONTAL;
      add(priceChange, gbc, 3, 1, 1, 1);

      gbc.fill = GridBagConstraints.BOTH;
      add(result, gbc, 0, 2, 4, 1);
   }

   public static Connection getConnection()
      throws SQLException, IOException
   {  Properties props = new Properties();
      String fileName = "QueryDB.properties";
      FileInputStream in = new FileInputStream(fileName);
      props.load(in);

      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);
   }

   private void add(Component c, GridBagConstraints gbc,
      int x, int y, int w, int h)
   {  gbc.gridx = x;
      gbc.gridy = y;
      gbc.gridwidth = w;
      gbc.gridheight = h;
      getContentPane().add(c, gbc);
   }

   public void actionPerformed(ActionEvent evt)
   {  String arg = evt.getActionCommand();
      if (arg.equals("Query"))
      {  ResultSet rs = null;
         try
         {  String author
               = (String)authors.getSelectedItem();
            String publisher
               = (String)publishers.getSelectedItem();
            if (!author.equals("Any")
               && !publisher.equals("Any"))
            {  if (authorPublisherQueryStmt == null)
               {  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 = ?";
                  authorPublisherQueryStmt
                  = con.prepareStatement(authorPublisherQuery);
               }
               authorPublisherQueryStmt.setString(1, author);
               authorPublisherQueryStmt.setString(2,
                  publisher);
               rs = authorPublisherQueryStmt.executeQuery();
            }
            else if (!author.equals("Any")
               && publisher.equals("Any"))
            {  if (authorQueryStmt == null)
               {  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 = ?";
                  authorQueryStmt
                     = con.prepareStatement(authorQuery);
               }
               authorQueryStmt.setString(1, author);
               rs = authorQueryStmt.executeQuery();
            }
            else if (author.equals("Any")
               && !publisher.equals("Any"))
            {  if (publisherQueryStmt == null)
               {  String publisherQuery =
"SELECT Books.Price, Books.Title " +
"FROM Books, Publishers " +
"WHERE Books.Publisher_Id = Publishers.Publisher_Id AND " +
"Publishers.Name = ?";
                  publisherQueryStmt
                     = con.prepareStatement(publisherQuery);
               }
               publisherQueryStmt.setString(1, publisher);
               rs = publisherQueryStmt.executeQuery();
            }
            else
            {  if (allQueryStmt == null)
               {  String allQuery =
"SELECT Books.Price, Books.Title FROM Books";
                  allQueryStmt
                     = con.prepareStatement(allQuery);
               }
               rs = allQueryStmt.executeQuery();
            }

            result.setText("");
            while (rs.next())
               result.append(rs.getString(1)
                  + " | " + rs.getString(2) + "\n");
            rs.close();
         }
         catch(Exception e)
         {  result.setText("Error " + e);
         }
      }
      else if (arg.equals("Change prices"))
      {  String publisher
            = (String)publishers.getSelectedItem();
         if (publisher.equals("Any"))
            result.setText
               ("I am sorry, but I cannot do that.");
         else
            try
            {  String updateStatement =
"UPDATE Books " +
"SET Price = Price + " + priceChange.getText() +
" WHERE Books.Publisher_Id = " +
"(SELECT Publisher_Id FROM Publishers WHERE Name = '" +
   publisher + "')";
               int r = stmt.executeUpdate(updateStatement);
               result.setText(r + " records updated.");
            }
            catch(Exception e)
            {  result.setText("Error " + e);
            }
      }
   }

   public void dispose()
   {  try
      {  stmt.close();
         con.close();
      }
      catch(SQLException e) {}
   }

   private JComboBox authors;
   private JComboBox publishers;
   private JTextField priceChange;
   private JTextArea result;
   private Connection con;
   private Statement stmt;
   private PreparedStatement authorQueryStmt;
   private PreparedStatement authorPublisherQueryStmt;
   private PreparedStatement publisherQueryStmt;
   private PreparedStatement allQueryStmt;
}