Facade pattern in Java : Facade Pattern « Design Pattern « Java

1. Java
2. Design Pattern
3. Facade Pattern

Facade pattern in Java

/*
The Design Patterns Java Companion

Copyright (C) 1998, by James W. Cooper

IBM Thomas J. Watson Research Center

*/


import java.awt.BorderLayout;
import java.awt.Button;
import java.awt.Color;
import java.awt.Component;
import java.awt.Dialog;
import java.awt.Frame;
import java.awt.Graphics;
import java.awt.GridLayout;
import java.awt.Label;
import java.awt.List;
import java.awt.Panel;
import java.awt.TextArea;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.ItemEvent;
import java.awt.event.ItemListener;
import java.sql.Connection;
import java.sql.DatabaseMetaData;
import java.sql.DriverManager;
import java.sql.ResultSet;
import java.sql.ResultSetMetaData;
import java.sql.Statement;
import java.util.Vector;

public class DatabaseFrame extends Frame implements ActionListener,
    ItemListener {
  Database db;

  List Tables, Columns, Data;

  TextArea query;

  Button Search, Quit;

  public DatabaseFrame() {
    super("Database demonstration");
    setGUI();

    db = new Database("sun.jdbc.odbc.JdbcOdbcDriver");
    db.Open("jdbc:odbc:Grocery prices", null);

    String tnames[] = db.getTableNames();
    loadList(Tables, tnames);

    String queryText = "SELECT * from yourTableName";

    query.setText(queryText);
  }

  //------------------------------------
  private void setGUI() {
    setBackground(Color.lightGray);
    setLayout(new BorderLayout());
    Panel pn = new Panel();
    add("North", pn);
    pn.setLayout(new GridLayout(1, 3));
    pn.add(new Label("Tables"));
    pn.add(new Label("Columns"));
    pn.add(new Label("Data"));
    Panel pc = new Panel();
    add("Center", pc);
    pc.setLayout(new GridLayout(1, 3));
    pc.add(Tables = new List(15));
    pc.add(Columns = new List(15));
    pc.add(Data = new List(15));
    Tables.addItemListener(this);
    Columns.addItemListener(this);

    Panel ps = new Panel();
    add("South", ps);
    ps.add(query = new TextArea("", 3, 40));
    addPanel(ps, Search = new Button("Run Query"));
    addPanel(ps, Quit = new Button("Quit"));
    Search.addActionListener(this);
    Quit.addActionListener(this);
    setBounds(100, 100, 500, 300);
    setVisible(true);
  }

  //------------------------------------
  private void addPanel(Panel ps, Component c) {
    Panel p = new Panel();
    ps.add(p);
    p.add(c);
  }

  //------------------------------------
  private void loadList(List list, String[] s) {
    list.removeAll();
    for (int i = 0; i < s.length; i++)
      list.add(s[i]);
  }

  //------------------------------------
  public void actionPerformed(ActionEvent e) {
    Object obj = e.getSource();
    if (obj == Quit)
      System.exit(0);
    if (obj == Search)
      clickedSearch();
  }

  //------------------------------------
  public void itemStateChanged(ItemEvent e) {
    Object obj = e.getSource();
    if (obj == Tables)
      showColumns();
    if (obj == Columns)
      showData();
  }

  //------------------------------------
  private void showColumns() {
    String cnames[] = db.getColumnNames(Tables.getSelectedItem());
    loadList(Columns, cnames);
  }

  //------------------------------------
  private void showData() {
    String colname = Columns.getSelectedItem();
    String colval = db.getColumnValue(Tables.getSelectedItem(), colname);
    Data.setVisible(false);
    Data.removeAll();
    Data.setVisible(true);

    colval = db.getNextValue(Columns.getSelectedItem());

    while (colval.length() > 0) {
      Data.add(colval);
      colval = db.getNextValue(Columns.getSelectedItem());
    }
  }

  //------------------------------------
  private void clickedSearch() {
    resultSet rs = db.Execute(query.getText());
    String cnames[] = rs.getMetaData();
    Columns.removeAll();
    queryDialog q = new queryDialog(this, rs);
    q.show();
  }

  //------------------------------------
  static public void main(String argv[]) {
    new DatabaseFrame();
  }
}

class queryDialog extends Dialog implements ActionListener {
  resultSet results;

  Button OK;

  textPanel pc;

  Vector tables;

  public queryDialog(Frame f, resultSet r) {
    super(f, "Query Result");
    results = r;
    setLayout(new BorderLayout());
    OK = new Button("OK");
    Panel p = new Panel();
    add("South", p);
    p.add(OK);
    OK.addActionListener(this);

    pc = new textPanel();
    pc.setBackground(Color.white);
    add("Center", pc);
    makeTables();
    setBounds(100, 100, 500, 300);
    setVisible(true);
    repaint();
  }

  //-------------------------------------
  private void makeTables() {
    tables = new Vector();
    String t[] = results.getMetaData();
    tables.addElement(t);
    while (results.hasMoreElements()) {
      tables.addElement(results.nextElement());
    }
  }

  //-------------------------------------
  public void actionPerformed(ActionEvent e) {
    setVisible(false);
  }

  //-------------------------------------
  class textPanel extends Panel {
    public void paint(Graphics g) {
      String s[];
      int x = 0;
      int y = g.getFontMetrics().getHeight();
      int deltaX = (int) 1.5f
          * (g.getFontMetrics().stringWidth("wwwwwwwwwwwwww"));
      for (int i = 0; i < tables.size(); i++) {
        s = (String[]) tables.elementAt(i);
        for (int j = 0; j < s.length; j++) {
          String st = s[j];
          g.drawString(st, x, y);
          x += deltaX;
        }
        x = 0;
        y += g.getFontMetrics().getHeight();
        if (i == 0)
          y += g.getFontMetrics().getHeight();
      }
    }

  }
}

class Database {
  Connection con;

  resultSet results;

  ResultSetMetaData rsmd;

  DatabaseMetaData dma;

  String catalog;

  String types[];

  String database_url;

  public Database(String driver) {
    types = new String[1];
    types[0] = "TABLES"; //initialize type array
    try {
      Class.forName(driver);
    } //load the Bridge driver
    catch (Exception e) {
      System.out.println(e.getMessage());
    }
  }

  //-----------------------------------
  public void close() {
    try {
      con.close();
    } catch (Exception e) {
      System.out.println("close error");
    }

  }

  //-----------------------------------

  public void Open(String url, String cat) {
    catalog = cat;
    database_url = url;
    try {
      con = DriverManager.getConnection(url);
      dma = con.getMetaData(); //get the meta data
    } catch (Exception e) {
      System.out.println(e.getMessage());
    }
  }

  //-----------------------------------
  public void reOpen() {
    try {
      con = DriverManager.getConnection(database_url);
      dma = con.getMetaData(); //get the meta data
    } catch (Exception e) {
      System.out.println(e.getMessage());
    }
  }

  //-----------------------------------
  public String[] getTableNames() {
    String[] tbnames = null;
    Vector tname = new Vector();
    //add the table names to a Vector
    //since we don't know how many there are
    try {
      results = new resultSet(dma.getTables(catalog, null, "%", types));
    } catch (Exception e) {
      System.out.println(e);
    }

    while (results.hasMoreElements())
      tname.addElement(results.getColumnValue("TABLE_NAME"));

    //copy the table names into a String array
    tbnames = new String[tname.size()];
    for (int i = 0; i < tname.size(); i++)
      tbnames[i] = (String) tname.elementAt(i);
    return tbnames;
  }

  //-----------------------------------
  public String[] getTableMetaData() {
    // return the table type information
    results = null;
    try {
      results = new resultSet(dma.getTables(catalog, null, "%", types));
    } catch (Exception e) {
      System.out.println(e.getMessage());
    }
    return results.getMetaData();
  }

  //-----------------------------------
  public String[] getColumnMetaData(String tablename) {
    //return the data on a column
    results = null;
    try {
      results = new resultSet(dma.getColumns(catalog, null, tablename,
          null));
    } catch (Exception e) {
      System.out.println(e.getMessage());
    }
    return results.getMetaData();
  }

  //-----------------------------------
  public String[] getColumnNames(String table) {
    //return an array of Column names
    String[] tbnames = null;
    Vector tname = new Vector();

    try {
      results = new resultSet(dma.getColumns(catalog, null, table, null));
      while (results.hasMoreElements())
        tname.addElement(results.getColumnValue("COLUMN_NAME"));
    } catch (Exception e) {
      System.out.println(e);
    }

    tbnames = new String[tname.size()];
    for (int i = 0; i < tname.size(); i++)
      tbnames[i] = (String) tname.elementAt(i);
    return tbnames;
  }

  //-----------------------------------
  public String getColumnValue(String table, String columnName) {
    //return the value of a given column
    String res = null;
    try {
      if (table.length() > 0)
        results = Execute("Select " + columnName + " from " + table
            + " order by " + columnName);
      if (results.hasMoreElements())
        res = results.getColumnValue(columnName);
    } catch (Exception e) {
      System.out.println("Column value error" + columnName
          + e.getMessage());
    }

    return res;
  }

  //-----------------------------------
  public String getNextValue(String columnName) {
    // return the next value in that column
    //using the remembered resultSet
    String res = "";
    try {
      if (results.hasMoreElements())
        res = results.getColumnValue(columnName);
    } catch (Exception e) {
      System.out
          .println("next value error" + columnName + e.getMessage());
    }

    return res;
  }

  //-----------------------------------
  public resultSet Execute(String sql) {
    //execute an SQL query on this database
    results = null;
    try {
      Statement stmt = con.createStatement();
      results = new resultSet(stmt.executeQuery(sql));
    } catch (Exception e) {
      System.out.println("execute error: " + e.getMessage());
    }
    return results;
  }
}

class resultSet {
  //this class is a higher level abstraction
  //of the JDBC ResultSet object
  ResultSet rs;

  ResultSetMetaData rsmd;

  int numCols;

  public resultSet(ResultSet rset) {
    rs = rset;
    try {
      //get the meta data and column count at once
      rsmd = rs.getMetaData();
      numCols = rsmd.getColumnCount();
    } catch (Exception e) {
      System.out.println("resultset error" + e.getMessage());
    }
  }

  //-----------------------------------
  public String[] getMetaData() {
    //returns an array of all the column names
    //or other meta data
    String md[] = new String[numCols];
    try {
      for (int i = 1; i <= numCols; i++)
        md[i - 1] = rsmd.getColumnName(i);
    } catch (Exception e) {
      System.out.println("meta data error" + e.getMessage());
    }
    return md;
  }

  //-----------------------------------
  public boolean hasMoreElements() {
    try {
      return rs.next();
    } catch (Exception e) {
      System.out.println("next error " + e.getMessage());
      return false;
    }
  }

  //-----------------------------------
  public String[] nextElement() {
    //copies contents of row into string array
    String[] row = new String[numCols];
    try {
      for (int i = 1; i <= numCols; i++)
        row[i - 1] = rs.getString(i);
    } catch (Exception e) {
      System.out.println("next element error" + e.getMessage());
    }
    return row;
  }

  //-------------------------------------
  public String getColumnValue(String columnName) {
    String res = "";
    try {
      res = rs.getString(columnName);
    } catch (Exception e) {
      System.out.println("Column value error:" + columnName
          + e.getMessage());
    }
    return res;
  }

  //-------------------------------------
  public String getColumnValue(int i) {
    String res = "";
    try {
      res = rs.getString(i);
    } catch (Exception e) {
      System.out.println("Column value error: " + i + " "
          + e.getMessage());
    }
    return res;
  }

  //----------------------------------------------
  public void finalize() {
    try {
      rs.close();
    } catch (Exception e) {
      System.out.println(e.getMessage());
    }
  }
}
           
       

Related examples in the same category

1.	Facade Pattern 2 in Java
2.	Facade Pattern