Chip 1998 July/Chip_1998-07_cd.bin/zkuste/JBuilder/BDK/Win/bdk_sep97.exe/_SETUP.1/Select.java

Java Source | 1997-09-10 | 6.3 KB | 291 lines

package sunw.demo.select;

/**
 * This class is a simple demo database viewer.
 * Given a URL it will go talk to a database and fill all its tables.
 * The user can then chose a table and the tool can either display metadata
 * informtion about the table or display all its rows.
 *
 * @author kgh
 */

import java.sql.*;
import java.awt.*;
import java.util.*;

public class Select extends Panel {

    public Select() {
    setLayout(null);
    setSize(200, 300);

    initialize();
    }

    private void initialize() {
    if (text != null) {
        return;
    }
    removeAll();

        text = new java.awt.List();
        text.setFont(new Font("Courier", Font.PLAIN, 12));
    add(text);

        status = new Label("", Label.LEFT);
    add(status);

    doLayout();

    new WorkerThread(this);
    }

    // This is called from the worker thread.  This is where we actually
    // do any real work, like talking to the database.
    // Note that we have to be careful about concurrency control here so
    // thav we don't wedge the GU while we're off chatting to the database.

    void doWork() {
    for (;;) {
        int work = getWork();
        if (work == DO_SELECT) {
        select();
        }
        }
    }

    synchronized int getWork() {
    work = NO_WORK;
    while (work == NO_WORK) {
        try {
        wait();
        } catch (Exception ex) {
        }
    }
    int result = work;
    return (result);
    }

    void select() {
    // System.err.println("Doing select with: " + selectString);

    text.removeAll();

    Connection con = Util.connect(url, user, password, status);
    try {
        Statement s = con.createStatement();
        ResultSet rs = s.executeQuery(selectString);

        ResultSetMetaData md = rs.getMetaData();
        int columns = md.getColumnCount();
        int widths[] = new int[columns+1];
        Vector contents[] = new Vector[columns+1];
        for (int col = 1; col <= columns; col++) {
        widths[col] = md.getColumnName(col).length();
        contents[col] = new Vector();
        }

        int rows = 0;
        while (rs.next() && rows < maxRows) {
        for (int col = 1; col <= columns; col++) {
            String field = rs.getString(col);
            if (field == null) {
            field = "";
            }
            if (field.length() > 80) {
            field = field.substring(0,80);
            }
            if (field.length() > widths[col]) {
            widths[col] = field.length();
            }
            contents[col].addElement(field);
        }
        rows++;
        }

        // Create the header string.
        String header = "";
        for (int col = 1; col <= columns; col++) {
            String field = md.getColumnName(col);
        int pad = widths[col] - field.length();
        if (col != 1) {
            pad++;
        }
        if (pad > 0) {
            header += spaces.substring(0, pad);
        }
        header += field;
        }
        text.addItem(header);

        // Add the indivbidual database rows
        for (int row = 0; row < rows; row++) {
        String line = "";
            for (int col = 1; col <= columns; col++) {
            String field = (String)contents[col].elementAt(row);
            int pad = widths[col] - field.length();
            if (col != 1) {
            pad++;
            }
            if (pad > 0) {
            line += spaces.substring(0, pad);
            }
            line += field;
        }
               text.addItem(line);
        }

        if (text.getItemCount() >= maxRows) {
            status.setText("Only read first " + maxRows + " rows");
        } else {
              status.setText("Done.");
        }

    } catch (SQLException sx)  {
        System.err.println("Caught " + sx);
        status.setText("Caught " + sx);
    }

    Util.disconnect(con);

    doLayout();

    }

    public synchronized void doLayout() {
    initialize();
    int width = getSize().width;
    int height = getSize().height;
    text.setBounds(0, 0, width, height-40);
    status.setBounds(15, height-30, 2*width, 25);
    }

    /**
     * @deprecated provided for backward compatibility with old layout managers.
     */

    public void layout() {
    doLayout();
    }

    //------------------------------------------------------------
    // property accessors.

    public String getURL() {
    return url;
    }

    public void setURL(String url) {
    this.url = url;
    }

    public String getUser() {
    return user;
    }

    public void setUser(String user) {
    this.user = user;
    }

    public String getPassword() {
    return password;
    }

    public void setPassword(String password) {
    this.password = password;
    }

    public String getSQL() {
    return selectString;
    }

    public void setSQL(String sql) {
    selectString = sql;
    }

    public int getMaxRows() {
    return maxRows;
    }

    public void setMaxRows(int maxRows) {
    this.maxRows = maxRows;
    }


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

    // Serialization support.

    private void writeObject(java.io.ObjectOutputStream s)
                      throws java.io.IOException
    {
    // Clear the current display so we don't write all
    // the current field values.
    text.removeAll();
        s.defaultWriteObject();
    }

    private void readObject(java.io.ObjectInputStream s)
          throws java.lang.ClassNotFoundException,
             java.io.IOException
    {
        s.defaultReadObject();
    initialize();
    }

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

    // Event handler to re-read database state:
    public void update(java.awt.event.ActionEvent evt) {
    update();
    }

    // Public method to re-read database state.
    public synchronized void update() {
    work = DO_SELECT;
    notify();
    }

    //------------------------------------------------------------
    // GUI state:

    private transient Label status;
    private transient java.awt.List text;

    // Keep track of pending work for the worker thread:
    private final static int NO_WORK = 0;
    private final static int DO_SELECT = 3;
    private transient int work = NO_WORK;

    private final static String spaces =
        "                                           " +
        "                                           " +
        "                                           ";

    //------------------------------------------------------------
    // Database related state:
    private String url = "jdbc:odbc:SQLSERVER";
    private String user = "guest";
    private String password = "guest";
    private String selectString = "";
    private int maxRows = 200;
}


// The worker thread just calls into the given Select()

class WorkerThread extends Thread {
    WorkerThread(Select tvarg) {
        tv = tvarg;
        this.start();
    }

    public void run() {
    tv.doWork();
    }

    private Select tv;
}