com.google.gwt.gears.sample.databasedemo.client.DatabaseDemo.java Source code

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Here is the source code for com.google.gwt.gears.sample.databasedemo.client.DatabaseDemo.java

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/*
 * Copyright 2008 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy of
 * the License at
 *
 * http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations under
 * the License.
 */
package com.google.gwt.gears.sample.databasedemo.client;

import com.google.gwt.core.client.EntryPoint;
import com.google.gwt.event.dom.client.ClickEvent;
import com.google.gwt.event.dom.client.ClickHandler;
import com.google.gwt.event.dom.client.KeyCodes;
import com.google.gwt.event.dom.client.KeyDownEvent;
import com.google.gwt.event.dom.client.KeyDownHandler;
import com.google.gwt.gears.client.Factory;
import com.google.gwt.gears.client.database.Database;
import com.google.gwt.gears.client.database.DatabaseException;
import com.google.gwt.gears.client.database.ResultSet;
import com.google.gwt.user.client.Window;
import com.google.gwt.user.client.ui.Button;
import com.google.gwt.user.client.ui.FlexTable;
import com.google.gwt.user.client.ui.HTML;
import com.google.gwt.user.client.ui.HorizontalPanel;
import com.google.gwt.user.client.ui.Label;
import com.google.gwt.user.client.ui.RootPanel;
import com.google.gwt.user.client.ui.TextBox;
import com.google.gwt.user.client.ui.VerticalPanel;

import java.util.Date;

/**
 * Sample application demonstrating how to use the {@link Database} class.
 */
public class DatabaseDemo implements EntryPoint {
    private static final int NUM_SAVED_ROWS = 3;
    private static final int NUM_DATA_TABLE_COLUMNS = 3;

    private final Button addButton = new Button("Add");
    private final Button clearButton = new Button("Clear Database");
    private Database db;
    private final TextBox input = new TextBox();
    private final FlexTable dataTable = new FlexTable();

    public void onModuleLoad() {
        VerticalPanel outerPanel = new VerticalPanel();
        outerPanel.setSpacing(10);
        outerPanel.getElement().getStyle().setPropertyPx("margin", 15);

        HorizontalPanel textAndButtonsPanel = new HorizontalPanel();
        textAndButtonsPanel.add(new Label("Enter a Phrase: "));
        textAndButtonsPanel.add(input);
        textAndButtonsPanel.add(addButton);
        textAndButtonsPanel.add(clearButton);
        outerPanel.add(textAndButtonsPanel);
        outerPanel.add(new Label("Last 3 Entries:"));
        outerPanel.add(dataTable);

        for (int i = 0; i <= NUM_SAVED_ROWS; ++i) {
            dataTable.insertRow(i);
            for (int j = 0; j < NUM_DATA_TABLE_COLUMNS; j++) {
                dataTable.addCell(i);
            }
        }
        dataTable.setWidget(0, 0, new HTML("<b>Id</b>"));
        dataTable.setWidget(0, 1, new HTML("<b>Phrase</b>"));
        dataTable.setWidget(0, 2, new HTML("<b>Timestamp</b>"));

        // Create the database if it doesn't exist.
        try {
            db = Factory.getInstance().createDatabase();
            db.open("database-demo");
            db.execute(
                    "CREATE TABLE IF NOT EXISTS Phrases (Id INTEGER PRIMARY KEY AUTOINCREMENT, Phrase VARCHAR(255), Timestamp INTEGER)");
        } catch (DatabaseException e) {
            RootPanel.get("demo").add(new HTML(
                    "Error opening or creating database: <font color=\"red\">" + e.toString() + "</font>"));
            // Fatal error. Do not build the interface.
            return;
        }

        input.addKeyDownHandler(new KeyDownHandler() {
            public void onKeyDown(KeyDownEvent event) {
                if (event.getNativeKeyCode() == KeyCodes.KEY_ENTER) {
                    insertPhrase();
                }
            }
        });

        addButton.addClickHandler(new ClickHandler() {
            public void onClick(ClickEvent event) {
                insertPhrase();
            }
        });

        clearButton.addClickHandler(new ClickHandler() {
            public void onClick(ClickEvent event) {
                clearPhrases();
                displayRecentPhrases();
            }
        });

        RootPanel.get("demo").add(outerPanel);
        displayRecentPhrases();
    }

    /**
     * Remove all phrases from the database.
     */
    private void clearPhrases() {
        try {
            db.execute("DELETE FROM Phrases");
        } catch (DatabaseException e) {
            Window.alert(e.toString());
        }
    }

    /**
     * Fill the labels with the phrases from the database.
     */
    private void displayRecentPhrases() {
        try {
            ResultSet rs = db.execute("SELECT * FROM Phrases ORDER BY Id DESC");
            int i;

            for (i = 1; rs.isValidRow(); ++i, rs.next()) {
                if (i <= NUM_SAVED_ROWS) {
                    dataTable.setText(i, 0, rs.getFieldAsString(0));
                    dataTable.setText(i, 1, rs.getFieldAsString(1));
                    dataTable.setText(i, 2, new Date(rs.getFieldAsLong(2)).toString());
                } else {
                    db.execute("DELETE FROM Phrases WHERE Id = ?", new String[] { rs.getFieldAsString(0) });
                }
            }
            // If a phrase has been removed, clear the label.
            for (; i <= NUM_SAVED_ROWS; i++) {
                for (int j = 0; j < NUM_DATA_TABLE_COLUMNS; j++) {
                    dataTable.clearCell(i, j);
                }
            }
            rs.close();
        } catch (DatabaseException e) {
            Window.alert(e.toString());
        }
    }

    /**
     * Add a new phrase to the database.
     */
    private void insertPhrase() {
        try {
            String phrase = input.getText();
            if (phrase.length() > 0) {
                db.execute("INSERT INTO Phrases (Phrase, Timestamp) VALUES (?, ?)",
                        new String[] { phrase, Long.toString(System.currentTimeMillis()) });
                displayRecentPhrases();
                input.setText("");
            }
        } catch (DatabaseException e) {
            Window.alert(e.toString());
        }
    }
}