How do I launch user-default mail client application?

By Wayan in AWT, Core API 0 Comment

Here is an example using the java.awt.Desktop class to open user’s default mail client application. There are two methods provided, the mail() and the mail(URI uri) methods.

When specifying the URI to the application will be opened with the message field filled with the mailto information. You can refer to the following document for the valid mailto URI scheme http://www.ietf.org/rfc/rfc2368.txt

package org.kodejava.awt;

import java.awt.*;
import java.io.IOException;
import java.net.URI;

public class RunningDefaultMailClient {
    public static void main(String[] args) {
        // Get an instance of Desktop. An UnsupportedOperationException will
        // be thrown if the platform doesn't support Desktop API.
        Desktop desktop = Desktop.getDesktop();

        try {
            // Open user-default mail client application.
            desktop.mail();
        } catch (IOException e) {
            e.printStackTrace();
        }

        try {
            // Open user-default mail client with the email message fields information.
            String message = "mailto:[email protected][email protected]&subject=First%20Email";
            URI uri = URI.create(message);
            desktop.mail(uri);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

How do I launch user-default web browser?

By Wayan in AWT, Core API 0 Comment

The code below show you how to browse a website using the user’s default web browser. To get the default web browser you can use the Desktop class browse(URI uri) method call.

package org.kodejava.awt;

import java.awt.Desktop;
import java.io.IOException;
import java.net.URI;

public class RunningDefaultBrowser {
    public static void main(String[] args) {
        URI uri = URI.create("https://kodejava.org");
        try {
            // Get Desktop instance of the current browser context. An 
            // UnsupportedOperationException will be thrown if the 
            // platform doesn't support Desktop API. 
            Desktop desktop = Desktop.getDesktop();

            // Browse the uri using user's default web browser.
            desktop.browse(uri);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

How do I get and display an image in Applet?

By Wayan in Applet, Core API 0 Comment

To display an image in an applet we first need to obtain the image object itself. A call to applet’s getImage(URL url, String name) method help us to create an image object from the specified URL of the image.

For displaying the image on the applet’s screen we draw it in the paint() method using Graphics.drawImage() method.

package org.kodejava.applet;

import java.applet.Applet;
import java.awt.*;

public class AppletGetImage extends Applet {
    private Image logo;

    @Override
    public void init() {
        // Get an Image object that can be painted on the Applet
        // screen. We need to supply the URL of the document as
        // the base location of the image and the location of the
        // image relative the base URL. 
        logo = getImage(getDocumentBase(), "/images/logo.png");
    }

    @Override
    public void paint(Graphics g) {
        g.drawRect(0, 0, getWidth() - 1, getHeight() - 1);
        g.drawImage(logo, 10, 10, this);
    }
}
** Deprecated: The Applet API is deprecated since JDK 9, no replacement.

How do I get Applet’s document URL?

By Wayan in Applet, Core API 0 Comment

The code snippet below show you how to get the URL of the document (HTML, JSP, etc.) where the Applet is embedded. To obtain this document URL we use the getDocumentBase() method call provided by the Applet class.

In the paint() method below we use the getDocumentBase() to create a URL as a link to an image to be displayed by our applet.

package org.kodejava.applet;

import java.applet.Applet;
import java.awt.*;

public class AppletDocumentBase extends Applet {
    private Image logo;

    @Override
    public void init() {
        // Locates logo image base on the URL of the document
        // where the Applet is embedded which is returned by
        // the getDocumentBase() method call.
        //
        // eg. http://localhost:8080/images/logo.jpg
        logo = getImage(getDocumentBase(), "/images/logo.png");
    }

    @Override
    public void paint(Graphics g) {
        g.setColor(Color.black);
        g.drawRect(0, 0, getWidth() - 1, getHeight() - 1);

        // Draw the logo image on the Applet surface.
        g.drawImage(logo, 10, 10, this);
    }
}
** Deprecated: The Applet API is deprecated since JDK 9, no replacement.

How do I set the maximum rows to read in a query?

By Wayan in JDBC 0 Comment

If you want to limit the result of your query, you can call the Statement.setMaxRows(int max) method. This call will allow the ResultSet object contains a maximum number of records specified in the parameter of the setMaxRows method.

Another way to limit the number of data returned in a query is to use the database-specific command such as the MySQL limit command.

package org.kodejava.jdbc;

import java.sql.*;

public class SetMaxRowExample {
    private static final String URL = "jdbc:mysql://localhost/kodejava";
    private static final String USERNAME = "kodejava";
    private static final String PASSWORD = "s3cr*t";

    public static void main(String[] args) {
        try (Connection connection =
                     DriverManager.getConnection(URL, USERNAME, PASSWORD)) {
            Statement statement = connection.createStatement();

            // Executes an SQL query to get the total number of data
            // in product table.
            String query = "select count(*) from product";
            ResultSet rs = statement.executeQuery(query);

            while (rs.next()) {
                System.out.println("Total Products: " + rs.getInt(1));
            }

            // Set the maximum row of data that can be stored in the
            // ResultSet.
            statement.setMaxRows(5);

            // Executes an SQL query to retrieve data from product
            // table.
            query = "select id, code, name, price from product";
            rs = statement.executeQuery(query);

            System.out.println("Data read after the MaxRows is set.");
            while (rs.next()) {
                System.out.println("ID: " + rs.getInt("id")
                                   + ", CODE: " + rs.getString("code")
                                   + ", NAME: " + rs.getString("name")
                                   + ", PRICE: " + rs.getBigDecimal("price"));
            }
        } catch (SQLException e) {
            e.printStackTrace();
        }
    }
}

When running the code, we’ll see that only 5 records were read from the product table instead of 10 records. This is the result of setting the maximum rows in the Statement object.

Below is the output of our code.

Total Products: 9
Data read after the MaxRows is set.
ID: 1, CODE: P0000001, NAME: UML Distilled 3rd Edition, PRICE: 25.00
ID: 3, CODE: P0000003, NAME: PHP Programming, PRICE: 20.00
ID: 4, CODE: P0000004, NAME: Longman Active Study Dictionary, PRICE: 40.00
ID: 5, CODE: P0000005, NAME: Ruby on Rails, PRICE: 24.00
ID: 6, CODE: P0000006, NAME: Championship Manager, PRICE: 0.00

Maven Dependencies

<dependency>
    <groupId>com.mysql</groupId>
    <artifactId>mysql-connector-j</artifactId>
    <version>8.4.0</version>
</dependency>

Maven Central