How do I create a single line JTextArea?

By Wayan in Swing 0 Comment

The following example will show you how to create a single line JTextArea. A single line means that you cannot insert a new line in the text area. When pressing the enter key it will be replaced by a space.

This can be done by putting a property called filterNewlines and set its value to Boolean.TRUE into the document model of the JTextArea.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;

public class SingleLineTextArea extends JFrame {
    private SingleLineTextArea() {
        initialize();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(
                () -> new SingleLineTextArea().setVisible(true));
    }

    private void initialize() {
        setSize(500, 200);
        setTitle("Single Line Text Area");
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());

        final JTextArea textArea = new JTextArea();
        textArea.setLineWrap(true);

        // Filter a new line, pressing enter key will be replaced
        // with a space instead.
        textArea.getDocument().putProperty("filterNewlines",
                Boolean.TRUE);

        JScrollPane scrollPane = new JScrollPane(textArea);

        // Pressing the Save button print out the text area text
        // into the console.
        JButton button = new JButton("Save");
        button.addActionListener(e -> System.out.println(textArea.getText()));
        getContentPane().add(scrollPane, BorderLayout.CENTER);
        getContentPane().add(button, BorderLayout.SOUTH);
    }
}

The screenshot of the result of the code snippet above is:

Single Line JTextArea Demo

How do I move focus from JTextArea using TAB key?

By Wayan in Swing 6 Comments

The default behavior when pressing the tabular key in a JTextArea is to insert a tab spaces in the text area. In this example you’ll see how to change this to make the tab key to transfer focus to other component forward or backward.

The main routine can be found in the key listener section. When the tab key is pressed we will tell the text area to transfer to focus into other component. Let’s see the code snippet below.

package org.kodejava.swing;

import javax.swing.JFrame;
import javax.swing.JPasswordField;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.JTextField;
import javax.swing.SwingUtilities;
import javax.swing.WindowConstants;
import java.awt.BorderLayout;
import java.awt.event.KeyAdapter;
import java.awt.event.KeyEvent;

public class TextAreaTabMoveFocus extends JFrame {
    public TextAreaTabMoveFocus() {
        initialize();
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(
                () -> new TextAreaTabMoveFocus().setVisible(true));
    }

    private void initialize() {
        setSize(500, 200);
        setTitle("JTextArea TAB DEMO");
        setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        setLayout(new BorderLayout());

        JTextField textField = new JTextField();
        JPasswordField passwordField = new JPasswordField();
        final JTextArea textArea = new JTextArea();
        JScrollPane scrollPane = new JScrollPane(textArea);

        // Add key listener to change the TAB behavior in
        // JTextArea to transfer focus to other component forward
        // or backward.
        textArea.addKeyListener(new KeyAdapter() {
            @Override
            public void keyPressed(KeyEvent e) {
                if (e.getKeyCode() == KeyEvent.VK_TAB) {
                    if (e.getModifiersEx() > 0) {
                        textArea.transferFocusBackward();
                    } else {
                        textArea.transferFocus();
                    }
                    e.consume();
                }
            }
        });

        getContentPane().add(textField, BorderLayout.NORTH);
        getContentPane().add(scrollPane, BorderLayout.CENTER);
        getContentPane().add(passwordField, BorderLayout.SOUTH);
    }
}

The output of the code snippet above is:

JTextArea Move Focus Using Tab

How do I initialize and destroy beans in Spring?

By Wayan in Spring Core 1 Comment

When creating an instance of a bean you might need to do some initialization to the bean. Likewise, when the bean is no longer needed and removed from the Spring container you might want to do some cleanup routine or destroy the bean.

To do this initialization and destroy routine you can use the init-method and destroy-method attribute when declaring a bean in spring configuration using the <bean> element.

By defining the init-method and destroy-method it will allow the Spring Container to call the initialization method right after the bean created. And just before the bean removed and discarded from the container, the defined destroy method will be called. Let’s see some code snippet as an example.

package org.kodejava.spring.core;

public class AutoEngine {
    public void initialize() {
        System.out.println("AutoEngine.initialize");
    }

    public void destroy() {
        System.out.println("AutoEngine.destroy");
    }
}

Below is the Spring configuration file that where we register the bean. You’ll see in the configuration there are additional attributes that we add to the bean.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="engine" class="org.kodejava.spring.core.AutoEngine" init-method="initialize" destroy-method="destroy" />

</beans>

Create a small program to execute our demo:

package org.kodejava.spring.core;

import org.springframework.context.ConfigurableApplicationContext;
import org.springframework.context.support.ClassPathXmlApplicationContext;

public class InitDestroyDemo {
    public static void main(String[] args) {
        ConfigurableApplicationContext context =
                new ClassPathXmlApplicationContext("init-destroy.xml");

        AutoEngine engine = (AutoEngine) context.getBean("engine");

        // context.close will remove the bean from the container. 
        // This will call our bean destroy method.
        context.close();
    }
}

When you run the program it will print the following output:

AutoEngine.initialize
AutoEngine.destroy

The advantage of using this method to initialize or clean up the bean is that it does not mandate our bean to implement or extend any Spring API which will make our bean reusable on other container beside Spring.

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>5.3.23</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-beans</artifactId>
        <version>5.3.23</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context-support</artifactId>
        <version>5.3.23</version>
    </dependency>
</dependencies>

Maven Central Maven Central Maven Central

How do I read text file into JTextArea?

By Wayan in Swing 0 Comment

Using the read(Reader in, Object desc) method inherited from the JTextComponent allow us to populate a JTextArea with text content from a file. This example will show you how to do it.

In this example we use an InputStreamReader to read a file from our application resource. You could use other Reader implementation such as the FileReader to read the content of a file. Let’s see the code below.

package org.kodejava.swing;

import javax.swing.*;
import java.awt.*;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.Objects;

public class PopulateTextAreaFromFile extends JPanel {
    public PopulateTextAreaFromFile() {
        initialize();
    }

    public static void showFrame() {
        JPanel panel = new PopulateTextAreaFromFile();
        panel.setOpaque(true);

        JFrame frame = new JFrame("Populate JTextArea from File");
        frame.setDefaultCloseOperation(WindowConstants.EXIT_ON_CLOSE);
        frame.setContentPane(panel);
        frame.pack();
        frame.setVisible(true);
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(PopulateTextAreaFromFile::showFrame);
    }

    private void initialize() {
        JTextArea textArea = new JTextArea();
        JScrollPane scrollPane = new JScrollPane(textArea);
        try {
            // Read some text from the resource file to display in
            // the JTextArea.
            textArea.read(new InputStreamReader(Objects.requireNonNull(
                    getClass().getResourceAsStream("/data.txt"))), null);
        } catch (IOException e) {
            e.printStackTrace();
        }

        this.setPreferredSize(new Dimension(500, 200));
        this.setLayout(new BorderLayout());
        this.add(scrollPane, BorderLayout.CENTER);
    }
}

The output of the code snippet above is:

Read Text File into JTextArea

How do I define bean scoping in Spring?

By Wayan in Spring Core 0 Comment

Bean scoping is how the bean is created and returned from the spring container to the bean requester. By default, the scope of all bean is singleton. The spring container will always return the same bean whenever this bean is required, for instance when in injected or call using the getBean() method from the application context.

There are five types of bean scope define in the Spring Container:

Scope Description
singleton Scope the bean definition to a single bean instance per Spring Container. This is the default scope when no scope is defined when creating a bean.
prototype Scope the bean to allow multiple times bean creation. This will create a new bean for each time the bean is required.
request Scope the bean definition to a single HTTP request. *
session Scope the bean definition to a single HTTP session. *
global-session Scope the bean definition to a global HTTP session. *

*) This is only valid when using the web-capable Spring context.

Let’s see the difference between Singleton and Prototype scope. First we’ll create our DummyService class.

package org.kodejava.spring.core;

public class DummyService {
    private String message;

    public String getMessage() {
        return message;
    }

    public void setMessage(String message) {
        this.message = message;
    }
}

Singleton Scope

By default, when no scope defined it will be a singleton.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="service" class="org.kodejava.spring.core.DummyService" />

</beans>

Now create a program to run our example. First will run it using the singleton.xml as the configuration.

package org.kodejava.spring.core;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class BeanScopeDemo {
    public static void main(String[] args) {
        try (var context = new ClassPathXmlApplicationContext("singleton.xml")) {
            DummyService serviceA = (DummyService) context.getBean("service");
            serviceA.setMessage("Hello From A");
            System.out.println("Message A = " + serviceA.getMessage());

            DummyService serviceB = (DummyService) context.getBean("service");
            System.out.println("Message B = " + serviceB.getMessage());
        }
    }
}

The output of the singleton configuration is:

Message A = Hello From A
Message B = Hello From A

The above output show that the message printed by the serviceB is the same as the serviceA. We don’t even set the message in the serviceB explicitly. It prints the same message because the getBean() method actually return the same bean both for serviceA and serviceB. This is the singleton scope.

Prototype Scope

To change the scope to prototype use the scope attribute in the bean element as shown below.

<?xml version="1.0" encoding="UTF-8"?>
<beans xmlns="http://www.springframework.org/schema/beans" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd">

    <bean id="service" class="org.kodejava.spring.core.DummyService" scope="prototype" />

</beans>

package org.kodejava.spring.core;

import org.springframework.context.support.ClassPathXmlApplicationContext;

public class BeanScopePrototypeDemo {
    public static void main(String[] args) {
        try (var context = new ClassPathXmlApplicationContext("prototype.xml")) {
            DummyService serviceA = (DummyService) context.getBean("service");
            serviceA.setMessage("Hello From A");
            System.out.println("Message A = " + serviceA.getMessage());

            DummyService serviceB = (DummyService) context.getBean("service");
            System.out.println("Message B = " + serviceB.getMessage());
        }
    }
}

Now if you try to run the same program again but changing the configuration to prototype.xml you’ll get the following output printed:

Message A = Hello From A
Message B = null

The serviceB now print a different message. This is the effect of using the prototype scope. When we call the getBean() a new bean will be created per request.

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-core</artifactId>
        <version>5.3.23</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-beans</artifactId>
        <version>5.3.23</version>
    </dependency>
    <dependency>
        <groupId>org.springframework</groupId>
        <artifactId>spring-context-support</artifactId>
        <version>5.3.23</version>
    </dependency>
</dependencies>

Maven Central Maven Central Maven Central