How do I listen for bean’s property change event?

By I Wayan Saryada in Beans 1 Comment

In this example we’ll listen to bean’s property change event. We create a small bean named MyBean, adds attributes and getter/setter. We want to know or to get notified when the bean property name is changed.

First we need the add a PropertyChangeSupport field to the bean, with this object we will fire the property change event. When we need to listen for the change we have to create an implementation of a PropertyChangeListener. In this example we’ll just use the MyBean class as the listener.

The PropertyChangeListener has a method called propertyChange and inside this method we’ll implement the code to get the event fired by the PropertyChangeSupport.

package org.kodejava.bean;

import java.beans.PropertyChangeSupport;
import java.beans.PropertyChangeListener;
import java.beans.PropertyChangeEvent;
import java.io.Serializable;

public class MyBean implements PropertyChangeListener, Serializable {
    private Long id;
    private String name;

    private final PropertyChangeSupport pcs = new PropertyChangeSupport(this);

    public MyBean() {
        pcs.addPropertyChangeListener(this);
    }

    /**
     * This method gets called when a bound property is changed.
     *
     * @param evt A PropertyChangeEvent object describing the event source
     *            and the property that has changed.
     */
    public void propertyChange(PropertyChangeEvent evt) {
        System.out.println("Name      = " + evt.getPropertyName());
        System.out.println("Old Value = " + evt.getOldValue());
        System.out.println("New Value = " + evt.getNewValue());
    }

    public static void main(String[] args) {
        MyBean bean = new MyBean();
        bean.setName("My Initial Value");
        bean.setName("My New Value");
        bean.setName("My Yet Another Value");
    }


    //~ --------------------------------------------- Bean's Getters and Setters

    public Long getId() {
        return id;
    }

    public void setId(Long id) {
        this.id = id;
    }

    public String getName() {
        return name;
    }

    public void setName(String name) {
        String oldValue = this.name;
        this.name = name;

        // Fires a property change event
        pcs.firePropertyChange("name", oldValue, name);
    }
}

How do I sort strings using Collator class?

By I Wayan Saryada in Core API, Text Package 0 Comment

In this example we demonstrate how to use the java.text.Collator class to sort strings in language-specific order. Using the java.text.Collator class makes the string not just sorted by the ASCII code of their characters, but it will follow the language natural order of the characters.

package org.kodejava.text;

import java.util.List;
import java.util.ArrayList;
import java.util.Locale;
import java.text.Collator;

public class StringShortWithCollator {
    public static void main(String[] args) {
        List<String> fruits = new ArrayList<>();
        fruits.add("Guava");
        fruits.add("Banana");
        fruits.add("Orange");
        fruits.add("Mango");
        fruits.add("Apple");

        // Define a collator for US English.
        Collator collator = Collator.getInstance(Locale.US);

        // Sort the list base on the collator
        fruits.sort(collator);

        for (String fruit : fruits) {
            System.out.println("Fruit = " + fruit);
        }
    }
}

The result of the code snippet above are:

Fruit = Apple
Fruit = Banana
Fruit = Guava
Fruit = Mango
Fruit = Orange

How do I convert ResourceBundle to Properties?

By I Wayan Saryada in Core API, Util Package 0 Comment 
package org.kodejava.util;

import java.util.*;

public class ResourceBundleToProperties {
    public static void main(String[] args) {
        // Load resource bundle Messages_en_GB.properties from the classpath.
        ResourceBundle resource = ResourceBundle.getBundle("Messages", Locale.UK);

        // Call the convertResourceBundleToProperties method to convert the resource
        // bundle into a Properties object.
        Properties properties = convertResourceBundleToProperties(resource);

        // Print the entire contents of the Properties.
        Enumeration<Object> keys = properties.keys();
        while (keys.hasMoreElements()) {
            String key = (String) keys.nextElement();
            String value = (String) properties.get(key);
            System.out.println(key + " = " + value);
        }
    }

    /**
     * Convert ResourceBundle into a Properties object.
     *
     * @param resource a resource bundle to convert.
     * @return Properties a properties version of the resource bundle.
     */
    private static Properties convertResourceBundleToProperties(ResourceBundle resource) {
        Properties properties = new Properties();
        Enumeration<String> keys = resource.getKeys();
        while (keys.hasMoreElements()) {
            String key = keys.nextElement();
            properties.put(key, resource.getString(key));
        }
        return properties;
    }
}

How do I convert ResourceBundle to Map?

By I Wayan Saryada in Core API, Util Package 1 Comment

The following code snippet will convert a resource bundle into a map object, a key-value mapping. It will read from a file called Messages_en_GB.properties which corresponding to the Locale.UK. For example the file contain the following string. This file should be placed under the resources directory.

welcome.message = Hello World!

package org.kodejava.util;

import java.util.*;

public class ResourceBundleToMap {
    public static void main(String[] args) {
        // Load resource bundle Messages_en_GB.properties from the classpath.
        ResourceBundle resource = ResourceBundle.getBundle("Messages", Locale.UK);

        // Call the convertResourceBundleTopMap method to convert the resource
        // bundle into a Map object.
        Map<String, String> map = convertResourceBundleToMap(resource);

        // Print the entire contents of the Map.
        for (String key : map.keySet()) {
            String value = map.get(key);
            System.out.println(key + " = " + value);
        }
    }

    /**
     * Convert ResourceBundle into a Map object.
     *
     * @param resource a resource bundle to convert.
     * @return Map a map version of the resource bundle.
     */
    private static Map<String, String> convertResourceBundleToMap(ResourceBundle resource) {
        Map<String, String> map = new HashMap<>();
        Enumeration<String> keys = resource.getKeys();
        while (keys.hasMoreElements()) {
            String key = keys.nextElement();
            map.put(key, resource.getString(key));
        }
        return map;
    }
}

How do I decompress Java objects?

By I Wayan Saryada in Zip and GZIP 0 Comment

In the previous example How do I compress Java objects? we have manage to compress Java objects and stored them in file. In this example we will read the file and reconstruct the compressed objects. For the User class you can see in the previous example mentioned above.

package org.kodejava.util.zip;

import org.kodejava.util.support.User;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.ObjectInputStream;
import java.util.zip.GZIPInputStream;

public class UnzipObjectDemo {
    public static void main(String[] args) {
        File file = new File("user.dat");
        try (FileInputStream fis = new FileInputStream(file);
             GZIPInputStream gis = new GZIPInputStream(fis);
             ObjectInputStream ois = new ObjectInputStream(gis)) {

            User admin = (User) ois.readObject();
            User foo = (User) ois.readObject();

            System.out.println("Admin = [" + admin + "]");
            System.out.println("Foo = [" + foo + "]");
        } catch (IOException | ClassNotFoundException e) {
            e.printStackTrace();
        }
    }
}

Running the code snippet above will give us the following output:

Admin = [User{id=1, username='admin', password='secret', firstName='System', lastName='Administrator'}]
Foo = [User{id=2, username='foo', password='secret', firstName='Foo', lastName='Bar'}]