How do I use ReflectionToStringBuilder class?

By Wayan in Apache Commons, Commons Lang 0 Comment

Implementing toString() method sometimes can become a time-consuming process. If you have a class with a few fields, it might be alright. However, when you deal with a lot of fields, it will surely take some time to update this method every time a new field comes and goes.

Here comes the ReflectionToStringBuilder class that can help you to automate the process of implementing the toString() method. This class provides a static toString() method that takes at least a single parameter that refer to an object instance from where the string will be generated.

We can also format the result of the generated string. In the example below we create the to string method with a ToStringStyle.MULTI_LINE_STYLE and we can also output transients and static fields if we want, which by default omitted.

package org.kodejava.commons.lang;

import org.apache.commons.lang3.builder.ReflectionToStringBuilder;
import org.apache.commons.lang3.builder.ToStringStyle;

public class ReflectionToStringDemo {
    public static final String KEY = "APP-KEY";

    private Integer id;
    private String name;
    private String description;
    private transient String secretKey;

    public ReflectionToStringDemo(Integer id, String name, String description,
                                  String secretKey) {
        this.id = id;
        this.name = name;
        this.description = description;
        this.secretKey = secretKey;
    }

    public static void main(String[] args) {
        ReflectionToStringDemo demo = new ReflectionToStringDemo(1, "MANUTD",
                "Manchester United", "secret**");
        System.out.println("Demo = " + demo);
    }

    @Override
    public String toString() {
        // Generate toString including transient and static fields.
        return ReflectionToStringBuilder.toString(this,
                ToStringStyle.MULTI_LINE_STYLE, true, true);
    }
}

The output produced by the code snippet above is:

Demo = org.kodejava.example.commons.lang.ReflectionToStringDemo@452b3a41[
  id=1
  name=MANUTD
  description=Manchester United
  KEY=APP-KEY
  secretKey=secret**
]

Maven Dependencies

<dependency>
    <groupId>org.apache.commons</groupId>
    <artifactId>commons-lang3</artifactId>
    <version>3.14.0</version>
</dependency>

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How do I read system property as an integer?

By Wayan in Core API, Lang Package 0 Comment

The Integer.getInteger() methods allows us to easily read system property and convert it directly to Integer object. This method call the System.getProperty() method and then convert it to integer by calling the Integer.decode() method.

package org.kodejava.lang;

public class IntegerProperty {
    public static void main(String[] args) {
        // Add properties to the system. In this example we create a
        // dummy major and minor version for our application.
        System.setProperty("app.major.version", "2021");
        System.setProperty("app.minor.version", "9");

        // In the code below we use the Integer.getInteger() method to
        // read our application version from the value specified in the
        // system properties.
        Integer major = Integer.getInteger("app.major.version");
        Integer minor = Integer.getInteger("app.minor.version");
        System.out.println("App version = " + major + "." + minor);
    }
}

The output of the code snippet:

App version = 2021.9

How do I decode string to integer?

By Wayan in Core API, Lang Package 0 Comment

The static Integer.decode() method can be used to convert a string representation of a number into an Integer object. Under the cover this method call the Integer.valueOf(String s, int radix).

The string can start with the optional negative sign followed with radix specified such as 0x, 0X, # for hexadecimal value, 0 (zero) for octal number.

package org.kodejava.lang;

public class IntegerDecode {
    public static void main(String[] args) {
        String decimal = "10"; // Decimal
        String hex = "0XFF"; // Hex
        String octal = "077"; // Octal

        Integer number = Integer.decode(decimal);
        System.out.println("String [" + decimal + "] = " + number);

        number = Integer.decode(hex);
        System.out.println("String [" + hex + "] = " + number);

        number = Integer.decode(octal);
        System.out.println("String [" + octal + "] = " + number);
    }
}

The result of the code snippet above:

String [10] = 10
String [0XFF] = 255
String [077] = 63

How do I get MAC address of a host?

By Wayan in Core API, Networking 4 Comments

Previously for obtaining a MAC address we need to use a native code as a solution. In JDK 1.6 a new method is added in the java.net.NetworkInterface class, this method is getHardwareAddress().

package org.kodejava.net;

import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.net.UnknownHostException;

public class MacAddress {
    public static void main(String[] args) {
        try {
            // InetAddress address = InetAddress.getLocalHost();
            InetAddress address = InetAddress.getByName("192.168.0.105");

            /*
             * Get NetworkInterface for the current host and then read
             * the hardware address.
             */
            NetworkInterface ni = NetworkInterface.getByInetAddress(address);
            if (ni != null) {
                byte[] mac = ni.getHardwareAddress();
                if (mac != null) {
                    /*
                     * Extract each array of mac address and convert it
                     * to hexadecimal with the following format
                     * 08-00-27-DC-4A-9E.
                     */
                    for (int i = 0; i < mac.length; i++) {
                        System.out.format("%02X%s", mac[i], (i < mac.length - 1) ? "-" : "");
                    }
                } else {
                    System.out.println("Address doesn't exist or is not accessible.");
                }
            } else {
                System.out.println("Network Interface for the specified address is not found.");
            }
        } catch (UnknownHostException | SocketException e) {
            e.printStackTrace();
        }
    }
}

How do I retrieve a list of Hibernate’s persistent objects?

By Wayan in Hibernate 0 Comment

In this example we add the function to read a list of records in our LabelService class. This function will read all Label persistent object from database. You can see the other functions such as saveLabel, getLabel and deleteLabel in the related example section of this example.

package org.kodejava.hibernate.service;

import org.hibernate.Session;
import org.kodejava.hibernate.SessionFactoryHelper;
import org.kodejava.hibernate.model.Label;

import java.util.List;

public class LabelService {
    public List<Label> getLabels() {
        Session session =
                SessionFactoryHelper.getSessionFactory().getCurrentSession();
        session.beginTransaction();

        // We read labels record from database using a simple Hibernate
        // query, Hibernate Query Language (HQL).
        List<Label> labels = session.createQuery("from Label", Label.class)
                .list();
        session.getTransaction().commit();

        return labels;
    }

    public void saveLabel(Label label) {
        // To save an object we first get a session by calling 
        // getCurrentSession() method from the SessionFactoryHelper class. 
        // Next we create a new transaction, save the Label object and 
        // commit it to database,
        Session session = SessionFactoryHelper.getSessionFactory()
                .getCurrentSession();

        session.beginTransaction();
        session.save(label);
        session.getTransaction().commit();
    }
}

package org.kodejava.hibernate;

import org.kodejava.hibernate.model.Label;
import org.kodejava.hibernate.service.LabelService;

import java.util.Date;
import java.util.List;

public class ListDemo {
    public static void main(String[] args) {
        LabelService service = new LabelService();

        // Creates a Label object we are going to store in the database.
        // We set the name, modified by and modified date information.
        Label newLabel = new Label();
        newLabel.setName("PolyGram");
        newLabel.setCreated(new Date());

        // Call the LabelManager saveLabel method.
        service.saveLabel(newLabel);

        List<Label> labels = service.getLabels();
        for (Label label : labels) {
            System.out.println("Label = " + label);
        }
    }
}

Maven Dependencies

<dependencies>
    <dependency>
        <groupId>org.hibernate</groupId>
        <artifactId>hibernate-core</artifactId>
        <version>5.6.9.Final</version>
    </dependency>
    <dependency>
        <groupId>com.mysql</groupId>
        <artifactId>mysql-connector-j</artifactId>
        <version>8.0.33</version>
    </dependency>
</dependencies>

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