Other Libraries - Learn Java by Examples

How do I convert object into JSON?

By I Wayan Saryada in Google Gson Last modified: May 31, 2024 0 Comment

In this example we are using Google Gson to convert an object (Student object) into JSON notation. Practically we can use this library to convert any object in Java, and it is quite simple. You just need to create an instance of Gson class and then call the toJson() method and pass the object to be converted into JSON string.

package org.kodejava.gson;

import com.google.gson.Gson;
import org.kodejava.gson.support.Student;

import java.util.Calendar;

public class StudentToJson {
    public static void main(String[] args) {
        Calendar dob = Calendar.getInstance();
        dob.set(2000, Calendar.FEBRUARY, 1, 0, 0, 0);
        Student student = new Student("Duke", "Menlo Park", dob.getTime());

        Gson gson = new Gson();
        String json = gson.toJson(student);
        System.out.println("json = " + json);
    }
}

When you run the example above you’ll get an output like:

json = {"name":"Duke","address":"Menlo Park","dateOfBirth":"Feb 1, 2000 12:00:00 AM"}

Below is our Student class.

package org.kodejava.gson.support;

import java.io.Serializable;
import java.util.Date;

public class Student implements Serializable {
    private String name;
    private String address;
    private Date dateOfBirth;

    public Student() {
    }

    public Student(String name, String address, Date dateOfBirth) {
        this.name = name;
        this.address = address;
        this.dateOfBirth = dateOfBirth;
    }

    public String getName() {
        return name;
    }

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

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public Date getDateOfBirth() {
        return dateOfBirth;
    }

    public void setDateOfBirth(Date dateOfBirth) {
        this.dateOfBirth = dateOfBirth;
    }
}

Maven Dependencies

<dependency>
    <groupId>com.google.code.gson</groupId>
    <artifactId>gson</artifactId>
    <version>2.11.0</version>
</dependency>

How do I convert JDOM Document to String?

By I Wayan Saryada in JDOM Last modified: June 3, 2024 0 Comment

This example demonstrate how to convert JDOM Document object to a String using the XMLOutputter.outputString(Document doc) method.

package org.kodejava.jdom;

import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.output.Format;
import org.jdom2.output.XMLOutputter;

public class JDOMDocumentToString {
    public static void main(String[] args) {
        Document document = new Document();
        Element root = new Element("rows");

        // Creating a child for the root element. Here we can see how to
        // set the text of an xml element.
        Element child = new Element("row");
        child.addContent(new Element("firstname").setText("Alice"));
        child.addContent(new Element("lastname").setText("Mallory"));
        child.addContent(new Element("address").setText("Sunset Road"));

        // Add the child to the root element and add the root element as
        // the document content.
        root.addContent(child);
        document.setContent(root);

        // Create an XMLOutputter object with pretty formatter. Calling
        // the outputString(Document doc) method convert the document
        // into string data.
        XMLOutputter outputter = new XMLOutputter(Format.getPrettyFormat());
        String xmlString = outputter.outputString(document);
        System.out.println(xmlString);
    }
}

The result of our code snippet:

<?xml version="1.0" encoding="UTF-8"?>
<rows>
  <row>
    <firstname>Alice</firstname>
    <lastname>Mallory</lastname>
    <address>Sunset Road</address>
  </row>
</rows>

Maven Dependencies

<dependency>
    <groupId>org.jdom</groupId>
    <artifactId>jdom2</artifactId>
    <version>2.0.6.1</version>
</dependency>

How do I generate a random alphanumeric string?

The code below show you how to use the Apache Commons-Lang RandomStringUtils class to generate some random string data.

package org.kodejava.commons.lang;

import org.apache.commons.lang3.RandomStringUtils;

public class RandomStringUtilsDemo {
    public static void main(String[] args) {
        // Creates a 64-chars length random string of number.
        String result = RandomStringUtils.random(64, false, true);
        System.out.println("random = " + result);

        // Creates a 64-chars length of random alphabetic string.
        result = RandomStringUtils.randomAlphabetic(64);
        System.out.println("random = " + result);

        // Creates a 32-chars length of random ascii string.
        result = RandomStringUtils.randomAscii(32);
        System.out.println("random = " + result);

        // Creates a 32-chars length of string from the defined array of
        // characters including numeric and alphabetic characters.
        result = RandomStringUtils.random(32, 0, 20, true, true,
                "qw32rfHIJk9iQ8Ud7h0X".toCharArray());
        System.out.println("random = " + result);
    }
}

The example of our program result are:

random = 6251115933802303614285104650603664973302700879175809706257640062
random = EbKuzxERdBtCCHtbRuYnLwfnirtIqkcwwHxvZofkaGLNsNblCaVoLXFxfjYjXSHk
random = v9cJK?=d-Jl b-pisn9vUGxCV1&*>StY
random = XirkhUHHfwUf3kih8Hw877882d9i8Q3q

Maven Dependencies

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

How do I read a file into byte array using Apache Commons IO?

By I Wayan Saryada in Apache Commons, Commons IO Last modified: June 4, 2024 0 Comment

The following example shows you how to read file contents into byte array. We use the IOUtils class of the Apache Commons IO library.

package org.kodejava.commons.io;

import org.apache.commons.io.IOUtils;

import java.io.File;
import java.io.FileInputStream;
import java.io.IOException;
import java.io.InputStream;

public class FileToByteArray {
    public static void main(String[] args) {
        File file = new File("README.md");
        try {
            InputStream is = new FileInputStream(file);
            byte[] bytes = IOUtils.toByteArray(is);

            System.out.println("Byte array size: " + bytes.length);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.16.1</version>
</dependency>

How do I get the content of an InputStream as a String?

By I Wayan Saryada in Apache Commons, Commons IO Last modified: June 4, 2024 0 Comment

We can use the code below to convert the content of an InputStream into a String. At first, we use FileInputStream create to a stream to a file that going to be read. IOUtils.toString(InputStream input, String encoding) method gets the content of the InputStream and returns a string representation of it.

package org.kodejava.commons.io;

import org.apache.commons.io.IOUtils;

import java.io.InputStream;
import java.io.FileInputStream;
import java.nio.charset.StandardCharsets;

public class InputStreamToString {
    public static void main(String[] args) throws Exception {
        // Create an input stream for reading data.txt file content.
        try (InputStream is = new FileInputStream("data.txt")) {
            // Get the content of an input stream as a string using UTF-8
            // as the character encoding.
            String contents = IOUtils.toString(is, StandardCharsets.UTF_8);
            System.out.println(contents);
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.16.1</version>
</dependency>