How do I read an XML document using JDOM?

By Wayan in JDOM 0 Comment

This example provide a small code snippet on how to use JDOM to parse an XML document, iterates each of the element and read the element or attributes values. To play with this example you have to have the JDOM library. You can download it from JDOM website.

package org.kodejava.jdom;

import org.jdom2.Document;
import org.jdom2.Element;
import org.jdom2.input.SAXBuilder;

import java.io.ByteArrayInputStream;
import java.nio.charset.StandardCharsets;
import java.util.List;

public class ReadXmlDocument {
    public static void main(String[] args) {
        // Our imaginary xml file to be processed in this example.
        String data = """
                <root>
                    <row>
                        <column name="username" length="16">admin</column>
                        <column name="password" length="128">secret</column>
                    </row>
                    <row>
                        <column name="username" length="16">jdoe</column>
                        <column name="password" length="128">password</column>
                    </row>
                </root>""";

        // Create an instance of SAXBuilder
        SAXBuilder builder = new SAXBuilder();
        try {
            // Tell the SAXBuilder to build the Document object from the
            // InputStream supplied.
            Document document = builder.build(
                    new ByteArrayInputStream(data.getBytes(StandardCharsets.UTF_8)));

            // Get our xml document root element which equals to the
            // <root> tag in the xml document.
            Element root = document.getRootElement();

            // Get all the children named with <row> in the document.
            // The method return the children as a java.util.List
            // object.
            List<Element> rows = root.getChildren("row");
            for (Element row : rows) {
                // Convert each row to an Element object and get its
                // children which will return a collection of <column>
                // elements. When we have to column row we can read
                // the attribute value (name, length) as defined above
                // and also read its value (between the <column></column>
                // tag) by calling the getText() method.
                //
                // The getAttribute() method also provide a handy method
                // if we want to convert the attribute value to a correct
                // org.kodejava.data type, in the example we read the length attribute
                // value as an integer.
                List<Element> columns = row.getChildren("column");
                for (Element column : columns) {
                    String name = column.getAttribute("name").getValue();
                    String value = column.getText();
                    int length = column.getAttribute("length").getIntValue();

                    System.out.println("name = " + name);
                    System.out.println("value = " + value);
                    System.out.println("length = " + length);
                }
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

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

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How do I sort items of an ArrayList?

By Wayan in Core API, Util Package 0 Comment

This example shows you how we can sort items of an ArrayList using the Collections.sort() method. Beside accepting the list object to be sorted we can also pass a Comparator implementation to define the sorting behaviour such as sorting in descending or ascending order.

package org.kodejava.util;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;
import java.util.List;

public class ArrayListSortExample {
    public static void main(String[] args) {
        /*
         * Create a collections of colours
         */
        List<String> colours = new ArrayList<>();
        colours.add("red");
        colours.add("green");
        colours.add("blue");
        colours.add("yellow");
        colours.add("cyan");
        colours.add("white");
        colours.add("black");

        /*
         * We can sort items of a list using the Collections.sort() method.
         * We can also reverse the order of the sorting by passing the
         * Collections.reverseOrder() comparator.
         */
        Collections.sort(colours);
        System.out.println(Arrays.toString(colours.toArray()));

        colours.sort(Collections.reverseOrder());
        System.out.println(Arrays.toString(colours.toArray()));
    }
}

The code will output:

[black, blue, cyan, green, red, white, yellow]
[yellow, white, red, green, cyan, blue, black]

How do I sort array values in case-insensitive order?

By Wayan in Core API, Util Package 1 Comment

By default, when sorting an arrays the value will be ordered in case-sensitive order. This example show you how to order it in case-insensitive order.

package org.kodejava.util;

import java.util.Arrays;

public class SortArrayCaseSensitivity {
    public static void main(String[] args) {
        String[] teams = new String[5];
        teams[0] = "Manchester United";
        teams[1] = "chelsea";
        teams[2] = "Arsenal";
        teams[3] = "liverpool";
        teams[4] = "EVERTON";

        // Sort array, by default it will be sorted in case-sensitive order.
        // [Arsenal, EVERTON, Manchester United, chelsea, liverpool]
        Arrays.sort(teams);
        System.out.println("Case sensitive  : " + Arrays.toString(teams));

        // Sort array in case-insensitive order
        // [Arsenal, chelsea, EVERTON, liverpool, Manchester United]
        Arrays.sort(teams, String.CASE_INSENSITIVE_ORDER);
        System.out.println("Case insensitive: " + Arrays.toString(teams));
    }
}

The result of the code snippet above:

Case sensitive  : [Arsenal, EVERTON, Manchester United, chelsea, liverpool]
Case insensitive: [Arsenal, chelsea, EVERTON, liverpool, Manchester United]

How do I sort array values in descending order?

By Wayan in Core API, Util Package 0 Comment

Here you will find an example on how to sort the values of an array in ascending or descending order.

package org.kodejava.util;

import java.util.Arrays;
import java.util.Collections;

public class SortArrayWithOrder {
    public static void main(String[] args) {
        Integer[] points = new Integer[5];
        points[0] = 94;
        points[1] = 53;
        points[2] = 70;
        points[3] = 44;
        points[4] = 64;
        System.out.println("Original  : " + Arrays.toString(points));

        // Sort the points array, the default order is in ascending order.
        // [44, 53, 64, 70, 94]
        Arrays.sort(points);
        System.out.println("Ascending : " + Arrays.toString(points));

        // Sort the points array in descending order.
        // [94, 70, 64, 53, 44]
        Arrays.sort(points, Collections.reverseOrder());
        System.out.println("Descending: " + Arrays.toString(points));
    }
}

The result of the code snippet above are:

Original  : [94, 53, 70, 44, 64]
Ascending : [44, 53, 64, 70, 94]
Descending: [94, 70, 64, 53, 44]

How do I limit Hibernate query result?

By Wayan in Hibernate 0 Comment

In the example below you’ll see how to limit the number of records returned by hibernate queries. Limiting the query result is usually use for creating pagination, where we can navigate from page to page of data in our application but only a few of them are read from the database.

In hibernate Query object we need to specify the first result and max results by calling the setFirstResult() and setMaxResults() methods to limit the query results.

package org.kodejava.hibernate.service;

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

import java.util.List;

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

        Query<Label> query = session.createQuery("from Label", Label.class);

        // Set the first record position and the max number of record to be
        // read. The setFirstResult() tell hibernate from which row the data
        // should be read. In the example if we have pages of 10 records,
        // passing the page number 2 will read 10 records from the 20th row
        // in the selected records.
        query.setFirstResult((pageNumber - 1) * pageSize);
        query.setMaxResults(pageSize);

        List<Label> labels = query.list();
        session.getTransaction().commit();
        return labels;
    }
}

package org.kodejava.hibernate;

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

import java.util.List;

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

        List<Label> labels = service.getLabels(1, 10);
        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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