Kode Java - Learn Java by Examples

How do I store properties as XML file?

By Wayan in Core API, IO Last modified: May 18, 2023 0 Comment

In the previous example, How do I load properties from XML file? we read properties from XML file. Now it’s the turn on how to store the properties as XML file.

package org.kodejava.io;

import java.io.FileOutputStream;
import java.nio.charset.StandardCharsets;
import java.util.Properties;

public class PropertiesToXml {
    public static void main(String[] args) throws Exception {
        Properties properties = new Properties();
        properties.setProperty("db.type", "mysql");
        properties.setProperty("db.url", "jdbc:mysql://localhost:3306/kodejava");
        properties.setProperty("db.username", "root");
        properties.setProperty("db.password", "");

        FileOutputStream fos = new FileOutputStream("db-config.xml");
        properties.storeToXML(fos, "Database Configuration", StandardCharsets.UTF_8);
    }
}

The saved XML file will look like the properties file below:

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<properties>
    <comment>Database Configuration</comment>
    <entry key="db.type">mysql</entry>
    <entry key="db.password"></entry>
    <entry key="db.username">root</entry>
    <entry key="db.url">jdbc:mysql://localhost:3306/kodejava</entry>
</properties>

How do I load properties from XML file?

By Wayan in Core API, Util Package Last modified: May 18, 2023 0 Comment

Reading XML properties can be easily done using the java.util.Properties.loadFromXML() method. Just like reading the properties from a file that contains a key=value pairs, the XML file will also contain a key and value wrapped in the following XML format.

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE properties SYSTEM "http://java.sun.com/dtd/properties.dtd">
<properties>
    <comment>Application Configuration</comment>
    <entry key="data.folder">D:\AppData</entry>
    <entry key="jdbc.url">jdbc:mysql://localhost/kodejava</entry>
</properties>

package org.kodejava.util;

import java.util.Properties;

public class LoadXmlProperties {
    public static void main(String[] args) {
        LoadXmlProperties demo = new LoadXmlProperties();
        try {
            Properties properties = demo.readProperties();

            //Display all properties information
            properties.list(System.out);

            // Read the value of data.folder and jdbc.url configuration
            String dataFolder = properties.getProperty("data.folder");
            System.out.println("data.folder = " + dataFolder);
            String jdbcUrl = properties.getProperty("jdbc.url");
            System.out.println("jdbc.url    = " + jdbcUrl);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }

    private Properties readProperties() throws Exception {
        Properties properties = new Properties();
        properties.loadFromXML(getClass().getResourceAsStream("/configuration.xml"));
        return properties;
    }
}

The result of the code snippet above:

-- listing properties --
data.folder=D:\AppData
jdbc.url=jdbc:mysql://localhost/kodejava
data.folder = D:\AppData
jdbc.url    = jdbc:mysql://localhost/kodejava

How do I convert InputStream to String?

By Wayan in Core API, IO Last modified: May 18, 2023 1 Comment

This example will show you how to convert an InputStream into String. In the code snippet below we read a data.txt file, could be from common directory or from inside a jar file.

package org.kodejava.io;

import java.io.*;
import java.nio.charset.StandardCharsets;

public class StreamToString {

    public static void main(String[] args) throws Exception {
        StreamToString demo = new StreamToString();

        // Get input stream of our data file. This file can be in
        // the root of your application folder or inside a jar file
        // if the program is packed as a jar.
        InputStream is = demo.getClass().getResourceAsStream("/student.csv");

        // Call the method to convert the stream to string
        System.out.println(demo.convertStreamToString(is));
    }

    private String convertStreamToString(InputStream stream) throws IOException {
        // To convert the InputStream to String we use the
        // Reader.read(char[] buffer) method. We iterate until the
        // Reader return -1 which means there's no more data to
        // read. We use the StringWriter class to produce the string.
        if (stream != null) {
            Writer writer = new StringWriter();

            char[] buffer = new char[1024];
            try (stream) {
                Reader reader = new BufferedReader(new InputStreamReader(stream,
                        StandardCharsets.UTF_8));
                int length;
                while ((length = reader.read(buffer)) != -1) {
                    writer.write(buffer, 0, length);
                }
            }
            return writer.toString();
        }
        return "";
    }
}

How do I convert string into InputStream?

By Wayan in Core API, IO Last modified: May 18, 2023 0 Comment

Here you will find how to convert string into java.io.InputStream object using java.io.ByteArrayInputStream class.

package org.kodejava.io;

import java.io.*;
import java.nio.charset.StandardCharsets;

public class StringToStream {
    public static void main(String[] args) {
        String text = "Converting String to InputStream Example";

        // Convert String to InputStream using ByteArrayInputStream
        // class. This class constructor takes the string byte array
        // which can be done by calling the getBytes() method.
        InputStream stream = new ByteArrayInputStream(text.getBytes(StandardCharsets.UTF_8));
    }
}

How do I determine bean’s property type?

By Wayan in Apache Commons, Commons Beanutils Last modified: May 18, 2023 0 Comment

Using the PropertyUtils.getPropertyType() we can determine the bean property type. This method return a Class object of bean’s property type.

package org.kodejava.commons.beanutils;

import org.apache.commons.beanutils.PropertyUtils;
import org.kodejava.commons.beanutils.support.Record;

public class PropertyType {
    public static void main(String[] args) {
        Record record = new Record();
        record.setTitle("Magical Mystery Tour");

        try {
            /*
             * Using PropertyUtils.getPropertyType() to determine the type of
             * title property.
             */
            Class<?> type = PropertyUtils.getPropertyType(record, "title");
            System.out.println("type = " + type.getName());

            String value = (String) PropertyUtils.getProperty(record, "title");
            System.out.println("value = " + value);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

package org.kodejava.commons.beanutils.support;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Record {
    private Long id;
    private String title;
    private List<Track> tracks = new ArrayList<>();
    private Map<String, Track> mapTracks = new HashMap<>();

    public Long getId() {
        return id;
    }

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

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public List<Track> getTracks() {
        return tracks;
    }

    public void setTracks(List<Track> tracks) {
        this.tracks = tracks;
    }

    public void setMapTracks(Map<String, Track> mapTracks) {
        this.mapTracks = mapTracks;
    }

    public Map<String, Track> getMapTracks() {
        return mapTracks;
    }
}

The output of the code snippet above:

type = java.lang.String
value = Magical Mystery Tour

Maven Dependencies

<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.4</version>
</dependency>

How do I read mapped bean’s property value?

By Wayan in Apache Commons, Commons Beanutils Last modified: May 18, 2023 0 Comment

In this example you’ll see how to read mapped property value of a bean. We use PropertyUtils.getMappedProperty() method the read the mapped property of the Record object that consist of Track objects.

package org.kodejava.commons.beanutils;

import org.apache.commons.beanutils.PropertyUtils;
import org.kodejava.commons.beanutils.support.Track;
import org.kodejava.commons.beanutils.support.Record;

import java.util.HashMap;
import java.util.Map;

public class ReadMapProperty {
    public static void main(String[] args) {
        Record record = new Record();
        record.setTitle("Abbey Road");

        Track track1 = new Track();
        track1.setTitle("Come Together");

        Track track2 = new Track();
        track2.setTitle("Something");

        Map<String, Track> tracks = new HashMap<>();
        tracks.put("1", track1);
        tracks.put("2", track2);

        record.setMapTracks(tracks);

        try {
            Track track = (Track) PropertyUtils.getMappedProperty(record, "mapTracks(1)");
            System.out.println("track.getTitle() = " + track.getTitle());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

package org.kodejava.commons.beanutils;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;

public class Record {
    private Long id;
    private String title;
    private List<Track> tracks = new ArrayList<>();
    private Map<String, Track> mapTracks = new HashMap<>();

    public Long getId() {
        return id;
    }

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

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public List<Track> getTracks() {
        return tracks;
    }

    public void setTracks(List<Track> tracks) {
        this.tracks = tracks;
    }

    public void setMapTracks(Map<String, Track> mapTracks) {
        this.mapTracks = mapTracks;
    }

    public Map<String, Track> getMapTracks() {
        return mapTracks;
    }
}

And here is the result of our program.

track.getTitle() = Come Together

Maven Dependencies

<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.4</version>
</dependency>

How do I read indexed bean’s property value?

By Wayan in Apache Commons, Commons Beanutils Last modified: May 18, 2023 0 Comment

In this example you’ll see how to read an indexed property of an object such as List or array. Using the PropertyUtils.getIndexedProperty() method we can do it easily. This method take the bean and the name of indexed property including the element to be read. Let’s see the example below for more details.

package org.kodejava.commons.beanutils;

import org.apache.commons.beanutils.PropertyUtils;
import org.kodejava.commons.beanutils.support.Track;
import org.kodejava.commons.beanutils.support.Record;

import java.util.ArrayList;
import java.util.List;

public class ReadIndexedProperty {
    public static void main(String[] args) {
        Record record = new Record();
        record.setId(1L);
        record.setTitle("Sgt. Pepper's Lonely Hearts Club Band");

        List<Track> tracks = new ArrayList<>();
        Track track1 = new Track();
        track1.setTitle("Sgt. Pepper's Lonely Hearts Club Band");

        Track track2 = new Track();
        track2.setTitle("With A Little Help From My Friends");

        Track track3 = new Track();
        track3.setTitle("Lucy In The Sky With Diamonds");

        tracks.add(track1);
        tracks.add(track2);
        tracks.add(track3);

        record.setTracks(tracks);

        try {
            Track trackOne = (Track) PropertyUtils.getIndexedProperty(record, "tracks[0]");
            Track trackThree = (Track) PropertyUtils.getIndexedProperty(record, "tracks[2]");

            System.out.println("trackOne.getTitle() = " + trackOne.getTitle());
            System.out.println("trackThree.getTitle() = " + trackThree.getTitle());
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

package org.kodejava.commons.beanutils.support;

import java.util.ArrayList;
import java.util.List;

public class Record {
    private Long id;
    private String title;
    private List<Track> tracks = new ArrayList<>();

    public Long getId() {
        return id;
    }

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

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public List<Track> getTracks() {
        return tracks;
    }

    public void setTracks(List<Track> tracks) {
        this.tracks = tracks;
    }
}

Our program results are:

trackOne.getTitle() = Sgt. Pepper's Lonely Hearts Club Band
trackThree.getTitle() = Lucy In The Sky With Diamonds

Maven Dependencies

<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.4</version>
</dependency>

How do I read bean’s nested property value?

By Wayan in Apache Commons, Commons Beanutils Last modified: May 18, 2023 0 Comment

In this example you’ll see how to read bean’s nested property, we’ll use PropertyUtils.getNestedProperty() method. To test we will create three classes, Track and Artist for our beans and ReadNestedProperty as a main program to run.

The Track class will contain a property of an Artist object. Using the PropertyUtils.getNestedProperty() method we want to get the artist name that sings the track. This method will first read the artist property from the track object and then read the name property of the artist object.

Reading nested property using PropertyUtils.getNestedProperty() it can read nested level in no limit.

package org.kodejava.commons.beanutils;

import org.apache.commons.beanutils.PropertyUtils;
import org.kodejava.commons.beanutils.support.Artist;
import org.kodejava.commons.beanutils.support.Track;

public class ReadNestedProperty {
    public static void main(String[] args) {
        Track track = new Track();
        track.setId(1L);
        track.setTitle("Lucy In The Sky With Diamonds");
        track.setArtist(new Artist(1L, "The Beatles"));

        try {
            String artistName = (String) PropertyUtils.getNestedProperty(track, "artist.name");
            System.out.println("Artist Name = " + artistName);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

package org.kodejava.commons.beanutils.support;

public class Track {
    private Long id;
    private String title;
    private Integer duration;
    private Artist artist;

    public Long getId() {
        return id;
    }

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

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public Integer getDuration() {
        return duration;
    }

    public void setDuration(Integer duration) {
        this.duration = duration;
    }

    public Artist getArtist() {
        return artist;
    }

    public void setArtist(Artist artist) {
        this.artist = artist;
    }

    @Override
    public String toString() {
        return "Track{" +
                "id=" + id +
                ", title='" + title + '\'' +
                ", duration=" + duration +
                '}';
    }
}

package org.kodejava.commons.beanutils.support;

public class Artist {
    private Long id;
    private String name;

    public Artist() {
    }

    public Artist(Long id, String name) {
        this.id = id;
        this.name = name;
    }

    public Long getId() {
        return id;
    }

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

    public String getName() {
        return name;
    }

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

Maven Dependencies

<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.4</version>
</dependency>

How do I read bean’s property value?

By Wayan in Apache Commons, Commons Beanutils Last modified: May 18, 2023 0 Comment

In this example we will learn how to use PropertyUtils.getSimpleProperty() method to read bean’s property value. To test this method we will create a simple class called Track for our bean. The Track class have some properties such as id, title and duration.

The PropertyUtils.getSimpleProperty() reads our bean property by accessing the bean’s getter method. The method takes two parameters. The first parameter is the bean and the second parameter is the bean’s property name. It returns a java.lang.Object as a result, that means we have to cast it to the desired type.

package org.kodejava.commons.beanutils;

import org.apache.commons.beanutils.PropertyUtils;
import org.kodejava.commons.beanutils.support.Track;

public class ReadBeanProperty {
    public static void main(String[] args) {
        Track track = new Track();
        track.setTitle("Here Comes The Sun");

        try {
            String title = (String) PropertyUtils.getSimpleProperty(track, "title");
            System.out.println("Track title = " + title);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

And here is the Track class.

package org.kodejava.commons.beanutils.support;

public class Track {
    private Long id;
    private String title;
    private Integer duration;

    public Long getId() {
        return id;
    }

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

    public String getTitle() {
        return title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public Integer getDuration() {
        return duration;
    }

    public void setDuration(Integer duration) {
        this.duration = duration;
    }

    @Override
    public String toString() {
        return "Track{" +
                "id=" + id +
                ", title='" + title + '\'' +
                ", duration=" + duration +
                '}';
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-beanutils</groupId>
    <artifactId>commons-beanutils</artifactId>
    <version>1.9.4</version>
</dependency>

How do I find text between two strings?

By Wayan in Apache Commons, Commons Lang Last modified: June 3, 2024 2 Comments

In this example we’ll use the StringUtils.substringBetween() method. Here we’ll extract the title and body of our HTML document. Let’s see the code.

package org.kodejava.commons.lang;

import java.util.Date;

import org.apache.commons.lang3.StringUtils;

public class NestedString {
    public static void main(String[] args) {
        String helloHtml = "<html>" +
                "<head>" +
                "   <title>Hello World from Java</title>" +
                "<body>" +
                "Hello, today is: " + new Date() +
                "</body>" +
                "</html>";

        String title = StringUtils.substringBetween(helloHtml, "<title>", "</title>");
        String content = StringUtils.substringBetween(helloHtml, "<body>", "</body>");

        System.out.println("title = " + title);
        System.out.println("content = " + content);
    }
}

By printing out the title and content, we’ll see something similar to:

title = Hello World from Java
content = Hello, today is: Thu Sep 30 06:32:32 CST 2021

Maven Dependencies

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