How do I create an Excel document using Apache POI?

By Wayan in Apache POI 2 Comments

This example demonstrate how to create an Excel document using Apache POI library. In this example we create a simple document containing two sheets which have a value on their first cell.

package org.kodejava.poi;

import org.apache.poi.hssf.usermodel.*;

import java.io.FileOutputStream;
import java.io.IOException;

public class CreateExcelDemo {
    public static void main(String[] args) {
        // Creating an instance of HSSFWorkbook.
        try (HSSFWorkbook workbook = new HSSFWorkbook()) {

            // Create two sheets in the Excel document and name it First Sheet and
            // Second Sheet.
            HSSFSheet firstSheet = workbook.createSheet("FIRST SHEET");
            HSSFSheet secondSheet = workbook.createSheet("SECOND SHEET");

            // Manipulate the first sheet by creating an HSSFRow which represent a
            // single row in Excel sheet, the first row started from 0 index. After
            // the row is created we create a HSSFCell in this first cell of the row
            // and set the cell value with an instance of HSSFRichTextString
            // containing the words FIRST SHEET.
            HSSFRow rowA = firstSheet.createRow(0);
            HSSFCell cellA = rowA.createCell(0);
            cellA.setCellValue(new HSSFRichTextString("FIRST SHEET"));

            HSSFRow rowB = secondSheet.createRow(0);
            HSSFCell cellB = rowB.createCell(0);
            cellB.setCellValue(new HSSFRichTextString("SECOND SHEET"));

            // To write out the workbook into a file we need to create an output
            // stream where the workbook content will be written to.
            try (FileOutputStream fos = new FileOutputStream("CreateExcelDemo.xls")) {
                workbook.write(fos);
            } catch (IOException e) {
                e.printStackTrace();
            }
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>org.apache.poi</groupId>
    <artifactId>poi</artifactId>
    <version>5.2.5</version>
</dependency>

Maven Central

How do I create a PDF document using iText PDF?

By Wayan in iText PDF 0 Comment

This example is the first example of the iText PDF series, we are going to start by learning to use the iText PDF library to create a PDF document. We will see how to use the Document class, getting an instance of PdfWriter, creating a simple Paragraph and set the text alignment and the font.

The basic steps to produce a PDF documents are:

  • Create a Document object that represents a PDF document.
  • The PdfWrite object that need the Document and an OutputStream object write the content of the PDF we added to the Document into a PDF file.
  • We add a paragraph into the Document instance using the Paragraph object.
  • Finally, we need to close the document by calling the Document.close() method.

And here is a code example that demonstrate the creation of a PDF document.

package org.kodejava.itextpdf;

import com.itextpdf.text.*;
import com.itextpdf.text.pdf.PdfWriter;

import java.io.FileNotFoundException;
import java.io.FileOutputStream;

public class DocumentCreate {
    public static void main(String[] args) {
        // Create a new document.
        Document document = new Document();
        try {
            // Get an instance of PdfWriter and create a HelloWorld.pdf
            // file as an output.
            PdfWriter.getInstance(document,
                    new FileOutputStream("HelloWorld.pdf"));
            document.open();

            // Create our first paragraph for the pdf document to be
            // created. We also set the alignment and the font of the
            // paragraph.
            String text = "Kode Java website provides beginners to Java " +
                    "programming some examples to use the Java API " +
                    "(Application Programming Interface) to develop " +
                    "applications. Learning from some examples will " +
                    "hopefully decrease the time required to learn " +
                    "Java.";
            Paragraph paragraph = new Paragraph(text);
            paragraph.setAlignment(Element.ALIGN_JUSTIFIED);
            paragraph.setFont(new Font(
                    Font.FontFamily.HELVETICA, 10, Font.NORMAL));

            document.add(paragraph);
        } catch (DocumentException | FileNotFoundException e) {
            e.printStackTrace();
        } finally {
            document.close();
        }
    }
}

Maven Dependencies

<!-- https://search.maven.org/remotecontent?filepath=com/itextpdf/itextpdf/5.5.13.3/itextpdf-5.5.13.3.jar -->
<dependency>
    <groupId>com.itextpdf</groupId>
    <artifactId>itextpdf</artifactId>
    <version>5.5.13.3</version>
</dependency>

Maven Central

How do I add query string to HttpMethod object?

By Wayan in Apache Commons, Commons HttpClient 0 Comment

To send query string information in HTTP GET command you either using passing a simple string or an array of NameValuePair object into the HttpMethod‘s setQueryString() method. We also need to encode the parameter values before passing it to the method.

package org.kodejava.commons.httpclient;

import org.apache.commons.httpclient.*;
import org.apache.commons.httpclient.util.URIUtil;
import org.apache.commons.httpclient.methods.GetMethod;

import java.io.IOException;

public class SendingQueryParameter {
    public static void main(String[] args) {
        HttpClient client = new HttpClient();
        HttpMethod method = new GetMethod("http://localhost:8080/hello.jsp");

        try {
            // Set query string information for accessing the page using a
            // simple string information.
            method.setQueryString(URIUtil.encodeQuery("catid=10&page=1"));
            client.executeMethod(method);

            // Other cleaner alternative is to use the NameValuePair object to
            // define the parameters for an HTTP GET method.
            NameValuePair param1 = new NameValuePair("catid", URIUtil.encodeQuery("20"));
            NameValuePair param2 = new NameValuePair("page", URIUtil.encodeQuery("2"));
            NameValuePair[] params = new NameValuePair[]{param1, param2};
            method.setQueryString(params);
            client.executeMethod(method);
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            method.releaseConnection();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-httpclient</groupId>
    <artifactId>commons-httpclient</artifactId>
    <version>3.1</version>
</dependency>

Maven Central

How do I set a proxy for HttpClient?

By Wayan in Apache Commons, Commons HttpClient 3 Comments

In this example you will see how to configure proxy when using the Apache Commons HttpClient library.

package org.kodejava.commons.httpclient;

import org.apache.commons.httpclient.Credentials;
import org.apache.commons.httpclient.HostConfiguration;
import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpMethod;
import org.apache.commons.httpclient.HttpStatus;
import org.apache.commons.httpclient.UsernamePasswordCredentials;
import org.apache.commons.httpclient.auth.AuthScope;
import org.apache.commons.httpclient.methods.GetMethod;

import java.io.IOException;

public class HttpGetProxy {
    private static final String PROXY_HOST = "proxy.host.com";
    private static final int PROXY_PORT = 8080;

    public static void main(String[] args) {
        HttpClient client = new HttpClient();
        HttpMethod method = new GetMethod("https://kodejava.org");

        HostConfiguration config = client.getHostConfiguration();
        config.setProxy(PROXY_HOST, PROXY_PORT);

        String username = "guest";
        String password = "s3cr3t";
        Credentials credentials = new UsernamePasswordCredentials(username, password);
        AuthScope authScope = new AuthScope(PROXY_HOST, PROXY_PORT);

        client.getState().setProxyCredentials(authScope, credentials);

        try {
            client.executeMethod(method);

            if (method.getStatusCode() == HttpStatus.SC_OK) {
                String response = method.getResponseBodyAsString();
                System.out.println("Response = " + response);
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            method.releaseConnection();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-httpclient</groupId>
    <artifactId>commons-httpclient</artifactId>
    <version>3.1</version>
</dependency>

Maven Central

How do I perform HTTP GET method?

By Wayan in Apache Commons, Commons HttpClient 0 Comment

Below is an example using Commons HttpClient library to retrieve information from a website using HTTP GET method. The response will be returned as stream by the HttpMethod.getResponseBodyAsStream() method. If you want something simple you can get the response as string by using the HttpMethod.getResponseBodyAsString() method.

package org.kodejava.commons.httpclient;

import org.apache.commons.httpclient.HttpClient;
import org.apache.commons.httpclient.HttpMethod;
import org.apache.commons.httpclient.HttpStatus;
import org.apache.commons.httpclient.methods.GetMethod;

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

public class HttpGetDemo {
    public static void main(String[] args) {
        HttpClient client = new HttpClient();
        HttpMethod method = new GetMethod("https://kodejava.org");

        try {
            client.executeMethod(method);

            if (method.getStatusCode() == HttpStatus.SC_OK) {
                InputStream is = method.getResponseBodyAsStream();

                if (is != null) {
                    Writer writer = new StringWriter();
                    char[] buffer = new char[1024];
                    try {
                        Reader reader = new BufferedReader(new InputStreamReader(is,
                                StandardCharsets.UTF_8));
                        int length;
                        while ((length = reader.read(buffer)) != -1) {
                            writer.write(buffer, 0, length);
                        }
                    } finally {
                        is.close();
                    }
                    System.out.println("Response = " + writer);
                }
            }
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            method.releaseConnection();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-httpclient</groupId>
    <artifactId>commons-httpclient</artifactId>
    <version>3.1</version>
</dependency>

Maven Central

How do I decode a Base64 encoded binary?

By Wayan in Apache Commons, Commons Codec 0 Comment 
package org.kodejava.commons.codec;

import org.apache.commons.codec.binary.Base64;

import java.util.Arrays;

public class Base64Decode {
    public static void main(String[] args) {
        String hello = "SGVsbG8gV29ybGQ=";

        // Decode a previously encoded string using decodeBase64 method and
        // passing the byte[] of the encoded string.
        byte[] decoded = Base64.decodeBase64(hello.getBytes());

        // Print the decoded array
        System.out.println(Arrays.toString(decoded));

        // Convert the decoded byte[] back to the original string and print
        // the result.
        String decodedString = new String(decoded);
        System.out.println(hello + " = " + decodedString);
    }
}

The result of our code is:

[72, 101, 108, 108, 111, 32, 87, 111, 114, 108, 100]
SGVsbG8gV29ybGQ= = Hello World

Maven Dependencies

<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.16.0</version>
</dependency>

Maven Central

How do I encode binary data as Base64 string?

By Wayan in Apache Commons, Commons Codec 0 Comment 
package org.kodejava.commons.codec;

import org.apache.commons.codec.binary.Base64;

import java.util.Arrays;

public class Base64Encode {
    public static void main(String[] args) {
        String hello = "Hello World";

        // The encodeBase64 method take a byte[] as the parameter. The byte[]
        // can be from a simple string like in this example, or it can be from
        // an image file data.
        byte[] encoded = Base64.encodeBase64(hello.getBytes());

        // Print the encoded byte array
        System.out.println(Arrays.toString(encoded));

        // Print the encoded string
        String encodedString = new String(encoded);
        System.out.println(hello + " = " + encodedString);
    }
}

The result of our program:

[83, 71, 86, 115, 98, 71, 56, 103, 86, 50, 57, 121, 98, 71, 81, 61]
Hello World = SGVsbG8gV29ybGQ=

Maven Dependencies

<dependency>
    <groupId>commons-codec</groupId>
    <artifactId>commons-codec</artifactId>
    <version>1.16.0</version>
</dependency>

Maven Central

How do I sort files based on their last modified date?

By Wayan in Apache Commons, Commons IO 0 Comment

This example demonstrates how to use Apache Commons IO LastModifiedFileComparator class to sort files based on their last modified date in ascending and descending order. There are two comparators defined in this class, the LASTMODIFIED_COMPARATOR and the LASTMODIFIED_REVERSE.

package org.kodejava.commons.io;

import static org.apache.commons.io.comparator.LastModifiedFileComparator.*;

import java.io.File;
import java.util.Arrays;

public class FileSortLastModified {
    public static void main(String[] args) {
        File dir = new File(System.getProperty("user.home"));
        File[] files = dir.listFiles();

        if (files != null) {
            // Sort files in ascending order based on file's last
            // modification date.
            System.out.println("Ascending order.");
            Arrays.sort(files, LASTMODIFIED_COMPARATOR);
            FileSortLastModified.displayFileOrder(files);

            System.out.println("------------------------------------");

            // Sort files in descending order based on file's last
            // modification date.
            System.out.println("Descending order.");
            Arrays.sort(files, LASTMODIFIED_REVERSE);
            FileSortLastModified.displayFileOrder(files);
        }
    }

    private static void displayFileOrder(File[] files) {
        for (File file : files) {
            System.out.printf("%2$td/%2$tm/%2$tY - %s%n", file.getName(),
                    file.lastModified());
        }
    }
}

Here are the example results produced by the code snippet:

Ascending order.
15/12/2020 - ntuser.dat.LOG1
15/12/2020 - ntuser.ini
15/12/2020 - .m2
18/12/2020 - Contacts
22/12/2020 - Videos
01/01/2021 - VirtualBox VMs
02/01/2021 - Desktop
02/01/2021 - Documents
------------------------------------------
Descending order.
02/01/2021 - Documents
02/01/2021 - Desktop
01/01/2021 - VirtualBox VMs
22/12/20202 - Videos
18/12/20202 - Contacts
15/12/20202 - .m2
15/12/20202 - ntuser.ini
15/12/20202 - ntuser.dat.LOG1

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.14.0</version>
</dependency>

Maven Central

How do I search for files recursively using Apache Commons IO?

By Wayan in Apache Commons, Commons IO 0 Comment

This example demonstrates how we can use the FileUtils class listFiles() method to search for a file specified by their extensions. We can also define to find the file recursively deep down into the subdirectories.

package org.kodejava.commons.io;

import org.apache.commons.io.FileUtils;

import java.io.File;
import java.util.Collection;

public class SearchFileRecursive {
    public static void main(String[] args) {
        File root = new File("F:/Wayan/Kodejava/kodejava-example");

        try {
            String[] extensions = {"xml", "java", "dat"};

            // Find files within a root directory and optionally its
            // subdirectories, which match an array of extensions. When the
            // extensions are null, all files will be returned.
            //
            // This method will return matched file as java.io.File
            Collection<File> files = FileUtils.listFiles(root, extensions, true);

            for (File file : files) {
                System.out.println("File = " + file.getAbsolutePath());
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-io</groupId>
    <artifactId>commons-io</artifactId>
    <version>2.14.0</version>
</dependency>

Maven Central

How do I delete file from FTP server?

By Wayan in Apache Commons, Commons Net 0 Comment

This example demonstrates how to delete file from FTP server.

package org.kodejava.commons.net;

import org.apache.commons.net.ftp.FTPClient;

import java.io.IOException;

public class FTPDeleteDemo {
    public static void main(String[] args) {
        FTPClient client = new FTPClient();

        try {
            client.connect("ftp.example.com");
            client.login("demo", "password");

            // Delete file on the FTP server. When the FTP delete
            // process completes, it returns true.
            String filename = "data.txt";
            boolean deleted = client.deleteFile(filename);
            if (deleted) {
                System.out.printf("File %s was deleted...", filename);
            } else {
                System.out.println("No file was deleted...");
            }

            client.logout();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                client.disconnect();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

Maven Dependencies

<dependency>
    <groupId>commons-net</groupId>
    <artifactId>commons-net</artifactId>
    <version>3.10.0</version>
</dependency>

Maven Central