Published July 6, 2023
How to Preview PDF Files in Java
Previewing PDF files is common in many Java applications, especially for document management or content distribution.
IronPDF is a powerful library that allows Java developers to work with PDF files effectively.
In this article, we will learn how to use IronPDF to preview PDF files within a Java application.
IronPDF
IronPDF is a high-performance Java library, offering fast and accurate operations, making it an excellent choice for PDF-related tasks such as to read PDF files, extract text and images, merging, and splitting.
With the help of the IronPDF library, you can create PDFs from HTML, URLs, and strings with precise pixel-perfect rendering.
Prerequisites
To create a document viewer for PDF documents in Java, you need the following things set in place.
- JDK (Java Development Kit) and Swing UI framework installed.
- A Java IDE (Integrated Development Environment) such as Eclipse, NetBeans, or IntelliJ IDEA.
- IronPDF library for Java (You can download it from the IronPDF website and include it in your project).
Setting up
- Create a new Java project in your chosen IDE. I'm using IntelliJ IDEA and created the project using Maven.
Add the IronPDF library to your project using Maven by adding the dependencies shown below in your project's pom.xml file:
<dependency>
<groupId>com.ironsoftware</groupId>
<artifactId>com.ironsoftware</artifactId>
<version>2024.3.1</version>
</dependency>Add the necessary imports:
import com.ironsoftware.ironpdf.PdfDocument; import javax.imageio.ImageIO; import javax.swing.*; import javax.swing.border.EmptyBorder; import java.awt.image.BufferedImage; import java.io.File; import java.io.IOException; import java.nio.file.Paths; import java.util.ArrayList; import java.util.List;
JAVA
Loading the PDF File Format
To view PDF documents, we need to load the PDF file in our Java PDF viewer application. We can do so using the PdfDocument
class.
public class PDFPreview extends JFrame {
private List<String> imagePaths = new ArrayList<>();
private List<String> ConvertToImages() throws IOException{
PdfDocument pdfDocument = PdfDocument.fromFile(Paths.get("example.pdf"));
// Create a list of paths for images
List<BufferedImage> extractedImages = pdfDocument.toBufferedImages();
int i = 1;
for (BufferedImage extractedImage : extractedImages) {
String fileName = "assets/images/" + i + ".png";
ImageIO.write(extractedImage, "PNG", new File(fileName));
imagePaths.add("assets/images/" + i + ".png");
i++;
}
return imagePaths;
}
}
Converted to Images:
Creating PDF Viewer Window
Now, you can display the converted images in a preview window using Java Swing components.
public class PDFPreview extends JFrame {
private JPanel imagePanel;
private JScrollPane scrollPane;
public PDFPreview(){
try{
imagePaths = this.ConvertToImages();
}
catch(Exception e){
}
// Create imagePanel
imagePanel = new JPanel();
imagePanel.setLayout(new BoxLayout(imagePanel, BoxLayout.Y_AXIS));
// Add images to the panel
for (String imagePath : imagePaths) {
ImageIcon imageIcon = new ImageIcon(imagePath);
JLabel imageLabel = new JLabel(imageIcon);
imageLabel.setBorder(new EmptyBorder(10, 10, 10, 10));
imagePanel.add(imageLabel);
}
// Create the scroll pane and add imagePanel to it
scrollPane = new JScrollPane(imagePanel);
scrollPane.setVerticalScrollBarPolicy(JScrollPane.VERTICAL_SCROLLBAR_ALWAYS);
// Set up the frame
getContentPane().add(scrollPane);
setTitle("PDF Viewer");
setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
pack();
setLocationRelativeTo(null);
setVisible(true);
}
}
Invoke the Main class Constructor
Finally, place the following code in the main method in PDFPreview
class:
public static void main(String[] args) {
SwingUtilities.invokeLater(
PDFPreview::new
);
}
Code Explanation
PDFPreview
extendsJFrame
, a top-level container for window creation.- Instance variables declared:
imagePanel
,scrollPane
, andimagePaths
. ConvertToImages()
takes in PDF fileexample.pdf
, and converts it to a series of images. ThePdfDocument
loads the PDF file and converts each page to aBufferedImage
, then saves each as a PNG in the assets/images/ directory and adds the paths toimagePaths
.PDFPreview()
initializes the application. It callsConvertToImages()
to populateimagePaths
.imagePanel
is initialized and sets its layout as vertical box layout.- It iterates over
imagePaths
and createsImageIcon
for each image, adds them toJLabel
, and adds labels toimagePanel
. - The source code creates
JScrollPane
and setsimagePanel
as its viewport. - Next, the code adds
scrollPane
to the frame's content pane, sets frame's title, sets default close operation, packs components, centers frame on the screen, and makes it visible. main()
is the entry point of the program. It invokes thePDFPreview
constructor usingSwingUtilities.invokeLater()
to ensure the Swing components are created and modified on the Event Dispatch Thread, the dedicated thread for GUI operations.
Now, execute the program and the PDF document file viewer will be displayed with the loaded PDF document.
Conclusion
In this article, we have explored how to use IronPDF for Java-based applications to preview PDF files within a Java application. We learned how to access a PDF file and display it in a Java PDF viewer window.
With IronPDF, you can easily integrate PDF preview functionality into your Java application. For detailed guidance and example on utilizing IronPDF for Java, you can refer here. For the Java PDF reader tutorial visit this link.
IronPDF is free for development purposes, to learn more about the licensing details, you can visit the provided link. A free trial for commercial use is also available.