Apache Wicket is a powerful Java web framework that enables the development of rich and interactive web applications. One common requirement in many web applications is the ability to generate and display PDF documents. In this blog post, we will explore how to implement PDF generation in Apache Wicket applications.

Prerequisites

Before we begin, make sure you have the following prerequisites in place:

• Apache Wicket installed and configured in your development environment.
• A basic understanding of Java programming and Apache Wicket concepts.

Adding the PDF library

To generate PDF documents in Apache Wicket, we need to add a PDF library to our project. One popular and widely-used library is Apache PDFBox. Start by adding the PDFBox dependency to your project’s pom.xml file:

<dependency>
    <groupId>org.apache.pdfbox</groupId>
    <artifactId>pdfbox</artifactId>
    <version>2.0.24</version>
</dependency>

Make sure to update the version number to the latest stable release available.

Creating a PDF generation service

To generate PDF documents, we will create a service class that encapsulates the logic for creating the PDF. Create a new class called PdfGenerationService and add the following code:

import org.apache.pdfbox.pdmodel.PDDocument;
import org.apache.pdfbox.pdmodel.PDPage;
import org.apache.wicket.request.IRequestHandler;
import org.apache.wicket.request.handler.resource.ResourceStreamRequestHandler;
import org.apache.wicket.util.resource.ByteArrayResourceStream;

public class PdfGenerationService {

    public IRequestHandler generatePdf() {
        try (PDDocument document = new PDDocument()) {
            PDPage page = new PDPage();
            document.addPage(page);
    
            // Add content to the PDF document using PDFBox APIs
    
            // Save the document to a byte array
            ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
            document.save(byteArrayOutputStream);
    
            // Create a resource stream from the byte array
            ByteArrayResourceStream resourceStream = new ByteArrayResourceStream(byteArrayOutputStream.toByteArray(), "application/pdf");
    
            // Return a request handler that will download the generated PDF
            return new ResourceStreamRequestHandler(resourceStream, "generated.pdf");
        } catch (Exception e) {
            // Handle exception appropriately
        }
        return null;
    }
}

The generatePdf() method creates a new PDF document using PDFBox APIs and saves it to a byte array. We then create a resource stream from the byte array and return a request handler that will download the generated PDF.

Generating PDF on button click

To generate the PDF when a button is clicked in your Apache Wicket application, we need to add a Button component to our page and attach a ClickEvent to it. Here’s an example of how to do it:

public class HomePage extends WebPage {

    public HomePage(PageParameters parameters) {
        super(parameters);

        add(new Button("pdfButton") {
            @Override
            public void onSubmit() {
                super.onSubmit();
                PdfGenerationService pdfGenerationService = new PdfGenerationService();
                getRequestCycle().scheduleRequestHandlerAfterCurrent(pdfGenerationService.generatePdf());
            }
        });
    }
}

In this example, we create a new Button component with the ID “pdfButton” and override its onSubmit() method. Inside the onSubmit() method, we create an instance of PdfGenerationService and schedule the request handler returned by generatePdf().

Conclusion

In this blog post, we have seen how to implement PDF generation in Apache Wicket applications using the Apache PDFBox library. By creating a PDF generation service and attaching it to a button click event, we can easily generate and download PDF documents within our Wicket applications. Experiment with the code and explore additional features and formatting options provided by PDFBox to enhance your PDF generation capabilities.

#PDF #ApacheWicket