Apache Wicket is a popular Java web framework that simplifies the development of web applications. One common requirement in web applications is the ability to download files. In this blog post, I will explain how to implement file download functionality in Apache Wicket.

Prerequisites

Before we begin, make sure you have the following dependencies added to your Apache Wicket project:

<dependency>
    <groupId>org.apache.wicket</groupId>
    <artifactId>wicket-core</artifactId>
    <version>9.3.0</version>
</dependency>
<dependency>
    <groupId>org.apache.wicket</groupId>
    <artifactId>wicket-request</artifactId>
    <version>9.3.0</version>
</dependency>

Creating a DownloadPage

To implement file download functionality, we will start by creating a new Wicket WebPage called DownloadPage. This page will handle the file download request and stream the file back to the user.

public class DownloadPage extends WebPage {

    public DownloadPage(final IModel<File> fileModel) {
        IResourceStream resourceStream = new FileResourceStream(fileModel.getObject());
        String fileName = fileModel.getObject().getName();
        
        getRequestCycle().scheduleRequestHandlerAfterCurrent(
                new ResourceStreamRequestHandler(resourceStream)
                .setFileName(fileName));
    }
}

In the constructor of DownloadPage, we create a FileResourceStream based on the file model provided. We also extract the file name from the File object.

Next, we use ResourceStreamRequestHandler to handle the file download request. We set the fileName using the extracted file name and schedule the ResourceStreamRequestHandler to be executed after the current request cycle.

Setting up the File Download Link

To trigger the file download, we need to create a link in another page or component. Here’s an example of how to create a file download link using BookmarkablePageLink:

public class HomePage extends WebPage {

    public HomePage() {
        IModel<File> fileModel = Model.of(new File("/path/to/my/file.txt"));
        
        BookmarkablePageLink<Void> downloadLink = new BookmarkablePageLink<>("downloadLink", DownloadPage.class, fileModel);
        add(downloadLink);
    }
}

In the HomePage class, we create a BookmarkablePageLink called downloadLink, which points to the DownloadPage and passes the fileModel as a parameter.

Conclusion

With just a few lines of code, we were able to implement file download functionality in Apache Wicket. The DownloadPage handles the file download request and the BookmarkablePageLink triggers the download from another page or component.

Now, you can integrate file downloading into your Apache Wicket web applications with ease. Happy coding!

#Wicket #FileDownload