How to Handle File Downloads in Spring Controllers?

Downloading Files with Spring Controllers

Downloading a file from a website involves creating the file, handling user requests for the file, and sending the file to the client. This article will focus on how to handle file downloads in Spring controllers.

Creating the File

The first step is to generate the file, which can be done using a reporting library such as JasperReports or a PDF generation framework like iText. These libraries allow you to create files dynamically based on data or templates.

Handling User Requests

Once the file is created, it needs to be available for users to download. Spring controllers provide a convenient way to map user requests to actions. For file downloads, we can create a controller method that handles GET requests for a specific file name.

@RequestMapping(value = "/files/{file_name}", method = RequestMethod.GET)
public void getFile(
    @PathVariable("file_name") String fileName, 
    HttpServletResponse response) {
    // ...
}

Sending the File

In the controller method, we need to send the file to the client. This involves retrieving the file as an InputStream and copying it to the response's output stream.

InputStream is = ...;
org.apache.commons.io.IOUtils.copy(is, response.getOutputStream());

Setting the appropriate content type is also important. For PDFs, this would be:

response.setContentType("application/pdf");

By following these steps, you can create and send files for download using Spring controllers.

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