Java | Spring boot | Download a PDF file from a URL in the

Here is a Spring boot service written in Java for downloading a PDF file available on a public URL.

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import org.springframework.scheduling.annotation.Async;
import org.springframework.stereotype.Service;
import java.io.*;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

@Service
public class PdfFileDownloadService {
    @Async
    public void load(String url){
        try {
            URL pdfUrl = new URL(url);
            URLConnection urlConnection = pdfUrl.openConnection();
            if (!urlConnection.getContentType().equalsIgnoreCase("application/pdf")){
                return;
            }

            FileOutputStream outputStream = new FileOutputStream("E:\\Downloads\output.pdf");
            byte[] byteArray = new byte[1024]; // amount of bytes reading from input stream at a given time
            int readLength;

            InputStream inputStream = pdfUrl.openStream();
            while ((readLength = inputStream.read(byteArray)) > 0){
                outputStream.write(byteArray, 0, readLength);
            }

            outputStream.flush();
            outputStream.close();
            inputStream.close();
        }
        catch (FileNotFoundException e) {
            // File Not Found
        }
        catch (MalformedURLException e) {
            // URL Invalid
        }
        catch (IOException e) {
            // I/O
        }
        catch (Exception e) {
            // Exception
        }
    }
}

Code Explanation

(Chat GPT)

The @Service annotation from the Spring framework indicates that this class is a Spring-managed service.

load() method: This is the main method of the service responsible for loading a PDF file from a given URL and saving it to the local filesystem. It takes one parameter: url (the URL of the PDF file). The method is annotated with @Async, which indicates that it will be executed asynchronously.

Inside the method:

• The URL is transformed into a URL object (pdfUrl).
• A connection to the URL is established using URLConnection.
• The content type of the resource is checked to ensure it’s a PDF file.
• If the content type is not a PDF, the method returns.
• A FileOutputStream is created to write the downloaded content to a file.
• The PDF content is read from the URL’s input stream and written to the output stream.

This code demonstrates a service responsible for downloading PDF files from URLs. It uses Spring’s asynchronous processing for potentially better performance and responsiveness.