In this post, we'll go over how to implement a file download in a Spring Boot application.
We'll start by looking at the requirements for our file downloader. We'll then implement a simple file downloader using the Spring Boot framework. Finally, we'll test our file downloader to make sure it works as expected.
Our file downloader will need to meet the following requirements:
We'll start by creating a new Spring Boot project. We'll then add the following dependencies to our project:
Our file downloader will be a simple web application. We'll use Thymeleaf to render our HTML templates.
Next, we'll create a new controller class. This controller will contain the methods that our file downloader will use to download files.
We'll start by implementing a method that downloads a file from a URL. This method will take a URL as a parameter and return a File object.
@RequestMapping("/download")
public File downloadFile(String url) {
// TODO: implement file download
}
We'll use the Java URL class to download the file from the given URL. We'll then return a File object that contains the downloaded file.
Next, we'll implement a method that downloads a file of a given type. This method will take a file type as a parameter and return a File object.
@RequestMapping("/download")
public File downloadFile(String type) {
// TODO: implement file download
}
We'll use the Java URLConnection class to download the file of the given type. We'll then return a File object that contains the downloaded file.
Finally, we'll implement a method that downloads a large file. This method will take a URL and a file size as parameters and return a File object.
@RequestMapping("/download")
public File downloadFile(String url, long size) {
// TODO: implement file download
}
We'll use the Java HttpURLConnection class to download the large file from the given URL. We'll then return a File object that contains the downloaded file.
We'll now write some unit tests to test our file downloader.
First, we'll write a test that downloads a small file. This test will take a URL and a file size as parameters and return a File object.
@Test
public void testDownloadFile() {
String url = "http://example.com/file.txt";
long size = 100;
File file = downloader.downloadFile(url, size);
assertThat(file).isNotNull();
assertThat(file.length()).isEqualTo(size);
}
Next, we'll write a test that downloads a large file. This test will take a URL and a file size as parameters and return a File object.
@Test
public void testDownloadLargeFile() {
String url = "http://example.com/file.txt";
long size = 100000;
File file = downloader.downloadFile(url, size);
assertThat(file).isNotNull();
assertThat(file.length()).isEqualTo(size);
}
Finally, we'll write a test that downloads a file of a given type. This test will take a file type as a parameter and return a File object.
@Test
public void testDownloadFileOfType() {
String type = "pdf";
File file = downloader.downloadFile(type);
assertThat(file).isNotNull();
assertThat(file.getName()).endsWith(".pdf");
}
In this post, we've gone over how to implement a file download in a Spring Boot application. We've also seen how to write some unit tests to test our file downloader.