How can Spring Boot call a third-party API to fetch a file stream?

2 years ago
Sophia Anderson
2 minutes

To call a third-party API and retrieve a file stream, you can follow these steps:

  1. RestTemplate is a tool used in Java for making HTTP requests and consuming RESTful web services.
  2. The HttpComponentsClientHttpRequestFactory
<dependencies>
    <!-- RestTemplate -->
    <dependency>
        <groupId>org.springframework.boot</groupId>
        <artifactId>spring-boot-starter-web</artifactId>
    </dependency>
    <!-- HttpClient -->
    <dependency>
        <groupId>org.apache.httpcomponents</groupId>
        <artifactId>httpclient</artifactId>
    </dependency>
</dependencies>
  1. The RestTemplate is a tool used for making RESTful API calls.
  2. HttpRequestFactory provided by the HttpComponents client library
@Configuration
public class RestTemplateConfig {
    @Bean
    public RestTemplate restTemplate() {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpComponentsClientHttpRequestFactory factory = new HttpComponentsClientHttpRequestFactory(httpClient);
        return new RestTemplate(factory);
    }
}
  1. Template for making requests.
@Autowired
private RestTemplate restTemplate;
  1. a template for making RESTful API requests
public InputStream getRemoteFile(String url) {
    ResponseEntity<Resource> response = restTemplate.getForEntity(url, Resource.class);
    Resource resource = response.getBody();
    try {
        return resource.getInputStream();
    } catch (IOException e) {
        e.printStackTrace();
    }
    return null;
}

In the code above, the variable “url” is the URL of a third-party API, which is passed as a parameter to the getRemoteFile method. This method uses restTemplate.getForEntity to send a GET request and returns the file stream from the response Resource object.

Note: This only applies to interfaces that return a file stream. If the file is returned as a byte array or string, adjustments can be made accordingly.

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