Month: May 2023

To make an API call from a Spring Boot application, you can use the RestTemplate or WebClient class provided by Spring. These classes offer methods for making HTTP requests and handling the responses. Here’s how you can make an API call using RestTemplate:

1. Add the necessary dependency to your pom.xml file if you haven’t already done so. The RestTemplate class is available in the spring-web module, so make sure you have the following dependency:

<dependency>
    <groupId>org.springframework.boot</groupId>
    <artifactId>spring-boot-starter-web</artifactId>
</dependency>

2. In your Spring Boot application, create an instance of RestTemplate and use its methods to make the API call. You can inject it as a dependency in your class or create a new instance.

@RestController
public class MyRestController {

    private final RestTemplate restTemplate;

    public MyRestController(RestTemplate restTemplate) {
        this.restTemplate = restTemplate;
    }

    @GetMapping("/api/call")
    public String makeAPICall() {
        String apiUrl = "https://api.example.com/endpoint";
        ResponseEntity<String> response = restTemplate.getForEntity(apiUrl, String.class);
        return response.getBody();
    }
}

3. In the above example, the makeAPICall() method sends a GET request to the specified API endpoint (https://api.example.com/endpoint) and retrieves the response as a ResponseEntity object. You can then extract the response body using response.getBody() and return it from the endpoint.
4. By default, RestTemplate uses a simple HTTP connection pool and blocking I/O. If you’re using Spring Boot 2.1 or later, it’s recommended to use WebClient instead of RestTemplate. The WebClient class is non-blocking and provides a more flexible and reactive approach to making API calls.

@RestController
public class MyRestController {

    private final WebClient webClient;

    public MyRestController(WebClient.Builder webClientBuilder) {
        this.webClient = webClientBuilder.build();
    }

    @GetMapping("/api/call")
    public Mono<String> makeAPICall() {
        String apiUrl = "https://api.example.com/endpoint";
        return webClient.get()
                .uri(apiUrl)
                .retrieve()
                .bodyToMono(String.class);
    }
}

5. In the WebClient example, the makeAPICall() method returns a Mono<String> instead of a plain String. Mono is a reactive type that represents a potentially asynchronous result. You can handle it asynchronously using reactive programming techniques.

These are the basic steps to make an API call from a Spring Boot application. Depending on your requirements, you can customize the request headers, handle request parameters, handle error responses, and perform other operations using the available methods of RestTemplate or WebClient.