How to Call a REST API in Spring Boot?

To call a REST API in Spring Boot, you can use the RestTemplate class provided by the Spring Framework. Here's a basic example:

1. Create an instance of RestTemplate:

    RestTemplate restTemplate = new RestTemplate();
    

2. Define the endpoint and any necessary request parameters:

String url = "https://example.com/api/data";

UriComponentsBuilder builder = UriComponentsBuilder.fromUriString(url)
		    .queryParam("param1", "value1")
		    .queryParam("param2", "value2")
		    .queryParam("param3", "value3")
		    .queryParam("param4", "value4");

3. Send the HTTP request and receive response:

HttpHeaders headers = new HttpHeaders();
headers.set("Accept", MediaType.APPLICATION_JSON_VALUE);
HttpEntity<String> httpEntity = new HttpEntity<>(headers);

ResponseEntity<String> response = restTemplate.exchange(builder.toUriString(), HttpMethod.GET, 
    httpEntity, String.class);
		
if(response.getStatusCode().is2xxSuccessful()) {
	//success
	String data = response.getBody();
			
} else {
	//fail
}    

In this example, we are using the exchange method of RestTemplate to send a GET request to the specified URL with the query parameters. The method returns a ResponseEntity object, which contains the response status code, headers, and body.

You can also use other HTTP methods like POST, PUT, DELETE, etc., by calling the appropriate methods of RestTemplate. Additionally, you can configure RestTemplate to handle things like authentication, message conversion, and error handling, by creating a RestTemplate bean and configuring it with appropriate settings in your Spring Boot configuration file.

Overall, using RestTemplate in Spring Boot is a convenient and flexible way to call REST APIs and integrate them into your application.