How to perform an http request to another server from spring boot controller

How do I perform a GET HTTP request from my spring boot application hosted on localhost:8080 on a server hosted on localhost:80.

For example, how do I get an image hosted at locahost:80/image.jpg from my spring application?

There are two ways you can make a third party external api request.

1. RestTemplate

        RestTemplate restTemplate = new RestTemplate();
   
        String uri = localhost:80; // or any other uri
   
        HttpHeaders headers = new HttpHeaders();
        headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
        headers.add("user-agent", "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/54.0.2840.99 Safari/537.36");
   
        HttpEntity<String> entity = new HttpEntity<>("parameters", headers);
        ResponseEntity<?> result =
                restTemplate.exchange(uri, HttpMethod.GET, entity, returnClass);
        return result.getBody();
   

If you want to get images then use following method:

String url = "http://img.championat.com/news/big/l/c/ujejn-runi_1439911080563855663.jpg";
byte[] imageBytes = restTemplate.getForObject(url, byte[].class);
Files.write(Paths.get("image.jpg"), imageBytes);

You will also need to configure ByteArrayHttpMessageConverter in application config:

@Bean
public RestTemplate restTemplate(List<HttpMessageConverter<?>> messageConverters) {
    return new RestTemplate(messageConverters);
}

@Bean
public ByteArrayHttpMessageConverter byteArrayHttpMessageConverter() {
    return new ByteArrayHttpMessageConverter();
}

2. Unirest Add unirest dependency in pom:

<!-- Unirest java -->
    <dependency>
      <groupId>com.mashape.unirest</groupId>
      <artifactId>unirest-java</artifactId>
      <version>${unirest.java.version}</version>
    </dependency>

Code to call api:

HttpResponse<JsonNode> jsonResponse = Unirest.get(your_get_url_in_string)
                    .header("header_string", "header_value")
                    .queryString("query", "query_if_any")
                    .asJson();
JsonNode responseBody = jsonResponse.getBody();