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

Question

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?

Answer 1

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();

Answer 2

You can use WebClient:

byte[] image = WebClient.create("locahost:80/image.jpg")
        .get()
        .accept(MediaType.IMAGE_JPEG)
        .retrieve()
        .bodyToMono(byte[].class)
        .block();

Answer 3

If you want to send a request with spring you can do

//first create e restemplate variable
RestTemplate restTemplate=new RestTemplate();

//you can create and edit header
HttpHeaders header= new HttpHeaders();
header.add("Authorization", "*****************");
header.setContentType(MediaType.APPLICATION_FORM_URLENCODED);
header.add("Accept", "application/json");

//you can create and edit body to
MultiValueMap<String, String> body= new LinkedMultiValueMap<String, String>();
body.add("grant_type", "client_credentials");

HttpEntity<MultiValueMap<String, String>> requeteHttp =new HttpEntity<MultiValueMap<String, String>>(body, header);

//After you can create a request
ResponseEntity<Response_class> reponse = restTemplate.postForEntity("your api link", requeteHttp , Response_class.class);
//if you want to send a get request you can edit postForEntity to get

About Response_class if you know the return type of the request, you can create a class and use it here, otherwise you can use string instead

if your request returns a json like this

{
    "token_type":"***",
    "access_token":"***",
    "expires_in":"***",
}

you can create a Response_class controller(class) and call it like we did above otherwise you can use string instead

public class Response_class{
    private String token_type;
    private String access_token;
    private String expires_in;

    public Response_class(String token_type, String access_token, String expires_in) {
        this.token_type = token_type;
        this.access_token = access_token;
        this.expires_in = expires_in;
    }

    public Response_class() {
    }

    public String getToken_type() {
        return token_type;
    }

    public void setToken_type(String token_type) {
        this.token_type = token_type;
    }

    public String getAccess_token() {
        return access_token;
    }

    public void setAccess_token(String access_token) {
        this.access_token = access_token;
    }

    public String getExpires_in() {
        return expires_in;
    }

    public void setExpires_in(String expires_in) {
        this.expires_in = expires_in;
    }


}