How to set an “Accept:” header on Spring RestTempl

Question

I want to set the value of the Accept: in a request I am making using Spring's RestTemplate.

Here is my Spring request handling code

@RequestMapping(
    value= "/uom_matrix_save_or_edit", 
    method = RequestMethod.POST,
    produces="application/json"
)
public @ResponseBody ModelMap uomMatrixSaveOrEdit(
    ModelMap model,
    @RequestParam("parentId") String parentId
){
    model.addAttribute("attributeValues",parentId);
    return model;
}

and here is my Java REST client:

public void post(){
    MultiValueMap<String, String> params = new LinkedMultiValueMap<String, String>();
    params.add("parentId", "parentId");
    String result = rest.postForObject( url, params, String.class) ;
    System.out.println(result);
}

This works for me; I get a JSON string from the server side.

My question is: how can I specify the Accept: header (e.g. application/json,application/xml, ... ) and request method (e.g. GET,POST, ... ) when I use RestTemplate?

Answer 1

If, like me, you struggled to find an example that uses headers with basic authentication and the rest template exchange API, this is what I finally worked out...

private HttpHeaders createHttpHeaders(String user, String password)
{
    String notEncoded = user + ":" + password;
    String encodedAuth = Base64.getEncoder().encodeToString(notEncoded.getBytes());
    HttpHeaders headers = new HttpHeaders();
    headers.setContentType(MediaType.APPLICATION_JSON);
    headers.add("Authorization", "Basic " + encodedAuth);
    return headers;
}

private void doYourThing() 
{
    String theUrl = "http://blah.blah.com:8080/rest/api/blah";
    RestTemplate restTemplate = new RestTemplate();
    try {
        HttpHeaders headers = createHttpHeaders("fred","1234");
        HttpEntity<String> entity = new HttpEntity<String>("parameters", headers);
        ResponseEntity<String> response = restTemplate.exchange(theUrl, HttpMethod.GET, entity, String.class);
        System.out.println("Result - status ("+ response.getStatusCode() + ") has body: " + response.hasBody());
    }
    catch (Exception eek) {
        System.out.println("** Exception: "+ eek.getMessage());
    }
}

Answer 2

Code : calling rest api using template

1)

       RestTemplate restTemplate = new RestTemplate();
        // Add the Jackson message converter
        restTemplate.getMessageConverters().add(new 
           MappingJackson2HttpMessageConverter());

        HttpHeaders headers = new HttpHeaders();
        headers.setContentType(MediaType.APPLICATION_JSON);
        headers.set("Authorization", "Basic XXXXXXXXXXXXXXXX=");
        HttpEntity<String> entity = new HttpEntity<String>("parameters", headers);

        restTemplate.getInterceptors().add(new BasicAuthorizationInterceptor(USERID, PWORD));

        String requestJson = getRequetJson(Code, emailAddr, firstName, lastName);
        //
        response = restTemplate.postForObject(URL, requestJson, MYObject.class);

or

2)

    RestTemplate restTemplate = new RestTemplate();
    String requestJson = getRequetJson(code, emil, name, lastName);

    //
    HttpHeaders headers = new HttpHeaders();
    String userPass = USERID + ":" + PWORD;
    String authHeaderValue = "Basic " + Base64.getEncoder().encodeToString(userPass.getBytes());
    headers.set(HttpHeaders.AUTHORIZATION, authHeaderValue);
    headers.setContentType(MediaType.APPLICATION_JSON);
    headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));
    HttpEntity<String> request = new HttpEntity<String>(requestJson, headers);
    //
    ResponseEntity<MyObject> responseEntity =this.restTemplate.exchange(URI, HttpMethod.POST, request, MyObject.class);

    responseEntity.getBody()

Method creating json object

    private String getRequetJson(String Code, String emailAddr, String firstName, String lastName) {
        ObjectMapper mapper = new ObjectMapper();
        JsonNode rootNode = mapper.createObjectNode();

        ((ObjectNode) rootNode).put("code", Code);
        ((ObjectNode) rootNode).put("email", emailAdd);
        ((ObjectNode) rootNode).put("firstName", firstname);
        ((ObjectNode) rootNode).put("lastName", lastname);

        String jsonString = null;
        try {
            jsonString = mapper.writerWithDefaultPrettyPrinter().writeValueAsString(rootNode);
        } catch (JsonProcessingException e) {

            e.printStackTrace();
        }
        return jsonString;

    }

Answer 3

You could set an interceptor "ClientHttpRequestInterceptor" in your RestTemplate to avoid setting the header every time you send a request.

public class HeaderRequestInterceptor implements ClientHttpRequestInterceptor {

        private final String headerName;

        private final String headerValue;

        public HeaderRequestInterceptor(String headerName, String headerValue) {
            this.headerName = headerName;
            this.headerValue = headerValue;
        }

        @Override
        public ClientHttpResponse intercept(HttpRequest request, byte[] body, ClientHttpRequestExecution execution) throws IOException {
            request.getHeaders().set(headerName, headerValue);
            return execution.execute(request, body);
        }
    }

Then

List<ClientHttpRequestInterceptor> interceptors = new ArrayList<ClientHttpRequestInterceptor>();
interceptors.add(new HeaderRequestInterceptor("Accept", MediaType.APPLICATION_JSON_VALUE));

RestTemplate restTemplate = new RestTemplate();
restTemplate.setInterceptors(interceptors);

Answer 4

Here is a simple answer. Hope it helps someone.

import org.springframework.boot.devtools.remote.client.HttpHeaderInterceptor;
import org.springframework.http.MediaType;
import org.springframework.http.client.ClientHttpRequestInterceptor;
import org.springframework.web.client.RestTemplate;


public String post(SomeRequest someRequest) {
    // create a list the headers 
    List<ClientHttpRequestInterceptor> interceptors = new ArrayList<>();
    interceptors.add(new HttpHeaderInterceptor("Accept", MediaType.APPLICATION_JSON_VALUE));
    interceptors.add(new HttpHeaderInterceptor("ContentType", MediaType.APPLICATION_JSON_VALUE));
    interceptors.add(new HttpHeaderInterceptor("username", "user123"));
    interceptors.add(new HttpHeaderInterceptor("customHeader1", "c1"));
    interceptors.add(new HttpHeaderInterceptor("customHeader2", "c2"));
    // initialize RestTemplate
    RestTemplate restTemplate = new RestTemplate();
    // set header interceptors here
    restTemplate.setInterceptors(interceptors);
    // post the request. The response should be JSON string
    String response = restTemplate.postForObject(Url, someRequest, String.class);
    return response;
}

Answer 5

I suggest using one of the exchange methods that accepts an HttpEntity for which you can also set the HttpHeaders. (You can also specify the HTTP method you want to use.)

For example,

RestTemplate restTemplate = new RestTemplate();
HttpHeaders headers = new HttpHeaders();
headers.setAccept(Collections.singletonList(MediaType.APPLICATION_JSON));

HttpEntity<String> entity = new HttpEntity<>("parameters", headers);

restTemplate.exchange(url, HttpMethod.POST, entity, String.class);

I prefer this solution because it's strongly typed, ie. exchange expects an HttpEntity.

However, you can also pass that HttpEntity as a request argument to postForObject.

HttpEntity<String> entity = new HttpEntity<>("parameters", headers);
restTemplate.postForObject(url, entity, String.class); 

This is mentioned in the RestTemplate#postForObject Javadoc.

The request parameter can be a HttpEntity in order to add additional HTTP headers to the request.