Collectives™ on Stack Overflow

Find centralized, trusted content and collaborate around the technologies you use most.

Learn more about Collectives

Teams

Q&A for work

Connect and share knowledge within a single location that is structured and easy to search.

Learn more about Teams final HttpClient httpClient = new HttpClient(); final PostMethod postMethod = new PostMethod(url); postMethod.addRequestHeader("Content-Type", "application/json"); postMethod.addParameters(new NameValuePair[]{ new NameValuePair("name", "value) httpClient.executeMethod(httpMethod); postMethod.getResponseBodyAsStream(); postMethod.releaseConnection();

It keeps coming back with a 500. The service provider says I need to send JSON. How is that done with Apache HttpClient 3.1+?

Your NameValuePair just adds a request parameter, you're not sending any JSON in your code. What JSON structure does the service expect to receive, what's your data to send? You're looking for postMethod.setRequestEntity() with a StringRequestEntity that contains your JSON. – Philipp Reichart Aug 21, 2012 at 16:51

Apache HttpClient doesn't know anything about JSON, so you'll need to construct your JSON separately. To do so, I recommend checking out the simple JSON-java library from json.org . (If "JSON-java" doesn't suit you, json.org has a big list of libraries available in different languages.)

Once you've generated your JSON, you can use something like the code below to POST it

StringRequestEntity requestEntity = new StringRequestEntity(
    JSON_STRING,
    "application/json",
    "UTF-8");
PostMethod postMethod = new PostMethod("http://example.com/action");
postMethod.setRequestEntity(requestEntity);
int statusCode = httpClient.executeMethod(postMethod);
Note - The above answer, as asked for in the question, applies to Apache HttpClient 3.1. However, to help anyone looking for an implementation against the latest Apache client:
StringEntity requestEntity = new StringEntity(
    JSON_STRING,
    ContentType.APPLICATION_JSON);
HttpPost postMethod = new HttpPost("http://example.com/action");
postMethod.setEntity(requestEntity);
HttpResponse rawResponse = httpclient.execute(postMethod);
                Always wanted to know if a parameter can be added to POSTMethod and at the same time set a RequestEntity to it? I know it sounds illogical, but just curious.
– asgs
                Mar 8, 2013 at 21:29
For Apache HttpClient 4.5 or newer version:
    CloseableHttpClient httpclient = HttpClients.createDefault();
    HttpPost httpPost = new HttpPost("http://targethost/login");
    String JSON_STRING="";
    HttpEntity stringEntity = new StringEntity(JSON_STRING,ContentType.APPLICATION_JSON);
    httpPost.setEntity(stringEntity);
    CloseableHttpResponse response2 = httpclient.execute(httpPost);
Note:
1 in order to make the code compile, both httpclient package and httpcore package should be imported.
2 try-catch block has been ommitted.
Reference:
appache official guide
  
the Commons HttpClient project is now end of life, and is no longer
  being developed. It has been replaced by the Apache HttpComponents
  project in its HttpClient and HttpCore modules
As mentioned in the excellent answer by janoside, you need to construct the JSON string and set it as a StringEntity.
To construct the JSON string, you can use any library or method you are comfortable with. Jackson library is one easy example:
import com.fasterxml.jackson.databind.ObjectMapper;
import com.fasterxml.jackson.databind.node.ObjectNode;
import org.apache.http.entity.ContentType;
import org.apache.http.entity.StringEntity;
ObjectMapper mapper = new ObjectMapper();
ObjectNode node = mapper.createObjectNode();
node.put("name", "value"); // repeat as needed
String JSON_STRING = node.toString();
postMethod.setEntity(new StringEntity(JSON_STRING, ContentType.APPLICATION_JSON));
I use JACKSON library to convert object to JSON and set the request body like below. Here is full example.
try (CloseableHttpClient httpclient = HttpClients.createDefault()) {
    HttpPost httpPost = new HttpPost("https://jsonplaceholder.typicode.com/posts");
    Post post = new Post("foo", "bar", 1);
    ObjectWriter ow = new ObjectMapper().writer();
    String strJson = ow.writeValueAsString(post);
    System.out.println(strJson);
    StringEntity strEntity = new StringEntity(strJson, ContentType.APPLICATION_JSON);
    httpPost.setEntity(strEntity);
    httpPost.setHeader("Content-type", "application/json");
    try (CloseableHttpResponse response = httpclient.execute(httpPost)) {
        System.out.println(response.getCode() + " " + response.getReasonPhrase());
        HttpEntity entity = response.getEntity();
        String result = EntityUtils.toString(entity);
        System.out.println(result);
        EntityUtils.consume(entity);
    } catch (ParseException e) {
        e.printStackTrace();
} catch (IOException e) {
    System.out.println(e.getMessage());
        
Thanks for contributing an answer to Stack Overflow!
Please be sure to answer the question. Provide details and share your research!
But avoid …
Asking for help, clarification, or responding to other answers.
Making statements based on opinion; back them up with references or personal experience.
To learn more, see our tips on writing great answers.