How to POST JSON request using Apache HttpClient?

Question

I have something like the following:

final String url = "http://example.com";

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
– Philipp Reichart, Commented Aug 21, 2012 at 16:51

janoside · Accepted Answer · 2016-07-25 19:38:31Z

216

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);

Edit

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);

edited Jul 25, 2016 at 19:38

answered Aug 21, 2012 at 17:36

janoside

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4 Comments

Mr Lou Over a year ago

How can append the json to the geturl?

asgs Over a year ago

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.

Alex Over a year ago

For those wondering, StringRequestEntity has been replaced by StringEntity.

Aviro Over a year ago

With later releases of HttpClient, PostMethod had been replaced by HttpPost.

ZhaoGang · Accepted Answer · 2018-10-26 07:51:30Z

36

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

edited Oct 26, 2018 at 7:51

answered Oct 25, 2018 at 1:39

ZhaoGang

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Comments

ADTC · Accepted Answer · 2018-03-20 01:02:33Z

13

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));

answered Mar 20, 2018 at 1:02

ADTC

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Comments

Supun Sandaruwan · Accepted Answer · 2022-01-29 02:33:36Z

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());
}

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