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

User · Answer

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));

User · Answer

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official guide     the Commons HttpClient project is now end of life  and is no longer   being developed  It has been replaced by the Apache HttpComponents   project in its HttpClient and HttpCore modules

User · Answer

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

[java] How to POST JSON request using Apache HttpClient?

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