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+?

Answer 1

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);