Question

I’m using Apache HttpComponents Client to POST to a server that returns JSON. The problem is that if the server returns a 400 error, I seem to have no way of telling what the error was from Java (had to resort to a packet sniffer so far – ridiculous). Here is the code:

HttpClient httpclient = new DefaultHttpClient();
params.add(new BasicNameValuePair("format", "json"));
params.add(new BasicNameValuePair("foo", bar));

HttpPost httppost = new HttpPost(uri);
// this is how you set the body of the POST request
httppost.setEntity(new UrlEncodedFormEntity(params, "UTF-8"));

String responseBody = "";
try {
    // Create a response handler
    ResponseHandler<String> responseHandler = new BasicResponseHandler();
    responseBody = httpclient.execute(httppost, responseHandler);
} catch(HttpResponseException e) {
    String error = "unknown error";
    if (e.getStatusCode() == 400) {
        // TODO responseBody and e.detailMessage are null here, 
        // even though packet sniffing may reveal a response like
        // Transfer-Encoding: chunked
        // Content-Type: application/json
        //
        // 42
        // {"error": "You do not have permissions for this operation."}
        error = new JSONObject(responseBody).getString("error");  // won't work
        }
    // e.getMessage() is ""
}

What am I doing wrong? There must be an easy way to get the message of a 400 error. This is elementary.

Answer 1

Why do you use BasicResponseHandler()? The handler is doing that for you. That handler is just an example and shouldn’t be used in real code.

You should either write your own handler or call execute without a handler.

For example,

        HttpResponse response = httpClient.execute(request);
        int statusCode = response.getStatusLine().getStatusCode();
        HttpEntity entity = response.getEntity();
        responseBody = entity.getContent();

        if (statusCode != 200) {
            // responseBody will have the error response
        }