HTTP POST using JSON in Java

Question

I would like to make a simple HTTP POST using JSON in Java.

Let's say the URL is www.site.com

and it takes in the value {"name":"myname","age":"20"} labeled as 'details' for example.

How would I go about creating the syntax for the POST?

I also can't seem to find a POST method in the JSON Javadocs.

Answer 1

Here is what you need to do:

1. Get the Apache HttpClient, this would enable you to make the required request
2. Create an HttpPost request with it and add the header "application/x-www-form-urlencoded"
3. Create a StringEntity that you will pass JSON to it
4. Execute the call

The code roughly looks like (you will still need to debug it and make it work)

//Deprecated
//HttpClient httpClient = new DefaultHttpClient(); 

HttpClient httpClient = HttpClientBuilder.create().build(); //Use this instead 

try {

    HttpPost request = new HttpPost("http://yoururl");
    StringEntity params =new StringEntity("details={\"name\":\"myname\",\"age\":\"20\"} ");
    request.addHeader("content-type", "application/x-www-form-urlencoded");
    request.setEntity(params);
    HttpResponse response = httpClient.execute(request);

    //handle response here...

}catch (Exception ex) {

    //handle exception here

} finally {
    //Deprecated
    //httpClient.getConnectionManager().shutdown(); 
}

Answer 2

You can make use of Gson library to convert your java classes to JSON objects.

Create a pojo class for variables you want to send as per above Example

{"name":"myname","age":"20"}

becomes

class pojo1
{
   String name;
   String age;
   //generate setter and getters
}

once you set the variables in pojo1 class you can send that using the following code

String       postUrl       = "www.site.com";// put in your url
Gson         gson          = new Gson();
HttpClient   httpClient    = HttpClientBuilder.create().build();
HttpPost     post          = new HttpPost(postUrl);
StringEntity postingString = new StringEntity(gson.toJson(pojo1));//gson.tojson() converts your pojo to json
post.setEntity(postingString);
post.setHeader("Content-type", "application/json");
HttpResponse  response = httpClient.execute(post);

and these are the imports

import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.entity.StringEntity;
import org.apache.http.impl.client.HttpClientBuilder;

and for GSON

import com.google.gson.Gson;

Answer 3

I recomend http-request built on apache http api.

HttpRequest<String> httpRequest = HttpRequestBuilder.createPost(yourUri, String.class)
    .responseDeserializer(ResponseDeserializer.ignorableDeserializer()).build();

public void send(){
   ResponseHandler<String> responseHandler = httpRequest.execute("details", yourJsonData);

   int statusCode = responseHandler.getStatusCode();
   String responseContent = responseHandler.orElse(null); // returns Content from response. If content isn't present returns null. 
}

If you want send JSON as request body you can:

  ResponseHandler<String> responseHandler = httpRequest.executeWithBody(yourJsonData);

I higly recomend read documentation before use.

Answer 4

I found this question looking for solution about how to send post request from java client to Google Endpoints. Above answers, very likely correct, but not work in case of Google Endpoints.

Solution for Google Endpoints.

1. Request body must contains only JSON string, not name=value pair.

2. Content type header must be set to "application/json".

   post("http://localhost:8888/_ah/api/langapi/v1/createLanguage",
                      "{\"language\":\"russian\", \"description\":\"dsfsdfsdfsdfsd\"}");
   
   
   
   public static void post(String url, String param ) throws Exception{
     String charset = "UTF-8"; 
     URLConnection connection = new URL(url).openConnection();
     connection.setDoOutput(true); // Triggers POST.
     connection.setRequestProperty("Accept-Charset", charset);
     connection.setRequestProperty("Content-Type", "application/json;charset=" + charset);
   
     try (OutputStream output = connection.getOutputStream()) {
       output.write(param.getBytes(charset));
     }
   
     InputStream response = connection.getInputStream();
   }
   

   It sure can be done using HttpClient as well.

Answer 5

Try this code:

HttpClient httpClient = new DefaultHttpClient();

try {
    HttpPost request = new HttpPost("http://yoururl");
    StringEntity params =new StringEntity("details={\"name\":\"myname\",\"age\":\"20\"} ");
    request.addHeader("content-type", "application/json");
    request.addHeader("Accept","application/json");
    request.setEntity(params);
    HttpResponse response = httpClient.execute(request);

    // handle response here...
}catch (Exception ex) {
    // handle exception here
} finally {
    httpClient.getConnectionManager().shutdown();
}

Answer 6

protected void sendJson(final String play, final String prop) {
     Thread t = new Thread() {
     public void run() {
        Looper.prepare(); //For Preparing Message Pool for the childThread
        HttpClient client = new DefaultHttpClient();
        HttpConnectionParams.setConnectionTimeout(client.getParams(), 1000); //Timeout Limit
        HttpResponse response;
        JSONObject json = new JSONObject();

            try {
                HttpPost post = new HttpPost("http://192.168.0.44:80");
                json.put("play", play);
                json.put("Properties", prop);
                StringEntity se = new StringEntity(json.toString());
                se.setContentType(new BasicHeader(HTTP.CONTENT_TYPE, "application/json"));
                post.setEntity(se);
                response = client.execute(post);

                /*Checking response */
                if (response != null) {
                    InputStream in = response.getEntity().getContent(); //Get the data in the entity
                }

            } catch (Exception e) {
                e.printStackTrace();
                showMessage("Error", "Cannot Estabilish Connection");
            }

            Looper.loop(); //Loop in the message queue
        }
    };
    t.start();
}