Get Json / Resonse body from Curl Post Request in Java-CodePudding

This is the method I have written which sends a POST request to send an Email. I am able to send the email and get the Response Code 200 Ok. But I don't know how to get the JSON Response and convert it into an Object. Can someone please tell me how to do this?

public void sendEmail() {
        try {
            URL url = new URL("https://mandrillapp.com/api/1.0/messages/send");

            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            httpURLConnection.setRequestProperty("Content-Type", "application/json");

            String data =
                    "{\"key\": \""   mailchimpApiKey   "\", "  
                            "\"message\": {"  
                            "\"from_email\": \"[email protected]\", "  
                            "\"subject\": \"Hello World\", "  
                            "\"text\": \"Welcome to Mailchimp Transactional!\", "  
                            "\"to\": [{ \"email\": \"[email protected]\", \"type\": \"to\" }]}}";

            byte[] out = data.getBytes(StandardCharsets.UTF_8);

            OutputStream stream = httpURLConnection.getOutputStream();
            stream.write(out);

            System.out.println(httpURLConnection.getResponseCode()   " "   httpURLConnection.getResponseMessage());

            httpURLConnection.disconnect();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

CodePudding user response：

A basic search reveals: https://www.baeldung.com/httpurlconnection-post#8-read-the-response-from-input-stream

try(BufferedReader br = new BufferedReader(
  new InputStreamReader(con.getInputStream(), "utf-8"))) {
    StringBuilder response = new StringBuilder();
    String responseLine = null;
    while ((responseLine = br.readLine()) != null) {
        response.append(responseLine.trim());
    }
    System.out.println(response.toString());
}

If the response is in JSON format, use any third-party JSON parsers such as Jackson library, Gson, or org.json to parse the response.

CodePudding user response：

You can get errorStream or inputStream based on the response code you receive and get the response from it. Below example creates a BufferedReader from the stream

BufferedReader br = null;
if (100 <= httpURLConnection.getResponseCode() && httpURLConnection.getResponseCode() <= 399) {
    br = new BufferedReader(new InputStreamReader(httpURLConnection.getInputStream()));
} else {
    br = new BufferedReader(new InputStreamReader(httpURLConnection.getErrorStream()));
}

You can then read from the br and store data based on your requirement. Below will store data into StringBuilder

StringBuilder data = new StringBuilder();
    String dataLine = null;
    while ((dataLine = br.readLine()) != null) {
        data.append(dataLine.trim());
    }
    System.out.println(data.toString());

Instead of printing as String you can also convert it into JSON by using JSON libraries. You may follow this guide

CodePudding user response：

In addition to the answer by @mdre

I use the org.json library to convert responses into JSON Objects. The following method does exactly this:

import org.json.JSONException;
import org.json.JSONObject;

    public static JSONObject convertResponseToJSONObject(String responseString) {
        try {
            JSONObject jsonObj = new JSONObject(responseString);
            return jsonObj;
        } catch (JSONException e) {
            System.err.println(
                "It is not possible to create a JSONObject from the input string, returning null. Exception:");
            e.printStackTrace();
        }
        return null;
    }

Note that the response only represents a JSON object if it starts with a {. If it starts with a [ the response represents a JSON array.