How to send a Java POST request

Question

I am completely lost on how to send a POST request in Java. I understand how to do in Python with the request module, but no luck with Java. So, I was wondering if anyone could give me a clear example of how this is done via logging into a webpage such as instagram.com. I appreciate all responses. Thanks in advance.

You've internet access, try Google – Abhijit Sarkar Mar 31 '18 at 23:23 — Abhijit Sarkar, Mar 31 '18 at 23:23

score 3 · Answer 1 · answered Mar 31 '18 at 23:11

if you do not want to use extra library，you can try HttpURLConnection:

public static String doPost(String url, String postData) {
    PrintWriter out = null;
    BufferedReader in = null;
    String result = "";
    try {
        URL realUrl = new URL(url);
        // build connection
        URLConnection conn = realUrl.openConnection();
        // set request properties
        conn.setRequestProperty("accept", "*/*");
        conn.setRequestProperty("connection", "Keep-Alive");
        conn.setRequestProperty("user-agent", "Mozilla/4.0 (compatible; MSIE 6.0; Windows NT 5.1; SV1)");
        // enable output and input
        conn.setDoOutput(true);
        conn.setDoInput(true);
        out = new PrintWriter(conn.getOutputStream());
        // send POST DATA
        out.print(postData);
        out.flush();
        in = new BufferedReader(new InputStreamReader(conn.getInputStream()));
        String line;
        while ((line = in.readLine()) != null) {
            result += "/n" + line;
        }
    } catch (Exception e) {
        e.printStackTrace();
    }
    finally {
        try {
            if (out != null) {
                out.close();
            }
            if (in != null) {
                in.close();
            }
        } catch (IOException ex) {
            ex.printStackTrace();
        }
    }
    return result;
}

I see the postData parameter, but how would I go about sending the info per say if the POST paramters for the request are "username" : "someUsername" and "password" : "somePassword" — Kyle, Mar 31 '18 at 23:16
just like this: String postData = URLEncoder.encode("key1", "UTF-8") + "=" + URLEncoder.encode("value1", "UTF-8"); postData += "&" + URLEncoder.encode("key2", "UTF-8") + "=" + URLEncoder.encode("value2", "UTF-8"); — Lyn, Apr 01 '18 at 11:54

score 2 · Answer 2 · answered Mar 31 '18 at 23:08

2

You can use Spring Web RestTemplate:

new RestTemplate().postForObject(url, requestObject, responseType);

answered Mar 31 '18 at 23:08

Svichkarev Anatoly

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1

Spring RT for someone who has no clue how to make a simple POST request? It's like saying a 4th grade student could get better in math by working a binomial theorem – Abhijit Sarkar Mar 31 '18 at 23:22

score 1 · Answer 3 · answered Mar 31 '18 at 22:58

you can use OkHttp

https://github.com/square/okhttp

public static final MediaType JSON
    = MediaType.parse("application/json; charset=utf-8");

OkHttpClient client = new OkHttpClient();

String post(String url, String json) throws IOException {
  RequestBody body = RequestBody.create(JSON, json);
  Request request = new Request.Builder()
      .url(url)
      .post(body)
      .build();
  Response response = client.newCall(request).execute();
  return response.body().string();
}

How to send a Java POST request

3 Answers3