How to Send HTTP POST Requests in Java?

Sending HTTP POST Request In Java

To transmit data to a server-side script, such as "page.php," that accepts POST requests, follow these steps:

Request Initialization:

Instantiate a URL object and open a connection:

URL aaa = new URL("http://www.example.com/page.php");
URLConnection ccc = aaa.openConnection();

POST Setup:

Configure the connection to allow POST data submission:

ccc.setDoOutput(true);
ccc.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");

Query Parameter Encoding:

Convert request parameters (e.g., id=10) into an encoded query string:

String data = "id=" + URLEncoder.encode("10", "UTF-8");

Data Transmission:

Write the data to the connection's output stream:

OutputStreamWriter wr = new OutputStreamWriter(ccc.getOutputStream());
wr.write(data);
wr.flush();

Response Handling:

Obtain and process the server's response:

BufferedReader br = new BufferedReader(new InputStreamReader(ccc.getInputStream()));
String response = br.readLine();

Updated Answer:

For Java programmers using Apache HTTP Components, the latest method involves HttpClients and HttpPost. Parameters are passed as a NameValuePair list, encoded into a UrlEncodedFormEntity, and then submitted to the server:

HttpClient httpclient = HttpClients.createDefault();
HttpPost httppost = new HttpPost("http://www.a-domain.example/foo/");

List<NameValuePair> params = new ArrayList<>(2);
params.add(new BasicNameValuePair("param-1", "12345"));
params.add(new BasicNameValuePair("param-2", "Hello!"));
httppost.setEntity(new UrlEncodedFormEntity(params, "UTF-8"));

HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();

if (entity != null) {
    try (InputStream instream = entity.getContent()) {
        // Process the response here.
    }
}

For more information, consult Apache HTTP Components' documentation.

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