Sending HTTP POST Request In Java

java

http-client

error-handling

post-request

byAlex Kataev·Aug 17, 2024

Perform an HTTP POST request swiftly in Java with HttpURLConnection. Follow these steps:

Define URL for the endpoint.
Setup HttpURLConnection, select "POST".
Allow output with setDoOutput(true).
Stream POST data using OutputStream.
Fetch response using InputStreamReader.

Here is a simple example:

URL url = new URL("http://www.example.com/api/submit");
HttpURLConnection con = (HttpURLConnection) url.openConnection();
con.setRequestMethod("POST");
con.setDoOutput(true);

// "name=John&age=30", immortal payload, isn't John a lucky guy!?
String postData = "name=John&age=30";
try(OutputStream os = con.getOutputStream()) {
    os.write(postData.getBytes(StandardCharsets.UTF_8));
}

StringBuilder response = new StringBuilder();
try(InputStream responseStream = con.getInputStream()) {
    BufferedReader reader = new BufferedReader(new InputStreamReader(responseStream));
    String line;
    while ((line = reader.readLine()) != null) {
        response.append(line);
    }
}

System.out.println(response);

Always remember: Code that doesn't catch is almost as bad as fishing with no bait!. Error handling and resource management, like try-with-resources, are super crucial.

Level Up: Using Apache HttpClient

If your POST request demands more robust handling, then prepare yourself for the incredible Apache HttpClient library. Out of the box, it offers enhanced features and superior configuration standards.

Getting started: Initialize `HttpClient` and `HttpPost`

// Mission control, we're ready for takeoff!
CloseableHttpClient httpClient = HttpClients.createDefault();
HttpPost httpPost = new HttpPost("http://www.example.com/api/submit");

Polishing Sparklers: Adding Parameters

We use NameValuePair and UrlEncodedFormEntity for adding request parameters:

// Can't choose where to go if we don't have any directions!
List<NameValuePair> params = new ArrayList<>();
params.add(new BasicNameValuePair("name", "John"));
params.add(new BasicNameValuePair("age", "30"));
httpPost.setEntity(new UrlEncodedFormEntity(params, StandardCharsets.UTF_8));

Blast-off and Arrival: Sending and Receiving Data

Let's send the request and handle the response:

// Brace for response!
CloseableHttpResponse response = httpClient.execute(httpPost);
try {
    // Houston, we've got a status!
    System.out.println("Response Code : " + response.getStatusLine().getStatusCode());
    String responseString = EntityUtils.toString(response.getEntity(), "UTF-8");
    System.out.println("Response String : " + responseString);
} finally {
    // Back to Earth!
    response.close();
}

Remind yourself to set suitable headers, ace your exceptions, and close the resources after their mission.

When to call in the heroes: use cases

When you're filing form-like data
Uploading files with multipart POST
When you need to pass special headers and authentication tokens

Power Up: Error Handling and Resource Management

Always apply "Safety First!" principle—it's your ticket to smooth coding. Wrap requests in try-catch blocks or use try-with-resources to ensure orderly resource management, even when errors decide to throw a party!

Example: try-with-resources in action

// Never forget your safety goggles!
try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
    HttpPost httpPost = new HttpPost("http://www.example.com/api/submit");
    // ... additional setup
    try (CloseableHttpResponse response = httpClient.execute(httpPost)) {
        // Enjoy handling response, it's a party!
    }
} catch (IOException e) {
    e.printStackTrace(); // Remember, an error logged is an error half-solved!
}

Pitfalls to Monogram on your Fridge

Forgetting the SSL/TLS validation errors
Not defining timeout values
Ignoring the response because it asked for extra homework

Hook, Line, and Sinker: Streamlining Repetitive Tasks

Utilize HttpRequest Fluent API to make your HTTP requests just like a country song—simple and enjoyable!

// We're on a roll here, shooting stars can't make this up!
String result = Request.Post("http://www.example.com/api/submit")
                       .bodyForm(Form.form().add("name", "John").add("age", "30").build())
                       .execute().returnContent().asString();