How to send a POST request in Java?
Answer: Use HttpURLConnection to send a POST request, set the request method to POST and configure Content-Type, write JSON or form data through OutputStream, and then read the response. For example, submit {name: "John", age: 30} to https://httpbin.org/post to get the returned results. For complex requirements, the Apache HttpClient library can be used to implement more concise code.
To send a POST request in Java, you can use the built-in HttpURLConnection class from the java.net package. This approach doesn't require any external libraries and works well for basic HTTP communication.
1. Using HttpURLConnection
This is the standard way to make HTTP requests using core Java:
import java.io.*;
import java.net.HttpURLConnection;
import java.net.URL;
import java.nio.charset.StandardCharsets;
public class PostExample {
public static void main(String[] args) {
try {
URL url = new URL("https://httpbin.org/post");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();
// Set request method and headers
conn.setRequestMethod("POST");
conn.setDoOutput(true);
conn.setRequestProperty("Content-Type", "application/json; charset=UTF-8");
// Write JSON body
String jsonInput = "{\"name\": \"John\", \"age\": 30}";
try (OutputStream os = conn.getOutputStream()) {
byte[] input = jsonInput.getBytes(StandardCharsets.UTF_8);
os.write(input, 0, input.length);
}
//Read response
try (BufferedReader br = new BufferedReader(
new InputStreamReader(conn.getInputStream(), StandardCharsets.UTF_8))) {
StringBuilder response = new StringBuilder();
String responseLine;
while ((responseLine = br.readLine()) != null) {
response.append(responseLine.trim());
}
System.out.println(response.toString());
}
conn.disconnect();
} catch (IOException e) {
e.printStackTrace();
}
}
}
2. Handling Form Data (x-www-form-urlencoded)
If you're sending form data instead of JSON, format the body accordingly:
String formData = "username=john&password=secret";
conn.setRequestProperty("Content-Type", "application/x-www-form-urlencoded");
try (OutputStream os = conn.getOutputStream()) {
byte[] input = formData.getBytes(StandardCharsets.UTF_8);
os.write(input, 0, input.length);
}
3. Using Apache HttpClient (Third-party Option)
For more advanced features, consider using Apache HttpClient. Add this Maven dependency:
<dependency>
<groupid>org.apache.httpcomponents</groupid>
<artifactid>httpclient</artifactid>
<version>4.5.14</version>
</dependency>
Then send a POST request like this:
CloseableHttpClient client = HttpClients.createDefault();
HttpPost post = new HttpPost("https://httpbin.org/post");
//Add JSON body
StringEntity body = new StringEntity("{\"name\":\"John\"}", ContentType.APPLICATION_JSON);
post.setEntity(body);
try (CloseableHttpResponse response = client.execute(post)) {
HttpEntity responseEntity = response.getEntity();
if (responseEntity != null) {
System.out.println(EntityUtils.toString(responseEntity));
}
}
Basically just pick the method that fits your project's needs. HttpURLConnection is good for simple cases, while Apache HttpClient gives you more control and cleaner syntax.The above is the detailed content of How to send a POST request in Java?. For more information, please follow other related articles on the PHP Chinese website!
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