Java API development practice: How to use HTTP protocol for data transmission?

Java API development practice: How to use HTTP protocol for data transmission?

HTTP (HyperText Transfer Protocol) is a protocol used to transfer files (such as HTML files, images, audio, videos, etc.). When developing web applications, you often need to use the HTTP protocol to communicate with the web server. Java provides a variety of methods to use the HTTP protocol for data transmission. This article will introduce how to use the Java API for HTTP data transmission.

1. HttpURLConnection class

HttpURLConnection is a built-in class in Java that is used to establish an HTTP connection between the client and the server. You can use this class for data transfer, such as sending data to the server via GET or POST methods.

The following is a sample code that uses the HttpURLConnection class to send a GET request to the server:

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
 
public class HttpURLConnectionExample {
    
    private static final String USER_AGENT = "Mozilla/5.0";
    
    public static void main(String[] args) throws Exception {
 
        String url = "http://www.example.com";
 
        URL obj = new URL(url);
        HttpURLConnection con = (HttpURLConnection) obj.openConnection();
 
        con.setRequestMethod("GET");
        con.setRequestProperty("User-Agent", USER_AGENT);
 
        int responseCode = con.getResponseCode();
        System.out.println("Response Code : " + responseCode);
 
        BufferedReader in = new BufferedReader(
                new InputStreamReader(con.getInputStream()));
        String inputLine;
        StringBuffer response = new StringBuffer();
 
        while ((inputLine = in.readLine()) != null) {
            response.append(inputLine);
        }
        in.close();
 
        System.out.println(response.toString());
 
    }
}

2. Apache HttpClient class library

Apache HttpClient is an open source Java HTTP client library can be used to send GET or POST requests to the web server, and supports advanced functions such as multiple authentication methods.

The following is a sample code that uses the Apache HttpClient class library to send a GET request:

import org.apache.http.HttpEntity;
import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;
 
public class ApacheHttpClientExample {
 
    public static void main(String[] args) throws Exception {
 
        CloseableHttpClient httpclient = HttpClients.createDefault();
        HttpGet httpget = new HttpGet("http://www.example.com");
 
        CloseableHttpResponse response = httpclient.execute(httpget);
        try {
            HttpEntity entity = response.getEntity();
            if (entity != null) {
                System.out.println(EntityUtils.toString(entity));
            }
        } finally {
            response.close();
        }
    }
}

3. OkHttp class library

OkHttp is developed by Square An efficient HTTP client library that is easy to use and has excellent performance. It is widely popular in Android development. OkHttp supports multiple HTTP request methods such as GET, POST, PUT, and DELETE.

The following is a sample code that uses the OkHttp class library to make a GET request:

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;
 
import java.io.IOException;
 
public class OkHttpExample {
 
    private final OkHttpClient httpClient = new OkHttpClient();
 
    public static void main(String[] args) throws IOException {
 
        OkHttpExample http = new OkHttpExample();
 
        System.out.println("Sending GET request...");
        String response = http.sendGet("http://www.example.com");
        System.out.println(response);
 
    }
 
    private String sendGet(String url) throws IOException {
 
        Request request = new Request.Builder()
                .url(url)
                .build();
 
        try (Response response = httpClient.newCall(request).execute()) {
 
            if (!response.isSuccessful()) throw new IOException("Unexpected code " + response);
 
            return response.body().string();
        }
 
    }
}

Summary:

For Java developers, it can be achieved using HttpURLConnection, Apache HttpClient or OkHttp HTTP data transmission, which method to choose can be decided according to specific needs and project characteristics. Using Java API can easily complete HTTP data transmission, which also brings better flexibility and scalability.

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