How does Java network programming implement HTTP-based communication?

Java Network Programming: Implementing HTTP-based Communication

Introduction

HTTP (Hypertext Transport Protocol) is the basic protocol used in Web communications. In Java, we can use the HTTP client library to make HTTP requests to other servers and receive responses.

Using the HTTP Client library

The Java standard library provides the java.net.HttpURLConnection class, which can be used to send HTTP requests. We can use it through the following steps:

1. Create a HttpURLConnection object:

URL url = new URL("https://example.com");
HttpURLConnection conn = (HttpURLConnection) url.openConnection();

2. Configure request parameters:

// 設置請求方法 (GET或POST)
conn.setRequestMethod("GET");
// 设置请求头
conn.setRequestProperty("Content-Type", "application/json");

3. Send Request and get the response:

// 发送请求
conn.connect();
// 获取响应状态码
int responseCode = conn.getResponseCode();
// 获取响应主体（如果响应是成功代码）
if (responseCode == HttpURLConnection.HTTP_OK) {
    InputStream in = conn.getInputStream();
    // 处理响应主体
}

Practical case: Get the HTTP response

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;

public class HttpGetExample {
    public static void main(String[] args) throws IOException {
        // 创建 URL
        URL url = new URL("https://www.example.com");

        // 打开连接
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();

        // 发送 GET 请求
        connection.setRequestMethod("GET");
        connection.connect();

        // 获取响应状态码
        int responseCode = connection.getResponseCode();

        // 打印响应状态码
        System.out.println("响应状态码：" + responseCode);

        // 如果响应码是 200，则读取响应体
        if (responseCode == HttpURLConnection.HTTP_OK) {
            BufferedReader reader = new BufferedReader(new InputStreamReader(connection.getInputStream()));
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
            reader.close();
        }

        // 关闭连接
        connection.disconnect();
    }
}

In this example, we sent a GET request using HttpURLConnection Go to example.com, and print the response status code and response content.

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