java如何实现HTTP传输

在 Java 中实现 HTTP 传输（发送和接收 HTTP 请求），常见方式有几种，从原生 API到第三方库都有。下面按从简单到常用的方式给你介绍。

一、Java 11+ 原生方式（推荐，无需依赖）

1️⃣ 使用 java.net.http.HttpClient

适合：Java 11 及以上

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;

public class HttpExample {
    public static void main(String[] args) throws Exception {
        HttpClient client = HttpClient.newHttpClient();

        HttpRequest request = HttpRequest.newBuilder()
                .uri(URI.create("https://example.com"))
                .GET()
                .build();

        HttpResponse<String> response =
                client.send(request, HttpResponse.BodyHandlers.ofString());

        System.out.println(response.statusCode());
        System.out.println(response.body());
    }
}

✅ 支持：

• GET / POST / PUT / DELETE
• 同步 & 异步
• HTTPS
• 请求头、超时、Body

二、传统方式（Java 8 及以下）

2️⃣ 使用 HttpURLConnection

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

public class HttpURLExample {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://example.com");
        HttpURLConnection connection = (HttpURLConnection) url.openConnection();

        connection.setRequestMethod("GET");

        BufferedReader reader = new BufferedReader(
                new InputStreamReader(connection.getInputStream()));

        String line;
        while ((line = reader.readLine()) != null) {
            System.out.println(line);
        }
        reader.close();
    }
}

⚠️ 缺点：

• API 老旧
• 代码繁琐
• 不支持异步

三、Post 请求示例（HttpClient）

HttpRequest request = HttpRequest.newBuilder()
        .uri(URI.create("https://example.com/api"))
        .header("Content-Type", "application/json")
        .POST(HttpRequest.BodyPublishers.ofString(
                "{\"name\":\"tom\"}"))
        .build();

四、第三方库（生产环境常用）

3️⃣ Apache HttpClient

<dependency>
  <groupId>org.apache.httpcomponents.client5</groupId>
  <artifactId>httpclient5</artifactId>
</dependency>

CloseableHttpClient client = HttpClients.createDefault();
HttpGet get = new HttpGet("https://example.com");
CloseableHttpResponse response = client.execute(get);

✅ 功能强、稳定，适合复杂场景

4️⃣ OkHttp（Android / 后端都常用）

OkHttpClient client = new OkHttpClient();

Request request = new Request.Builder()
        .url("https://example.com")
        .build();

Response response = client.newCall(request).execute();

5️⃣ Spring RestTemplate / WebClient

Spring 项目推荐

RestTemplate restTemplate = new RestTemplate();
String result = restTemplate.getForObject(
        "https://example.com", String.class);

五、如何选择？

如果你有具体需求（如：上传文件、HTTPS、超时、代理、异步、JSON 传输），可以告诉我，我可以给你完整示例。