怎样用java处理HTTP

在 Java 中处理 HTTP 请求和响应，常见方式有以下几种，从原生到现代框架都有。下面按“从简单到常用”给你一个清晰路线。

一、使用 Java 原生 HttpURLConnection（不依赖第三方库）

适合：简单请求、学习原理、受限环境

1️⃣ 发送 GET 请求

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

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

        conn.setRequestMethod("GET");
        conn.setConnectTimeout(5000);
        conn.setReadTimeout(5000);

        int code = conn.getResponseCode();
        System.out.println("响应码：" + code);

        try (BufferedReader reader =
                     new BufferedReader(new InputStreamReader(conn.getInputStream()))) {
            String line;
            while ((line = reader.readLine()) != null) {
                System.out.println(line);
            }
        }
    }
}

2️⃣ 发送 POST 请求（JSON）

import java.io.OutputStream;
import java.net.HttpURLConnection;
import java.net.URL;

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

        conn.setRequestMethod("POST");
        conn.setDoOutput(true);
        conn.setRequestProperty("Content-Type", "application/json");

        String json = "{\"username\":\"admin\",\"password\":\"123\"}";

        try (OutputStream os = conn.getOutputStream()) {
            os.write(json.getBytes());
        }

        System.out.println("响应码：" + conn.getResponseCode());
    }
}

二、使用 Java 11+ java.net.http.HttpClient（推荐 ✅）

官方现代 HTTP 客户端，支持：

• HTTP/1.1 和 HTTP/2
• 异步
• 流式处理

1️⃣ GET 请求

import java.net.URI;
import java.net.http.*;

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

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

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

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

2️⃣ POST JSON

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

3️⃣ 异步请求

client.sendAsync(request, HttpResponse.BodyHandlers.ofString())
      .thenApply(HttpResponse::body)
      .thenAccept(System.out::println);

三、使用第三方库（实际项目最常用）

✅ 1. Apache HttpClient

适合：复杂配置、老项目

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

✅ 2. OkHttp（Square，轻量好用）

OkHttpClient client = new OkHttpClient();

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

Response response = client.newCall(request).execute();
System.out.println(response.body().string());

✅ 3. Spring 的 RestTemplate / WebClient

Spring 项目首选

RestTemplate（同步）

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

WebClient（响应式、推荐新项目）

WebClient.create()
        .get()
        .uri("https://api.example.com/data")
        .retrieve()
        .bodyToMono(String.class)
        .subscribe(System.out::println);

四、在 Java 中“接收”HTTP 请求（做服务端）

1️⃣ Spring Boot（最常用）

@RestController
public class DemoController {

    @GetMapping("/hello")
    public String hello() {
        return "Hello HTTP";
    }
}

2️⃣ 原生 Servlet

@WebServlet("/demo")
public class DemoServlet extends HttpServlet {
    protected void doGet(HttpServletRequest req, HttpServletResponse resp) {
        // 处理 HTTP 请求
    }
}

五、怎么选？

如果你愿意，我可以：

• 给你一个完整 HTTP 工具类
• 教你如何处理 HTTPS / 证书
• 写文件上传 / 下载
• 用 Spring Boot 写 HTTP 接口

你现在是 客户端调用 还是 写服务端接口？