java如何发送HTTP

在 Java 中发送 HTTP 请求有多种方式，下面按常用程度和Java 版本给你介绍几种主流做法，并附上示例。

✅ 一、Java 11+（推荐）：java.net.http.HttpClient

这是 官方标准、最推荐 的方式，支持 HTTP/1.1 和 HTTP/2。

1️⃣ 发送 GET 请求

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());
    }
}

2️⃣ 发送 POST 请求（JSON）

HttpRequest request = HttpRequest.newBuilder()
        .uri(URI.create("https://example.com/api"))
        .header("Content-Type", "application/json")
        .POST(HttpRequest.BodyPublishers.ofString(
                "{\"name\":\"Tom\",\"age\":18}"))
        .build();

✅ 二、Java 8 及以前：HttpURLConnection

老项目常见，但 API 比较繁琐。

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

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

        conn.setRequestMethod("GET");

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

✅ 三、第三方库（更强大、更方便）

1️⃣ Apache HttpClient（企业常用）

<dependency>
  <groupId>org.apache.httpcomponents.client5</groupId>
  <artifactId>httpclient5</artifactId>
  <version>5.3</version>
</dependency>

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

2️⃣ OkHttp（Android / 高性能）

OkHttpClient client = new OkHttpClient();

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

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

✅ 四、如何选择？

✅ 五、常见需求示例

设置超时

HttpClient client = HttpClient.newBuilder()
        .connectTimeout(Duration.ofSeconds(5))
        .build();

异步请求

client.sendAsync(request, HttpResponse.BodyHandlers.ofString())
      .thenAccept(res -> System.out.println(res.body()));

如果你愿意，可以告诉我：

• ✅ Java 版本
• ✅ GET / POST / PUT / DELETE
• ✅ 是否需要 JSON / Header / 文件上传

我可以直接给你一段可直接用的代码。