java HTTP请求如何发送

在 Java 中发送 HTTP 请求有多种方式，下面按常见程度从简单到灵活给你介绍几种主流做法，并附带示例。

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

优点：标准库、支持同步/异步、HTTP/2
适用：Java 11 及以上

1️⃣ GET 请求

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

public class HttpDemo {
    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 请求（JSON）

HttpRequest request = HttpRequest.newBuilder()
        .uri(URI.create("https://api.example.com/login"))
        .header("Content-Type", "application/json")
        .POST(HttpRequest.BodyPublishers.ofString(
                "{\"username\":\"admin\",\"password\":\"123\"}"))
        .build();

二、Apache HttpClient（企业常用 ⭐）

依赖（Maven）

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

GET 示例

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

CloseableHttpResponse response = client.execute(get);
String result = EntityUtils.toString(response.getEntity());
System.out.println(result);

POST JSON

HttpPost post = new HttpPost("https://api.example.com/login");
post.setHeader("Content-Type", "application/json");
post.setEntity(new StringEntity("{\"name\":\"tom\"}"));

client.execute(post);

三、Spring 项目：RestTemplate（简单 ⚡）

适用：Spring / Spring Boot

@RestController
public class Demo {
    @Autowired
    RestTemplate restTemplate;

    public void test() {
        String result = restTemplate.getForObject(
                "https://api.example.com/data", String.class);
    }
}

Spring 官方更推荐 WebClient（响应式）

四、Spring 5+：WebClient（异步 ✅）

WebClient client = WebClient.create();

String result = client.get()
        .uri("https://api.example.com/data")
        .retrieve()
        .bodyToMono(String.class)
        .block();

五、URLConnection（老方式 ❌）

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

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

六、如何选择？

如果你愿意，可以告诉我：

• Java 版本
• 是否 Spring 项目
• 请求类型（GET / POST / 文件上传）

我可以直接帮你写完整可用代码。