java HTTP客户端怎么写

在 Java 里写 HTTP 客户端有多种方式，下面按常见程度和现代程度给你几个最实用的写法示例。

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

不需要额外依赖，官方标准

1️⃣ GET 请求

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

public class HttpDemo {
    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 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\"}"
        ))
        .build();

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

3️⃣ 异步请求（非阻塞）

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

二、Apache HttpClient（老牌、功能强）

Maven 依赖

<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://example.com");

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

✅ 适合：复杂配置、连接池、重试、代理

三、Spring RestTemplate（Spring 项目常用）

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

⚠️ Spring 官方更推荐 WebClient

四、Spring WebClient（响应式 ✅ 推荐新项目）

WebClient client = WebClient.create();

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

五、怎么选？

如果你告诉我：

• Java 版本
• 是否 Spring
• 同步还是异步
• 是否要连接池 / 超时 / 代理

我可以直接给你可复制的完整代码。