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java如何发送请求

2026-03-23 16:49:46Java

发送HTTP请求的方法

在Java中发送HTTP请求可以通过多种方式实现，以下是几种常见的方法：

使用HttpURLConnection

HttpURLConnection是Java标准库中用于发送HTTP请求的类，适用于简单的请求场景。

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

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

        int responseCode = con.getResponseCode();
        BufferedReader in = new BufferedReader(new InputStreamReader(con.getInputStream()));
        String inputLine;
        StringBuilder response = new StringBuilder();

        while ((inputLine = in.readLine()) != null) {
            response.append(inputLine);
        }
        in.close();

        System.out.println(response.toString());
    }
}

使用Apache HttpClient

Apache HttpClient是一个功能更丰富的第三方库，适合复杂的HTTP请求场景。

import org.apache.http.client.methods.CloseableHttpResponse;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.CloseableHttpClient;
import org.apache.http.impl.client.HttpClients;
import org.apache.http.util.EntityUtils;

public class HttpClientExample {
    public static void main(String[] args) throws Exception {
        CloseableHttpClient httpClient = HttpClients.createDefault();
        HttpGet request = new HttpGet("https://example.com/api");

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

        response.close();
        httpClient.close();
    }
}

使用OkHttp

OkHttp是Square公司开发的现代HTTP客户端，性能优异且易于使用。

import okhttp3.OkHttpClient;
import okhttp3.Request;
import okhttp3.Response;

public class OkHttpExample {
    public static void main(String[] args) throws Exception {
        OkHttpClient client = new OkHttpClient();
        Request request = new Request.Builder()
            .url("https://example.com/api")
            .build();

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

使用Spring RestTemplate

对于Spring项目，可以使用RestTemplate简化HTTP请求的发送。

import org.springframework.web.client.RestTemplate;

public class RestTemplateExample {
    public static void main(String[] args) {
        RestTemplate restTemplate = new RestTemplate();
        String result = restTemplate.getForObject("https://example.com/api", String.class);
        System.out.println(result);
    }
}

发送POST请求示例

以下是一个使用HttpURLConnection发送POST请求的示例：

java如何发送请求

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

public class PostExample {
    public static void main(String[] args) throws Exception {
        URL url = new URL("https://example.com/api");
        HttpURLConnection con = (HttpURLConnection) url.openConnection();
        con.setRequestMethod("POST");
        con.setRequestProperty("Content-Type", "application/json");
        con.setDoOutput(true);

        String jsonInputString = "{\"name\":\"John\", \"age\":30}";
        try(OutputStream os = con.getOutputStream()) {
            byte[] input = jsonInputString.getBytes("utf-8");
            os.write(input, 0, input.length);
        }

        int responseCode = con.getResponseCode();
        System.out.println("Response Code: " + responseCode);
    }
}

以上方法各有优缺点，选择哪种取决于项目需求和开发环境。HttpURLConnection适合简单需求且无需额外依赖的场景；Apache HttpClient和OkHttp功能更全面；Spring RestTemplate则适合Spring项目。

标签: java