标题：Java实现HTTP GET请求的三种常用方法详解
关键词：Java HTTP请求, GET请求, HttpURLConnection, HttpClient, OkHttp
描述：本文详细介绍Java中发送HTTP GET请求的三种主流实现方式，包含HttpURLConnection原生方法、Apache HttpClient工具库以及OkHttp第三方库的完整代码示例和最佳实践。

正文：

在Java开发中，HTTP请求是与外部服务交互的基础操作。本文将深入讲解三种主流的GET请求实现方案，帮助开发者根据项目需求选择最适合的技术方案。

一、原生HttpURLConnection方案

JDK自带的HttpURLConnection是Java最基础的HTTP客户端，无需额外依赖即可使用：

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

public class BasicGetRequest {
    public static void main(String[] args) throws Exception {
        String url = "https://api.example.com/data";
        URL obj = new URL(url);
        HttpURLConnection con = (HttpURLConnection) obj.openConnection();
        
        con.setRequestMethod("GET");
        con.setConnectTimeout(5000);
        con.setReadTimeout(5000);
        
        int responseCode = con.getResponseCode();
        System.out.println("响应状态码: " + responseCode);
        
        try (BufferedReader in = new BufferedReader(
                new InputStreamReader(con.getInputStream()))) {
            String inputLine;
            StringBuilder response = new StringBuilder();
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            System.out.println("响应内容: " + response);
        }
    }
}

该方法虽然代码量较大，但在简单场景下性能表现优秀。需要注意正确处理异常和资源释放，避免连接泄漏。

二、Apache HttpClient方案

Apache提供的HttpClient工具库功能更为强大，支持连接池管理等高级特性：

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 {
        try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
            HttpGet request = new HttpGet("https://api.example.com/data");
            
            try (CloseableHttpResponse response = httpClient.execute(request)) {
                System.out.println("状态码: " + response.getStatusLine().getStatusCode());
                String result = EntityUtils.toString(response.getEntity());
                System.out.println("响应体: " + result);
            }
        }
    }
}

此方案适合需要频繁发起HTTP请求的场景，通过连接池可以显著提升性能。4.5+版本开始支持HTTP/2协议，需要添加Maven依赖：

xml <dependency> <groupId>org.apache.httpcomponents</groupId> <artifactId>httpclient</artifactId> <version>4.5.13</version> </dependency>

三、OkHttp高效方案

Square公司开源的OkHttp是目前最流行的HTTP客户端之一，具有简洁的API和优异的性能：

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://api.example.com/data")
                .get()
                .build();
        
        try (Response response = client.newCall(request).execute()) {
            System.out.println("响应码: " + response.code());
            System.out.println("响应体: " + response.body().string());
        }
    }
}

OkHttp默认支持HTTP/2和连接复用，自动处理GZIP压缩，特别适合移动端应用开发。添加依赖：

xml <dependency> <groupId>com.squareup.okhttp3</groupId> <artifactId>okhttp</artifactId> <version>4.10.0</version> </dependency>

最佳实践建议

1. 超时设置：所有方案都必须配置连接超时和读取超时
2. 异常处理：需要捕获IOException等网络异常
3. 资源释放：确保关闭所有IO资源
4. 性能考量：高频请求场景优先使用OkHttp或HttpClient
5. HTTPS支持：新版本库默认支持TLSv1.2+

根据项目实际情况选择方案：轻量级需求可用HttpURLConnection，传统Java项目适合HttpClient，而追求性能和现代特性的项目推荐OkHttp。