Apache HttpClient 5 用法-Java调用http服务_org.apache.hc.client5

Apache HttpClient 5 核心用法详解

Apache HttpClient 5 是 Apache 基金会推出的新一代 HTTP 客户端库，相比 4.x 版本在性能、模块化和易用性上有显著提升。以下是其核心用法及最佳实践：

一、添加依赖

Maven 项目：

 org.apache.httpcomponents.client5 httpclient5 5.4-alpha1 

Gradle 项目：

implementation \'org.apache.httpcomponents.client5:httpclient5:5.4-alpha1\'

二、基础用法

1. 创建 HttpClient 实例

import org.apache.hc.client5.http.classic.methods.HttpGet;import org.apache.hc.client5.http.classic.methods.HttpPost;import org.apache.hc.client5.http.impl.classic.CloseableHttpClient;import org.apache.hc.client5.http.impl.classic.HttpClients;import org.apache.hc.core5.http.ClassicHttpResponse;import org.apache.hc.core5.http.HttpEntity;import org.apache.hc.core5.http.io.entity.EntityUtils;import org.apache.hc.core5.http.io.entity.StringEntity;// 创建带连接池的客户端（默认连接池大小：2*CPU核心数）CloseableHttpClient httpClient = HttpClients.custom() .setConnectionManagerShared(true) // 共享连接池（推荐） .setDefaultRequestConfig(RequestConfig.custom() .setConnectTimeout(5000) // 连接超时（毫秒） .setResponseTimeout(10000) // 响应超时 .build()) .build();

2. 发送 GET 请求

HttpGet httpGet = new HttpGet(\"https://api.example.com/data\");try (CloseableHttpClient client = HttpClients.createDefault()) { try (CloseableHttpResponse response = client.execute(httpGet)) { HttpEntity entity = response.getEntity(); String result = EntityUtils.toString(entity); System.out.println(\"Status: \" + response.getCode() + \", Body: \" + result); }}

3. 发送 POST 请求（提交 JSON）

HttpPost httpPost = new HttpPost(\"https://api.example.com/post\");String jsonBody = \"{\\\"key\\\":\\\"value\\\"}\";httpPost.setEntity(new StringEntity(jsonBody, ContentType.APPLICATION_JSON));try (CloseableHttpClient client = HttpClients.createDefault()) { try (CloseableHttpResponse response = client.execute(httpPost)) { HttpEntity entity = response.getEntity(); String result = EntityUtils.toString(entity); System.out.println(\"Status: \" + response.getCode() + \", Body: \" + result); }}

三、高级功能

1. 连接池配置（优化性能）

PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();cm.setMaxTotal(100); // 最大连接数cm.setDefaultMaxPerRoute(20); // 每个路由默认最大连接数CloseableHttpClient client = HttpClients.custom() .setConnectionManager(cm) .build();

2. 自定义 Header 和 Cookie

HttpGet httpGet = new HttpGet(\"https://api.example.com/data\");httpGet.setHeader(\"User-Agent\", \"Apache HttpClient 5\");httpGet.setHeader(\"Authorization\", \"Bearer token123\");// 添加 CookieBasicCookieStore cookieStore = new BasicCookieStore();BasicClientCookie cookie = new BasicClientCookie(\"session_id\", \"abc123\");cookie.setDomain(\"api.example.com\");cookieStore.addCookie(cookie);CloseableHttpClient client = HttpClients.custom() .setDefaultCookieStore(cookieStore) .build();

3. 文件上传（Multipart）

HttpPost httpPost = new HttpPost(\"https://api.example.com/upload\");MultipartEntityBuilder builder = MultipartEntityBuilder.create();builder.addBinaryBody(\"file\", new File(\"path/to/file.jpg\"), ContentType.MULTIPART_FORM_DATA, \"file.jpg\");builder.addTextBody(\"description\", \"Test upload\", ContentType.TEXT_PLAIN);httpPost.setEntity(builder.build());try (CloseableHttpClient client = HttpClients.createDefault()) { try (CloseableHttpResponse response = client.execute(httpPost)) { // 处理响应 }}

4. 异步请求（非阻塞）

HttpClientAsyncClient asyncClient = HttpClients.createAsyncDefault();HttpGet httpGet = new HttpGet(\"https://api.example.com/data\");asyncClient.execute(httpGet, new FutureCallback() { @Override public void completed(ClassicHttpResponse response) { HttpEntity entity = response.getEntity(); String result = EntityUtils.toString(entity); System.out.println(\"Async Response: \" + result); } @Override public void failed(Exception ex) { ex.printStackTrace(); } @Override public void cancelled() { System.out.println(\"Request cancelled\"); }});// 主线程继续执行其他任务Thread.sleep(5000); // 等待异步结果（实际需用 CountDownLatch 等机制）

四、迁移指南（从 HttpClient 4.x）

1. 包名变化：

   • org.apache.http.client.HttpClient → org.apache.hc.client5.http.classic.HttpClient
   • HttpGet/HttpPost 等类路径调整。

2. API 调整：

   • 响应处理：CloseableHttpResponse 替代 CloseableHttpResponse（方法名类似）。
   • 连接池管理：使用 PoolingHttpClientConnectionManager 替代 PoolingHttpClientConnectionManager。

3. 移除废弃方法：

   • 如 HttpClientBuilder.setMaxConnPerRoute() 改为 setMaxConnPerRoute(Route, int)。

五、最佳实践

1. 复用 HttpClient 实例：避免频繁创建/销毁，推荐使用 HttpClients.custom().build() 创建单例。
2. 资源释放：使用 try-with-resources 确保 CloseableHttpClient 和 CloseableHttpResponse 正确关闭。
3. 异常处理：捕获 IOException 和 HttpRequestException，处理网络错误和 HTTP 状态码。
4. 性能监控：通过 ConnectionStats 监控连接池使用情况。

通过以上内容，您已掌握 Apache HttpClient 5 的核心用法，可根据项目需求实现高效、稳定的 HTTP 通信。如需处理复杂场景（如 OAuth2 认证、WebSocket），可进一步探索其扩展模块。