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Apache HttpClient使用实例详解

作者:kmt-码上解决

ApacheHttpClient是一个强大的Java HTTP客户端库,用于发送HTTP请求并处理响应,HttpClients提供了多种方法来创建和配置HTTP客户端实例,本文给大家介绍Apache HttpClient使用示例详解,感兴趣的朋友一起看看吧

一、Apache HttpClient 基础版

HttpClients 是 Apache HttpClient 库中的一个工具类,用于创建和管理 HTTP 客户端实例。Apache HttpClient 是一个强大的 Java HTTP 客户端库,用于发送 HTTP 请求并处理 HTTP 响应。HttpClients 提供了多种方法来创建和配置 HTTP 客户端实例。

以下是关于 HttpClients 的详细讲解:

1. Apache HttpClient 简介

Apache HttpClient 是一个开源的 Java HTTP 客户端库,支持 HTTP/1.1 和 HTTP/2 协议。它提供了丰富的功能,例如:

2. HttpClients 类的作用

HttpClients 是一个工厂类,用于创建 CloseableHttpClient 实例。CloseableHttpClient 是 HTTP 客户端的主要接口,用于执行 HTTP 请求。

HttpClients 提供了多种静态方法来创建和配置 HTTP 客户端实例,例如:

3. HttpClients 的常用方法

(1) HttpClients.createDefault()

CloseableHttpClient httpClient = HttpClients.createDefault();

(2) HttpClients.createSystem()

CloseableHttpClient httpClient = HttpClients.createSystem();

(3) HttpClients.custom()

 CloseableHttpClient httpClient = HttpClients.custom()
     .setMaxConnTotal(100) // 最大连接数
     .setMaxConnPerRoute(10) // 每个路由的最大连接数
     .build();

4. HttpClients 的使用示例

以下是一个完整的示例,展示如何使用 HttpClients 发送 HTTP GET 请求并处理响应:

 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) {
         // 1. 创建 HTTP 客户端
         try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
             // 2. 创建 HTTP GET 请求
             HttpGet request = new HttpGet("https://jsonplaceholder.typicode.com/posts/1");
 ​
             // 3. 发送请求并获取响应
             try (CloseableHttpResponse response = httpClient.execute(request)) {
                 // 4. 检查响应状态码
                 int statusCode = response.getStatusLine().getStatusCode();
                 System.out.println("Status Code: " + statusCode);
 ​
                 // 5. 获取响应内容
                 String responseBody = EntityUtils.toString(response.getEntity());
                 System.out.println("Response Body: " + responseBody);
             }
         } catch (Exception e) {
             e.printStackTrace();
         }
     }
 }

5. HttpClients 的高级配置

通过 HttpClients.custom() 方法,可以自定义 HTTP 客户端的配置。以下是一些常见的配置选项:

(1) 连接池配置

 CloseableHttpClient httpClient = HttpClients.custom()
     .setMaxConnTotal(100) // 最大连接数
     .setMaxConnPerRoute(10) // 每个路由的最大连接数
     .build();

(2) 超时配置

 RequestConfig requestConfig = RequestConfig.custom()
     .setConnectTimeout(5000) // 连接超时时间
     .setSocketTimeout(5000) // 读取超时时间
     .build();
 ​
 CloseableHttpClient httpClient = HttpClients.custom()
     .setDefaultRequestConfig(requestConfig)
     .build();

(3) 代理配置

 HttpHost proxy = new HttpHost("proxy.example.com", 8080);
 ​
 CloseableHttpClient httpClient = HttpClients.custom()
     .setProxy(proxy)
     .build();

(4) SSL/TLS 配置

 SSLContext sslContext = SSLContexts.custom()
     .loadTrustMaterial((chain, authType) -> true) // 信任所有证书
     .build();
 ​
 CloseableHttpClient httpClient = HttpClients.custom()
     .setSSLContext(sslContext)
     .build();

6. 注意事项

资源释放CloseableHttpClientCloseableHttpResponse 都实现了 Closeable 接口,使用后需要关闭以释放资源。

线程安全CloseableHttpClient 是线程安全的,可以在多线程环境中共享。

性能优化: 使用连接池和合理的超时配置可以显著提升性能。

7. 总结

二、Apache HttpClient 高级版

1. HttpClients 类概述

HttpClients 是 Apache HttpClient 库中的一个工厂类,用于创建和配置 CloseableHttpClient 实例。它是构建 HTTP 客户端的入口点,支持高度自定义的 HTTP 请求处理,包括连接池管理、SSL/TLS 配置、重试机制等。

2. 核心方法与配置

2.1 创建默认客户端

CloseableHttpClient httpClient = HttpClients.createDefault();

特点

2.2 自定义配置客户端

通过 HttpClients.custom() 返回 HttpClientBuilder,允许精细化配置:

 CloseableHttpClient httpClient = HttpClients.custom()
     .setConnectionManager(connectionManager)  // 连接池管理
     .setDefaultRequestConfig(requestConfig)   // 请求超时配置
     .setRetryHandler(retryHandler)            // 请求重试策略
     .setProxy(proxy)                          // 代理设置
     .setSSLContext(sslContext)                // SSL/TLS 配置
     .build();

3. 高级配置详解

3.1 连接池管理

连接池是提升性能的关键组件,避免频繁创建和销毁连接。

 PoolingHttpClientConnectionManager connectionManager = 
     new PoolingHttpClientConnectionManager();
 connectionManager.setMaxTotal(200);          // 最大总连接数
 connectionManager.setDefaultMaxPerRoute(20); // 每个路由(目标主机)的最大连接数
 ​
 CloseableHttpClient httpClient = HttpClients.custom()
     .setConnectionManager(connectionManager)
     .build();

3.2 超时配置

 RequestConfig requestConfig = RequestConfig.custom()
     .setConnectTimeout(5000)    // 连接建立超时时间(毫秒)
     .setSocketTimeout(10000)     // 数据传输超时时间(毫秒)
     .setConnectionRequestTimeout(2000) // 从连接池获取连接的超时时间
     .build();
 ​
 CloseableHttpClient httpClient = HttpClients.custom()
     .setDefaultRequestConfig(requestConfig)
     .build();

3.3 重试机制

自动重试失败的请求(例如网络波动导致失败):

 HttpRequestRetryHandler retryHandler = (exception, executionCount, context) -> {
     if (executionCount >= 3) return false; // 最大重试次数
     if (exception instanceof NoHttpResponseException) return true; // 无响应时重试
     return false;
 };
 ​
 CloseableHttpClient httpClient = HttpClients.custom()
     .setRetryHandler(retryHandler)
     .build();

3.4 代理配置

 HttpHost proxy = new HttpHost("proxy.example.com", 8080);
 CloseableHttpClient httpClient = HttpClients.custom()
     .setProxy(proxy)
     .build();

3.5 SSL/TLS 配置

信任所有证书(仅限测试环境):

 SSLContext sslContext = SSLContexts.custom()
     .loadTrustMaterial((chain, authType) -> true) // 信任所有证书
     .build();
 ​
 CloseableHttpClient httpClient = HttpClients.custom()
     .setSSLContext(sslContext)
     .setSSLHostnameVerifier(NoopHostnameVerifier.INSTANCE) // 跳过主机名验证
     .build();

3.6 认证机制

使用 Basic 认证:

 CredentialsProvider credentialsProvider = new BasicCredentialsProvider();
 credentialsProvider.setCredentials(
     new AuthScope("host.example.com", 80),
     new UsernamePasswordCredentials("user", "pass")
 );
 ​
 CloseableHttpClient httpClient = HttpClients.custom()
     .setDefaultCredentialsProvider(credentialsProvider)
     .build();

4. 请求与响应处理

4.1 发送 GET 请求

 HttpGet httpGet = new HttpGet("https://api.example.com/data");
 try (CloseableHttpResponse response = httpClient.execute(httpGet)) {
     int statusCode = response.getStatusLine().getStatusCode();
     HttpEntity entity = response.getEntity();
     String content = EntityUtils.toString(entity);
     EntityUtils.consume(entity); // 确保资源释放
 }

4.2 发送 POST 请求(JSON 数据)

 HttpPost httpPost = new HttpPost("https://api.example.com/create");
 StringEntity jsonEntity = new StringEntity("{\"key\":\"value\"}", ContentType.APPLICATION_JSON);
 httpPost.setEntity(jsonEntity);
 ​
 try (CloseableHttpResponse response = httpClient.execute(httpPost)) {
     // 处理响应...
 }

4.3 文件上传(Multipart)

 HttpPost httpPost = new HttpPost("https://api.example.com/upload");
 FileBody fileBody = new FileBody(new File("path/to/file"));
 MultipartEntityBuilder builder = MultipartEntityBuilder.create()
     .addPart("file", fileBody)
     .addTextBody("comment", "File upload");
 httpPost.setEntity(builder.build());

5. 高级功能

5.1 异步请求

使用 HttpAsyncClients 实现异步非阻塞请求:

 CloseableHttpAsyncClient asyncClient = HttpAsyncClients.custom().build();
 asyncClient.start();
 ​
 SimpleHttpRequest request = SimpleHttpRequest.get("https://api.example.com/data");
 Future<SimpleHttpResponse> future = asyncClient.execute(request, new FutureCallback<>() {
     @Override
     public void completed(SimpleHttpResponse response) {
         System.out.println("Response: " + response.getBodyText());
     }
 ​
     @Override
     public void failed(Exception ex) {
         ex.printStackTrace();
     }
 ​
     @Override
     public void cancelled() {
         System.out.println("Request cancelled");
     }
 });

5.2 请求拦截器

添加自定义逻辑(如日志记录、修改请求头):

 CloseableHttpClient httpClient = HttpClients.custom()
     .addInterceptorFirst((HttpRequestInterceptor) (request, context) -> {
         request.addHeader("X-Custom-Header", "value");
         System.out.println("Request URI: " + request.getRequestLine().getUri());
     })
     .build();

5.3 Cookie 管理

自动管理 Cookie:

 CookieStore cookieStore = new BasicCookieStore();
 CloseableHttpClient httpClient = HttpClients.custom()
     .setDefaultCookieStore(cookieStore)
     .build();

6. 最佳实践与常见问题

6.1 资源释放

确保关闭 CloseableHttpClientCloseableHttpResponse

 try (CloseableHttpClient httpClient = HttpClients.createDefault()) {
     try (CloseableHttpResponse response = httpClient.execute(request)) {
         // 处理响应...
     }
 }

6.2 性能调优

6.3 错误处理

6.4 安全性

7. 典型应用场景

8. 官方文档与资源

Apache HttpClient 官方文档Apache HttpComponents – HttpClient Overview

GitHub 仓库https://github.com/apache/httpcomponents-client

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