HttpClient修仙大典：从HTTP小厮到请求天尊的终极飞升指南

一、筑基篇：初识HttpClient

1.1 选择你的本命法宝

<dependency>
    <groupId>org.apache.httpcomponentsgroupId>
    <artifactId>httpclientartifactId>
    <version>4.5.13version>
dependency>


// 直接调用 java.net.http.HttpClient

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二、金丹篇：基础HTTP请求

2.1 GET请求（灵气采集）

// Java 11+ 标准库版
HttpClient client = HttpClient.newHttpClient();
HttpRequest request = HttpRequest.newBuilder()
        .uri(URI.create("https://api.example.com/data"))
        .GET()
        .build();

HttpResponse<String> response = client.send(request, HttpResponse.BodyHandlers.ofString());
System.out.println("状态码：" + response.statusCode());
System.out.println("响应体：" + response.body());

2.2 POST请求（灵力输送）

// 发送JSON数据（附赠护体结界）
String jsonBody = "{\"name\":\"张三\",\"age\":25}";

HttpRequest request = HttpRequest.newBuilder()
        .uri(URI.create("https://api.example.com/users"))
        .header("Content-Type", "application/json")
        .POST(HttpRequest.BodyPublishers.ofString(jsonBody))
        .build();

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

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三、元婴篇：高级配置秘籍

3.1 超时设置（防渡劫超时）

HttpClient client = HttpClient.newBuilder()
        .connectTimeout(Duration.ofSeconds(5)) // 连接超时
        .followRedirects(HttpClient.Redirect.NORMAL) // 自动重定向
        .version(HttpClient.Version.HTTP_2) // 启用HTTP/2
        .build();

3.2 伪装大法（User-Agent伪装）

HttpRequest request = HttpRequest.newBuilder()
        .header("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_7)")
        .header("Accept-Language", "zh-CN,zh;q=0.9")
        .build();

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四、化神篇：处理复杂场景

4.1 异步请求（分身渡劫术）

client.sendAsync(request, HttpResponse.BodyHandlers.ofString())
        .thenApply(HttpResponse::body)
        .thenAccept(System.out::println)
        .exceptionally(e -> {
            System.err.println("渡劫失败：" + e.getMessage());
            return null;
        });
// 主线程可继续执行其他任务

4.2 文件上传（乾坤大挪移）

// 构建multipart/form-data
String boundary = "----WebKitFormBoundary" + System.currentTimeMillis();
HttpRequest request = HttpRequest.newBuilder()
        .header("Content-Type", "multipart/form-data; boundary=" + boundary)
        .POST(ofMimeMultipartData(
            Map.of("name", "张三", "file", Path.of("report.pdf")), 
            boundary))
        .build();

// 需要自定义BodyPublisher（代码略长，建议封装工具类）

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五、大乘篇：安全与异常处理

5.1 SSL证书信任（慎用！）

HttpClient client = HttpClient.newBuilder()
        .sslContext(insecureSSLContext()) // 自定义信任所有证书
        .build();

// 信任所有证书方法（测试环境专用！）
private static SSLContext insecureSSLContext() throws Exception {
    TrustManager[] trustAll = new TrustManager[]{new X509TrustManager() {
        public void checkClientTrusted(X509Certificate[] chain, String authType) {}
        public void checkServerTrusted(X509Certificate[] chain, String authType) {}
        public X509Certificate[] getAcceptedIssuers() { return new X509Certificate[0]; }
    }};
    SSLContext sc = SSLContext.getInstance("SSL");
    sc.init(null, trustAll, new SecureRandom());
    return sc;
}

5.2 异常处理（渡劫护体诀）

try {
    HttpResponse<String> response = client.send(request, BodyHandlers.ofString());
    if (response.statusCode() >= 400) {
        System.err.println("请求异常：" + response.body());
    }
} catch (IOException e) {
    System.err.println("IO异常：" + e.getMessage());
} catch (InterruptedException e) {
    System.err.println("请求中断：" + e.getMessage());
    Thread.currentThread().interrupt();
}

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六、飞升篇：性能优化

6.1 连接池管理（节省灵力）

// Apache HttpClient配置
PoolingHttpClientConnectionManager cm = new PoolingHttpClientConnectionManager();
cm.setMaxTotal(200); // 最大连接数
cm.setDefaultMaxPerRoute(20); // 单路由最大连接

CloseableHttpClient client = HttpClients.custom()
        .setConnectionManager(cm)
        .build();

6.2 请求压缩（缩地成寸）

HttpRequest request = HttpRequest.newBuilder()
        .header("Accept-Encoding", "gzip, deflate") // 启用压缩
        .build();

// 自动解压响应（Java HttpClient默认支持）

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渡劫成功总结

1. 版本选择：旧项目用Apache版，Java 11+用标准库版
2. 最佳实践：重用HttpClient实例、合理设置超时
3. 安全守则：生产环境严格校验SSL证书
4. 性能心法：连接池+异步请求+压缩传输

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飞升后选择：

• 深度修炼：研究WebSocket/RESTful高级集成
• 法宝升级：尝试OkHttp或Retrofit等现代库
• 跨界融合：整合到Spring生态的RestTemplate