从Python Requests到libcpr/cpr：C++开发者的无缝过渡-优快云博客

从Python Requests到libcpr/cpr：C++开发者的无缝过渡

【免费下载链接】cpr 项目地址: https://gitcode.com/gh_mirrors/cpr/cpr

你是否在C++项目中苦于处理复杂的网络请求？是否怀念Python Requests库简洁直观的API？本文将带你实现从Python Requests到C++网络库libcpr/cpr的平滑过渡，用熟悉的编程模式解决C++网络编程难题。读完本文，你将能够：掌握libcpr的核心API，实现常见HTTP请求，处理认证、超时等高级功能，以及编写异步网络代码。

为什么选择libcpr/cpr？

libcpr/cpr（C++ Requests）是一个基于libcurl的C++网络库，灵感来源于Python Requests项目。它解决了原生libcurl接口复杂、容易出错的问题，利用C++17的语言特性，将网络请求封装为简洁易懂的API。

主要优势：

与Python Requests相似的直观API设计
完整支持HTTP/HTTPS协议
线程安全的libcurl访问
支持异步请求和连接池
简洁的错误处理机制

项目核心文件结构：

主头文件：include/cpr/cpr.h
请求实现：cpr/session.cpp、cpr/response.cpp
测试示例：test/get_tests.cpp、test/post_tests.cpp

环境准备与安装

系统要求

C++17兼容编译器（GCC、Clang等）
CMake 3.14+
OpenSSL开发库（用于HTTPS支持）

安装方式

CMake FetchContent（推荐）

在你的CMakeLists.txt中添加：

include(FetchContent)
FetchContent_Declare(cpr GIT_REPOSITORY https://gitcode.com/gh_mirrors/cpr/cpr
                         GIT_TAG 3b15fa82ea74739b574d705fea44959b58142eb8)
FetchContent_MakeAvailable(cpr)

target_link_libraries(your_target_name PRIVATE cpr::cpr)

手动编译安装

git clone https://gitcode.com/gh_mirrors/cpr/cpr
cd cpr && mkdir build && cd build
cmake .. -DCPR_USE_SYSTEM_CURL=ON
cmake --build . --parallel
sudo cmake --install .

在项目中使用：

find_package(cpr REQUIRED)
target_link_libraries(your_target_name PRIVATE cpr::cpr)

核心API对比：Python Requests vs libcpr

基本GET请求

Python Requests:

import requests

response = requests.get('https://api.example.com/data', 
                        params={'key': 'value'},
                        timeout=5)
print(response.status_code)
print(response.json())

libcpr/cpr:

#include <cpr/cpr.h>
#include <iostream>

int main() {
    cpr::Response r = cpr::Get(cpr::Url{"https://api.example.com/data"},
                      cpr::Parameters{{"key", "value"}},
                      cpr::Timeout{5000}); // 超时时间，单位毫秒
    std::cout << r.status_code << std::endl;
    std::cout << r.text << std::endl;
    return 0;
}

请求参数与响应处理

Python Requests:

response = requests.get('https://api.example.com/data',
                        params={'page': 1, 'limit': 10})
print(f"状态码: {response.status_code}")
print(f"响应头: {response.headers['Content-Type']}")
print(f"响应内容: {response.text}")

libcpr/cpr:

cpr::Response r = cpr::Get(cpr::Url{"https://api.example.com/data"},
                  cpr::Parameters{{"page", "1"}, {"limit", "10"}});
std::cout << "状态码: " << r.status_code << std::endl;
std::cout << "响应头: " << r.header["content-type"] << std::endl;
std::cout << "响应内容: " << r.text << std::endl;

高级功能实现

认证处理

基本认证 (Basic Authentication)

Python Requests:

response = requests.get('https://api.example.com/secret',
                        auth=('user', 'pass'))

libcpr/cpr:

cpr::Response r = cpr::Get(cpr::Url{"https://api.example.com/secret"},
                  cpr::Authentication{"user", "pass", cpr::AuthMode::BASIC});

Bearer Token认证

Python Requests:

headers = {'Authorization': 'Bearer YOUR_TOKEN'}
response = requests.get('https://api.example.com/data', headers=headers)

libcpr/cpr:

cpr::Response r = cpr::Get(cpr::Url{"https://api.example.com/data"},
                  cpr::Bearer{"YOUR_TOKEN"});

POST请求与数据提交

表单数据提交

Python Requests:

data = {'name': 'John', 'age': '30'}
response = requests.post('https://api.example.com/users', data=data)

libcpr/cpr:

cpr::Response r = cpr::Post(cpr::Url{"https://api.example.com/users"},
                   cpr::Payload{{"name", "John"}, {"age", "30"}});

JSON数据提交

Python Requests:

import json
data = {'name': 'John', 'age': 30}
response = requests.post('https://api.example.com/users', 
                         json=data)

libcpr/cpr:

cpr::Response r = cpr::Post(cpr::Url{"https://api.example.com/users"},
                   cpr::Header{{"Content-Type", "application/json"}},
                   cpr::Body{R"({"name":"John","age":30})"});

文件上传

Python Requests:

files = {'file': open('document.pdf', 'rb')}
response = requests.post('https://api.example.com/upload', files=files)

libcpr/cpr:

cpr::Response r = cpr::Post(cpr::Url{"https://api.example.com/upload"},
                   cpr::Multipart{{"file", cpr::File{"document.pdf"}}});

异步请求处理

异步GET请求

Python Requests (使用requests-futures):

from requests_futures.sessions import FuturesSession

session = FuturesSession()
future = session.get('https://api.example.com/data')
# 执行其他任务
response = future.result()
print(response.text)

libcpr/cpr:

cpr::AsyncResponse future = cpr::GetAsync(cpr::Url{"https://api.example.com/data"});
// 执行其他任务
cpr::Response r = future.get();
std::cout << r.text << std::endl;

多异步请求

libcpr/cpr:

std::vector<cpr::AsyncResponse> futures;
futures.emplace_back(cpr::GetAsync(cpr::Url{"https://api.example.com/data1"}));
futures.emplace_back(cpr::GetAsync(cpr::Url{"https://api.example.com/data2"}));

for (auto& future : futures) {
    cpr::Response r = future.get();
    std::cout << "状态码: " << r.status_code << ", 内容: " << r.text << std::endl;
}

超时与错误处理

设置超时

Python Requests:

try:
    response = requests.get('https://api.example.com/data', 
                            timeout=5)  # 5秒超时
except requests.exceptions.Timeout:
    print("请求超时")

libcpr/cpr:

cpr::Response r = cpr::Get(cpr::Url{"https://api.example.com/data"},
                  cpr::Timeout{5000},  // 5000毫秒超时
                  cpr::ConnectTimeout{2000});  // 连接超时2秒
if (r.status_code == 0) {
    std::cerr << "请求超时或失败: " << r.error.message << std::endl;
}

错误处理

Python Requests:

try:
    response = requests.get('https://api.example.com/data')
    response.raise_for_status()
except requests.exceptions.HTTPError as e:
    print(f"HTTP错误: {e}")
except requests.exceptions.RequestException as e:
    print(f"请求异常: {e}")

libcpr/cpr:

cpr::Response r = cpr::Get(cpr::Url{"https://api.example.com/data"});
if (!r.error) {
    if (r.status_code >= 200 && r.status_code < 300) {
        // 请求成功
        std::cout << r.text << std::endl;
    } else {
        std::cerr << "HTTP错误: " << r.status_code << std::endl;
    }
} else {
    std::cerr << "请求错误: " << r.error.message << std::endl;
}

会话管理与高级配置

会话复用

Python Requests:

with requests.Session() as session:
    session.headers.update({'User-Agent': 'My App'})
    session.get('https://api.example.com/login', params={'token': 'abc'})
    response = session.get('https://api.example.com/data')

libcpr/cpr:

cpr::Session session;
session.SetUrl(cpr::Url{"https://api.example.com"});
session.SetHeader(cpr::Header{{"User-Agent", "My App"}});

// 登录
session.SetParameters(cpr::Parameters{{"token", "abc"}});
session.Get();

// 复用会话获取数据
session.SetUrl(cpr::Url{"https://api.example.com/data"});
cpr::Response response = session.Get();

实战示例：REST API客户端

下面是一个完整的libcpr/cpr使用示例，实现一个简单的REST API客户端：

#include <cpr/cpr.h>
#include <iostream>
#include <nlohmann/json.hpp>  // 需要安装nlohmann/json库

using json = nlohmann::json;

class ApiClient {
private:
    std::string base_url;
    cpr::Session session;

public:
    ApiClient(std::string url) : base_url(std::move(url)) {
        // 设置通用头部
        session.SetHeader(cpr::Header{
            {"Content-Type", "application/json"},
            {"User-Agent", "libcpr Client"}
        });
        // 设置超时
        session.SetTimeout(cpr::Timeout{10000});
    }

    void set_auth_token(const std::string& token) {
        session.SetHeader(cpr::Header{{"Authorization", "Bearer " + token}});
    }

    json get(const std::string& endpoint) {
        session.SetUrl(cpr::Url{base_url + endpoint});
        auto response = session.Get();
        
        if (response.status_code != 200) {
            throw std::runtime_error("GET请求失败: " + std::to_string(response.status_code));
        }
        
        return json::parse(response.text);
    }

    json post(const std::string& endpoint, const json& data) {
        session.SetUrl(cpr::Url{base_url + endpoint});
        session.SetBody(cpr::Body{data.dump()});
        auto response = session.Post();
        
        if (response.status_code < 200 || response.status_code >= 300) {
            throw std::runtime_error("POST请求失败: " + std::to_string(response.status_code));
        }
        
        return json::parse(response.text);
    }
};

int main() {
    try {
        ApiClient client("https://api.example.com/v1/");
        client.set_auth_token("YOUR_AUTH_TOKEN");
        
        // 获取数据
        auto users = client.get("users");
        std::cout << "用户列表: " << users.dump(4) << std::endl;
        
        // 创建新用户
        json new_user = {{"name", "New User"}, {"email", "user@example.com"}};
        auto created_user = client.post("users", new_user);
        std::cout << "创建用户: " << created_user.dump(4) << std::endl;
        
    } catch (const std::exception& e) {
        std::cerr << "发生错误: " << e.what() << std::endl;
        return 1;
    }
    return 0;
}

总结与进阶

通过本文的介绍，你已经掌握了libcpr/cpr的核心用法，能够实现从Python Requests到C++的平滑过渡。libcpr/cpr提供了与Python Requests相似的API设计，同时保持了C++的性能优势。

进阶学习资源：

官方测试用例：test/目录包含各种功能的示例代码
异步编程：探索cpr/async.cpp和cpr/threadpool.cpp了解异步实现原理
拦截器功能：通过test/interceptor_tests.cpp学习请求/响应拦截

libcpr/cpr是一个活跃发展的项目，定期更新新功能和改进。建议关注项目的README.md获取最新信息和版本更新。

希望本文能帮助你在C++项目中更高效地处理网络请求。如果你有任何问题或使用心得，欢迎在评论区分享交流！

【免费下载链接】cpr 项目地址: https://gitcode.com/gh_mirrors/cpr/cpr

创作声明：本文部分内容由AI辅助生成（AIGC），仅供参考