#头条创作挑战赛#

前言

一般的用客户端实现Webservice有两种方式，一种是基于SOAP协议，另外一种是基于REST，并且REST协议目前是越来越流行。使用C#或者java来开发REST客户端目前是比较快捷方便的，毕竟可用的库或资源很多，但使用C++开发REST client的话就不容易了，毕竟标准C++在网络库这一块是没有标注库的，以前开发时候使用过libcurl库（C语言编写）和VC++ 的http client，或者使用Qt的QNetworkAccessManager库来进行后台api的调用，实现post、get请求进行数据处理，但或多或少都遇到过一些问题，再到后来别人推荐了微软开源的casablanca，或者叫cppRestSdk库。下面整理一下cppRestSdk库的使用及一些入门示例代码。

1、cpprestsdk介绍及编译

c++REST SDK，又叫卡萨布兰卡，是一个微软发布的C++基于云的客户机-服务器通信库。该库基于现代化的C++异步API，即Promise模型或叫链式异步模型设计，c++开发人员可以方便地连接并与服务交互。

SDK内容

特性——HTTP客户机/服务器，JSON，URI，异步流，WebSockets客户机,oAuthPPL任务[2] ——一个强大的基于c++11特性编写的异步操作模型支持平台——Windows桌面，Windows Store，Windows Phone，Ubuntu，OS X，iOS和AndroidWindows平台编译支持——VS 2012、2013年、2015、2017、2019非Windows平台编译支持——cmake包管理器支持——NuGet，仅在VS编译器支持Windows和Android平台

cpprestsdk编译

cpprestsdk的源代码可以在github下载：，但编译的过程比较复杂，因为依赖了boost、openssl等库，需要先编译这些库。常用方法有下面三种：

github下载

（1）使用vcpkg安装，但vcpkg这个工具本身需要先下载依赖库的各种源码，此外下载过程中很容易出现资源下载不下来的问题，相对较为麻烦，优点是自动化，只要解决vcpkg下载中的各种问题，编译什么的都是自动的。

（2）使用Visual studio自带的NuGet package包管理器。在visual studio 新建一个c++工程，点击 “工具——NuGet 程序包管理器——管理解决方案的NuGet 程序包”，打开NuGet包管理器。然后搜索cpprestsdk即可找到，本人用的VS2017IDE，效果如下：

点击“安装”按钮进行安装，安装完成后，visual studio自动将cpprestsdk （编译后的lib、include头文件、dll文件）下载到当前项目工程文件所在的路径中。

当然为了方便实用，也可以将编译后的lib、include头文件、dll文件拷贝到自己指定的文件夹下，作为普通的第三方库进行使用。

2、cpprestsdk官方示例

官方示例提供的是一个Get请求，获取url = " github"返回的html文件，运行结果是将请求到的html网页数据流保存生成results.html文件。

运行结果

示例代码如下：

#include "stdafx.h"#include <cpprest/http_client.h>#include <cpprest/filestream.h>using namespace utility; // Common utilities like string conversionsusing namespace web; // Common features like URIs.using namespace web::http; // Common HTTP functionalityusing namespace web::http::client; // HTTP client featuresusing namespace concurrency::streams; // Asynchronous streams// 官方示例//Get请求：获取url = " github"返回的html文件；//运行结果：将请求到的html网页数据流保存生成results.html文件/* std::wstring wsServersite = L";;std::wstring wsURI = L"/search";std::wstring wsName = L"q";std::wstring wsValue = L"cpprestsdk github";*/void OfficialExample(const std::wstring& wsServersite, const std::wstring& wsURI, const std::wstring& wsURIName, const std::wstring& wsURIValue){auto fileStream = std::make_shared<ostream>();// Open stream to output file.pplx::task<void> requestTask = fstream::open_ostream(U("../x64/results.html")).then([=](ostream outFile){*fileStream = outFile;// Create http_client to send the request.http_client client(wsServersite); //wsServersite =  Build request URI and start the request.uri_builder builder(wsURI);builder.append_query(wsURIName, wsURIValue);//std::wstring s1 = builder.to_string().c_str();//std::wcout << s1 << std::endl;return client.request(methods::GET, builder.to_string());})// Handle response headers arriving..then([=](http_response response){printf("Received response status code:%u\n", response.status_code());// Write response body into the file.return response.body().read_to_end(fileStream->streambuf());})// Close the file stream..then([=](size_t){return fileStream->close();});// Wait for all the outstanding I/O to complete and handle any exceptionstry{requestTask.wait();}catch (const std::exception &e){printf("Error exception:%s\n", e.what());}}int main(int argc, char* argv[]){// 官方示例测试std::wstring wsServersite = L";;std::wstring wsURI = L"/search";std::wstring wsName = L"q";std::wstring wsValue = L"cpprestsdk github";OfficialExample(wsServersite, wsURI, wsName, wsValue);}

官方代码用的C++11新特性.then实现的异步请求，如果不适应的话可以改为同步请求数据：

void OfficialExample(){auto fileStream = std::make_shared<ostream>();ostream outFile = fstream::open_ostream(U("results.html")).get();*fileStream = outFile;// Create http_client to send the request.http_client client(U(";));// Build request URI and start the request.uri_builder builder(U("/search"));builder.append_query(U("q"), U("cpprestsdk github"));http_response response = client.request(methods::GET, builder.to_string()).get();// Write response body into the file.response.body().read_to_end(fileStream->streambuf()).get();fileStream->close().get();}

1）POST接口使用：

#include "stdafx.h"#include <cpprest/http_client.h>#include <cpprest/filestream.h>using namespace utility; // Common utilities like string conversionsusing namespace web; // Common features like URIs.using namespace web::http; // Common HTTP functionalityusing namespace web::http::client; // HTTP client featuresusing namespace concurrency::streams; // Asynchronous streamsvoid TestPostRequest(const std::wstring& wsServersite, const std::wstring& wsURI, const std::wstring &userName, const std::wstring &passWord){	utility::stringstream_t msgStream;	try	{		json::value reqMsg;		reqMsg[U("userName")] = json::value::string(userName);		reqMsg[U("userPassword")] = json::value::string(passWord);		reqMsg.serialize(msgStream);	}	catch (const std::exception &e)	{		std::cerr << e.what() << '\n';		return;	}	try	{		// default timeout is 30s, set to 10s		http_client_config config;		config.set_timeout(utility::seconds(10));		// Create http_client to send the request.		http_client client(wsServersite);		// Build request URI and start the request.		uri_builder builder(wsURI);		// request，同步方式		http_request Request(methods::POST);		//Request.headers().add(L"Authorization", L"Bearer cn-5f6c09ce-2d53-4146-b6d4-45c338da581d");		Request.set_request_uri(builder.to_string());		Request.set_body(msgStream.str(), U("application/json"));		// request，同步方式		http_response response = client.request(Request).get();		//http_response response = client.request(methods::POST, builder.to_string(), msgStream.str(), U("application/json")).get();		if (response.status_code() == status_codes::OK)		{			try			{				// 从返回的json中获取字段值				/*const json::value &jv = response.extract_json().get();				const web::json::object &jobj = jv.as_object();				auto result_code = jobj.at(U("code")).as_integer();				std::wstring result_msg = jobj.at(U("msg")).as_string().c_str();				std::wcout.imbue(std::locale("chs"));				std::wcout << "code: " << result_code << "; msg: " << result_msg << std::endl;*/				// 输出返回的所有json内容				std::wstring result_msg = response.extract_string().get();				std::wcout.imbue(std::locale("chs"));				std::wcout << "result_msg: " << result_msg << std::endl;			}			catch (const std::exception &e)			{				std::wcout << e.what() << std::endl;			}		}		else		{			std::wcout << "error:" << response.status_code() << std::endl;		}	}	catch (const std::exception &e)	{		std::cerr << e.what() << '\n';	}}int main(int argc, char* argv[]){// 测试POST接口std::wstring userName = L"admin";std::wstring password = L"123456";std::wstring wsServersite = L";;std::wstring wsURI = L"/auth/web/login";TestPostRequest(wsServersite, wsURI,userName, password);}

2）Get接口使用：

#include "stdafx.h"#include <cpprest/http_client.h>#include <cpprest/filestream.h>using namespace utility; // Common utilities like string conversionsusing namespace web; // Common features like URIs.using namespace web::http; // Common HTTP functionalityusing namespace web::http::client; // HTTP client featuresusing namespace concurrency::streams; // Asynchronous streamsvoid TestGetRequest(const std::wstring& wsServersite, const std::wstring& wsURI, const std::wstring& wsURIName, const std::wstring& wsURIValue){// Open stream to output file.try{// default timeout is 30s, set to 10shttp_client_config config;config.set_timeout(utility::seconds(10));// Create http_client to send the request.http_client client(wsServersite);// Build request URI and start the request.uri_builder builder(wsURI);builder.append_query(wsURIName, wsURIValue);// Add Headerhttp_request Request(methods::GET);Request.headers().add(L"x-userid", L"69003613");Request.headers().add(L"Authorization", L"Bearer cn-45c338da581d");Request.set_request_uri(builder.to_string());// request，同步方式http_response response = client.request(Request).get();if (response.status_code() == status_codes::OK){// 输出返回的所有json内容std::wstring result_msg = response.extract_string().get();std::wcout.imbue(std::locale("chs"));std::wcout << "result_msg: " << result_msg << std::endl;}else{std::wcout << "error:" << response.status_code() << std::endl;}}catch (const std::exception &e){printf("Error exception:%s\n", e.what());}}int main(int argc, char* argv[]){std::wstring wsServersite = L";;std::wstring wsURI = L"/messag/projects/count";std::wstring wsName = L"projectId";std::wstring wsValue = L"a6a6aa80-bfaf412";TestGetRequest(wsServersite, wsURI, wsName, wsValue);return 0;}

本人采用了vc141编译cppRestSdk包，可以支持VS2015 / VS2017 / VS2019的使用，包含：include、lib、dll文件夹，提供x64位debug和release编译结果。如有兴趣可以去下载，下载地址：；