1 Beast简介
Beast是Boost中关于http(s)/websocket（s)的库，首发于boost 1.66（2016年），是比较新的库，它主要包含了http、websocket协议的解析（反序列化）和封装（序列化）以及关于网络的操作，它以asio为基础，但似乎又想隔离Asio。本文从0到1详细描述其搭建步骤以及思路。
2 搭建流程
2.1 boost和jsoncpp下载和安装
提前下载好这两个，下载和准备工作，参下面这两篇文章，
Windows下Boost库的安装与使用
C++上Json的使用说明（从下载到生成库再到使用）
2.2 项目创建和配置
1、打开visual studio，创建一个控制台应用，空项目也可以，项目名称和位置随意。
2、配置项目，右键项目，打开属性，点击左侧的VC++目录，选择包含目录选项，如下编辑配置，
3、同上，再次编辑配置库目录，见下图
4、配置jsoncpp库文件，按照如下顺序进行配置，第四步替换为自己的jsoncpp路径即可。
至此，所有配置完成。
2.3 代码
#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/beast/version.hpp>
#include <boost/asio.hpp>
#include <chrono>
#include <cstdlib>
#include <ctime>
#include <iostream>
#include <memory>
#include <string>
#include<json/json.h>
#include<json/value.h>
#include<json/reader.h>
namespace beast = boost::beast; // from <boost/beast.hpp>
namespace http = beast::http; // from <boost/beast/http.hpp>
namespace net = boost::asio; // from <boost/asio.hpp>
using tcp = boost::asio::ip::tcp; // from <boost/asio/ip/tcp.hpp>
namespace my_program_state
{
std::size_t
request_count()
{
static std::size_t count = 0;
return ++count;
}
std::time_t
now()
{
return std::time(0);
}
}
class http_connection : public std::enable_shared_from_this<http_connection>
{
public:
http_connection(tcp::socket socket)
: socket_(std::move(socket))
{
}
// Initiate the asynchronous operations associated with the connection.
void
start()
{
read_request();
check_deadline();
}
private:
// The socket for the currently connected client.
tcp::socket socket_;
// The buffer for performing reads.
beast::flat_buffer buffer_{
8192};
// The request message.
http::request<http::dynamic_body> request_;
// The response message.
http::response<http::dynamic_body> response_;
// The timer for putting a deadline on connection processing.
net::steady_timer deadline_{
socket_.get_executor(), std::chrono::seconds(60)};
// Asynchronously receive a complete request message.
void
read_request()
{
auto self = shared_from_this();
http::async_read(
socket_,
buffer_,
request_,
[self](beast::error_code ec,
std::size_t bytes_transferred)
{
boost::ignore_unused(bytes_transferred);
if (!ec)
self->process_request();
});
}
// Determine what needs to be done with the request message.
void
process_request()
{
response_.version(request_.version());
response_.keep_alive(false);
switch (request_.method())
{
case http::verb::get:
response_.result(http::status::ok);
response_.set(http::field::server, "Beast");
create_response();
break;
case http::verb::post:
response_.result(http::status::ok);
response_.set(http::field::server, "Beast");
create_post_response();
break;
default:
// We return responses indicating an error if
// we do not recognize the request method.
response_.result(http::status::bad_request);
response_.set(http::field::content_type, "text/plain");
beast::ostream(response_.body())
<< "Invalid request-method '"
<< std::string(request_.method_string())
<< "'";
break;
}
write_response();
}
// Construct a response message based on the program state.
void
create_response()
{
if (request_.target() == "/count")
{
response_.set(http::field::content_type, "text/html");
beast::ostream(response_.body())
<< "<html>\n"
<< "<head><title>Request count</title></head>\n"
<< "<body>\n"
<< "<h1>Request count</h1>\n"
<< "<p>There have been "
<< my_program_state::request_count()
<< " requests so far.</p>\n"
<< "</body>\n"
<< "</html>\n";
}
else if (request_.target() == "/time")
{
response_.set(http::field::content_type, "text/html");
beast::ostream(response_.body())
<< "<html>\n"
<< "<head><title>Current time</title></head>\n"
<< "<body>\n"
<< "<h1>Current time</h1>\n"
<< "<p>The current time is "
<< my_program_state::now()
<< " seconds since the epoch.</p>\n"
<< "</body>\n"
<< "</html>\n";
}
else
{
response_.result(http::status::not_found);
response_.set(http::field::content_type, "text/plain");
beast::ostream(response_.body()) << "File not found\r\n";
}
}
// Asynchronously transmit the response message.
void
write_response()
{
auto self = shared_from_this();
response_.content_length(response_.body().size());
http::async_write(
socket_,
response_,
[self](beast::error_code ec, std::size_t)
{
self->socket_.shutdown(tcp::socket::shutdown_send, ec);
self->deadline_.cancel();
});
}
// Check whether we have spent enough time on this connection.
void
check_deadline()
{
auto self = shared_from_this();
deadline_.async_wait(
[self](beast::error_code ec)
{
if (!ec)
{
// Close socket to cancel any outstanding operation.
self->socket_.close(ec);
}
});
}
void create_post_response() {
if (request_.target() == "/email")
{
auto& body = this->request_.body();
auto body_str = boost::beast::buffers_to_string(body.data());
std::cout << "receive body is " << body_str << std::endl;
this->response_.set(http::field::content_type, "text/json");
Json::Value root;
Json::Reader reader;
Json::Value src_root;
bool parse_success = reader.parse(body_str, src_root);
if (!parse_success) {
std::cout << "Failed to parse JSON data!" << std::endl;
root["error"] = 1001;
std::string jsonstr = root.toStyledString();
beast::ostream(this->response_.body()) << jsonstr;
return;
}
auto email = src_root["email"].asString();
std::cout << "email is " << email << std::endl;
root["error"] = 0;
root["email"] = src_root["email"];
root["msg"] = "recevie email post success";
std::string jsonstr = root.toStyledString();
beast::ostream(this->response_.body()) << jsonstr;
}
else
{
response_.result(http::status::not_found);
response_.set(http::field::content_type, "text/plain");
beast::ostream(response_.body()) << "File not found\r\n";
}
}
};
void
http_server(tcp::acceptor& acceptor, tcp::socket& socket)
{
acceptor.async_accept(socket,
[&](beast::error_code ec)
{
if (!ec)
std::make_shared<http_connection>(std::move(socket))->start();
http_server(acceptor, socket);
});
}
int main(int argc, char* argv[])
{
try
{
// Check command line arguments.
/*if (argc != 3)
{
std::cerr << "Usage: " << argv[0] << " <address> <port>\n";
std::cerr << " For IPv4, try:\n";
std::cerr << " receiver 0.0.0.0 80\n";
std::cerr << " For IPv6, try:\n";
std::cerr << " receiver 0::0 80\n";
return EXIT_FAILURE;
}*/
auto const address = net::ip::make_address("127.0.0.1");
unsigned short port = static_cast<unsigned short>(8080);
net::io_context ioc{
1};
tcp::acceptor acceptor{
ioc, {
address, port }};
tcp::socket socket{
ioc};
http_server(acceptor, socket);
ioc.run();
}
catch (std::exception const& e)
{
std::cerr << "Error: " << e.what() << std::endl;
return EXIT_FAILURE;
}
}
2.4 测试
get请求，url为localhost:8080/time
post请求，url为localhost:8080/email
