beast网络库搭建http服务器

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简介

前面的几篇文章已经介绍了如何使用asio搭建高并发的tcp服务器，以及http服务器。但是纯手写http服务器太麻烦了，有网络库beast已经帮我们实现了。这一期讲讲如何使用beast实现一个http服务器。

连接类

我们先实现http_server函数

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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);
		});
}

http_server中添加了异步接收连接的逻辑，当有新的连接到来时创建http_connection,然后启动服务，新连接监听对端数据。接下来http_server继续监听对端的新连接。
连接类http_connection里实现了start函数监听对端数据

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void start()
{
	read_request();
	check_deadline();
}

处理读请求,将读到的数据存储再成员变量request_中，然后调用process_request处理请求

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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();
		});
}

check_deadline主要时用来检测超时，当超过一定时间后自动关闭连接，因为http请求时短链接

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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);
			}
		});
}

process_request函数中区分请求的类型，进行不同类型的处理如post还是get请求

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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();
}

create_response函数中解析了不同的路由处理get请求

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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";
	}
}

create_post_response处理了post请求中的一部分路由

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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";
	}
}

write_response发送请求

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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();
	});
}

总结

本文介绍了如何使用beast网络库实现http服务器

视频连接https://space.bilibili.com/271469206/channel/collectiondetail?sid=313101

源码链接https://gitee.com/secondtonone1/boostasio-learn