Boost::Beast minimal HTTP server example with request routing using Boost::URL and JSON responses
In our previous post Boost::Beast minimal HTTP server example using boost::json we showcased a minimal example for a Boost::Beast-based webserver in modern C++.
In this post, we’ll extend this example to include request routing using Boost::URL.
Request routing HOWTO
Routing the requests is simple:
url_view parsed_url(req.target());
auto params = parsed_url.params();
// NOTE: Path is /api/login for the example above
auto path = parsed_url.path();
if(path == "/hello") {
// TODO: Handle /hello
} else if(path == "/world") {
// TODO: Handle /world
} else {
res.result(http::status::not_found);
res.set(http::field::content_type, "text/plain");
res.body() = "Not Found";
res.prepare_payload();
}
Full example
#include <boost/beast/core.hpp>
#include <boost/beast/http.hpp>
#include <boost/asio.hpp>
#include <boost/json.hpp>
#include <boost/url.hpp>
#include <iostream>
using namespace boost::urls;
using std::cout, std::endl;
#include <iostream>
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>
namespace json = boost::json; // from <boost/json.hpp>
using tcp = boost::asio::ip::tcp; // from <boost/asio/ip/tcp.hpp>
// Function to handle an HTTP request and generate a JSON response
void handle_request(const http::request<http::string_body>& req, http::response<http::string_body>& res) {
// For this example, only GET request
if (req.method() == http::verb::get) {
// NOTE: For http://127.0.0.1:8080/api/login?username=myusername&password=mypassword
// req.target() will be /api/login?username=myusername&password=mypassword
url_view parsed_url(req.target());
auto params = parsed_url.params();
// NOTE: Path is /api/login for the example above
auto path = parsed_url.path();
if(path == "/hello") {
json::object json_response;
json_response["message"] = "Hello, World!";
json_response["status"] = "success";
res.result(http::status::ok);
res.set(http::field::content_type, "application/json");
res.body() = json::serialize(json_response);
res.prepare_payload();
} else if(path == "/world") {
json::object json_response;
json_response["message"] = "World, Hello!";
json_response["status"] = "success";
res.result(http::status::ok);
res.set(http::field::content_type, "application/json");
res.body() = json::serialize(json_response);
res.prepare_payload();
} else {
res.result(http::status::not_found);
res.set(http::field::content_type, "text/plain");
res.body() = "Not Found";
res.prepare_payload();
}
} else {
res.result(http::status::method_not_allowed);
res.set(http::field::content_type, "text/plain");
res.body() = "Method Not Allowed";
res.prepare_payload();
}
}
// Session to handle communication with a single client
void session(tcp::socket socket) {
try {
beast::flat_buffer buffer;
// Read an HTTP request
http::request<http::string_body> req;
http::read(socket, buffer, req);
// Prepare the response
http::response<http::string_body> res;
handle_request(req, res);
// Write the response
http::write(socket, res);
} catch (const std::exception& e) {
std::cerr << "Error in session: " << e.what() << '\n';
}
}
// Main function to set up the server
int main() {
try {
const auto address = net::ip::make_address("127.0.0.1");
const unsigned short port = 8080;
net::io_context ioc;
// Create and bind the acceptor
tcp::acceptor acceptor{ioc, {address, port}};
std::cout << "HTTP server is running on http://127.0.0.1:8080\n";
while (true) {
// Accept a new connection
tcp::socket socket{ioc};
acceptor.accept(socket);
// Handle the session in a new thread
std::thread{&session, std::move(socket)}.detach();
}
} catch (const std::exception& e) {
std::cerr << "Error: " << e.what() << '\n';
return 1;
}
}
How to compile
g++ -std=c++17 -O2 httpserver.cpp -o httpserver -lboost_system -lboost_url -lboost_thread -lboost_json -lpthread
How to test
In your terminal, run:
./httpserver
Open your browser and navigate to http://127.0.0.1:8080/hello
and http://127.0.0.1:8080/world
to the JSON responses.
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