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**Drogon** is a C++14/17-based HTTP application framework. Drogon can be used to easily build various types of web application server programs using C++. **Drogon** is the name of a dragon in the American TV series "Game of Thrones" that I really like.
Drogon's main application platform is Linux. It also supports Mac OS and FreeBSD. Currently, it does not support windows. Its main features are as follows:
* Use a non-blocking I/O network lib based on epoll (kqueue under MacOS/FreeBSD) to provide high-concurrency, high-performance network IO, please visit the [benchmarks](https://github.com/an-tao/drogon/wiki/benchmarks) page for more details;
* Support back-end rendering, the controller generates the data to the view to generate the Html page, the view is described by a "JSP-like" CSP file, the C++ code is embedded into the Html page by the CSP tag, and the drogon command-line tool automatically generates the C++ code file for compilation;
* Support view page dynamic loading (dynamic compilation and loading at runtime);
* Provide a convenient and flexible routing solution from the path to the controller handler;
* Support filter chains to facilitate the execution of unified logic (such as login verification, Http Method constraint verification, etc.) before controllers;
Unlike most C++ frameworks, the main program of the drogon application can be kept clean and simple. Drogon uses a few tricks to decouple controllers from the main program. The routing settings of controllers can be done through macros or configuration file.
Below is the main program of a typical drogon application:
```c++
#include <drogon/drogon.h>
using namespace drogon;
int main()
{
app().setLogPath("./");
app().setLogLevel(trantor::Logger::WARN);
app().addListener("0.0.0.0", 80);
app().setThreadNum(16);
app().enableRunAsDaemon();
app().run();
}
```
It can be further simplified by using configuration file as follows:
```c++
#include <drogon/drogon.h>
using namespace drogon;
int main()
{
app().loadConfigFile("./config.json");
app().run();
}
```
Drogon provides some interfaces for adding controller logic directly in the main() function, but unless your logic is very simple, we don't recommend using them. Instead, we create an HttpSimpleController as follows:
```c++
/// The TestCtrl.h file
#pragma once
#include <drogon/HttpSimpleController.h>
using namespace drogon;
class TestCtrl:public drogon::HttpSimpleController<TestCtrl>
**Don't be scared by the code. Most of the above programs can be automatically generated by the command line tool `drogon_ctl` provided by drogon**. All the user needs to do is add their own business logic. In the example, the controller returns a `Hello, world!` string when the client accesses the `http://ip/test` URL.
As you can see, users can use the `HttpController` to map paths and parameters at the same time. This is a very convenient way to create a RESTful API application.
After compiling all of the above source files, we get a very simple web application. This is a good start. **for more information, please visit the [wiki](https://github.com/an-tao/drogon/wiki) site**
