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The Simplest Way to Set Up the Drogon C++ Framework

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The Simplest Way to Set Up the Drogon C++ Framework

Introduction

Drogon is a powerful and efficient C++ framework designed for building high-performance web applications. Its asynchronous, non-blocking nature makes it particularly well-suited for modern web development demands, allowing it to handle a large number of concurrent connections with minimal resource consumption. This article will guide you through the simplest way to set up the Drogon framework, enabling you to start building your own web applications quickly and easily.

Prerequisites

Before we begin, make sure you have the following prerequisites installed on your system:

C++ Compiler: You need a C++ compiler like GCC, Clang, or Microsoft Visual Studio.
CMake: A build system to compile Drogon projects. Download it from
https://cmake.org/download/ .
Git: For downloading the Drogon source code from GitHub. Install Git from
https://git-scm.com/downloads .

Setting up Drogon

Here's a step-by-step guide to setting up Drogon:

Install Drogon

The easiest way to install Drogon is using CMake. Follow these steps:

Create a new directory for your project:

mkdir my_drogon_project
cd my_drogon_project

Clone the Drogon repository:

git clone https://github.com/drogonframework/drogon.git

Create a CMakeLists.txt file: This file tells CMake how to build your project. Here's a basic example:
```
cmake_minimum_required(VERSION 3.10)
project(my_drogon_project)
```

add_subdirectory(drogon)
add_executable(my_app main.cpp)

target_link_libraries(my_app Drogon)

Generate build files: Run CMake to generate build files for your system:



  cmake .

Build the project: Now, build the project using the appropriate commands for your system. For example, on Linux, you'd use:



  make

Create a Basic Drogon Application

Now, let's create a simple Drogon application that serves a "Hello, World!" message:

// main.cpp
#include 


using namespace drogon;

class HelloWorldController : public HttpController

{

public:

    void  asyncHandleRequest(const HttpRequestPtr &req,

                              const std::function

                                  &callback) override

    {

        auto res = HttpResponse::newHttpMessage();

        res->setStatusCode(kHttpStatusOK);

        res->setBody("Hello, World!");

        callback(res);

    }

};

int main()

{

  drogon::app().loadConfig("config.json");

  drogon::app().registerHttpController();

  drogon::app().run();

  return 0;

}

In this code, we define a HelloWorldController class that inherits from HttpController. This class implements the asyncHandleRequest method, which is responsible for handling incoming HTTP requests. Inside this method, we create a new HttpResponse object, set its body to "Hello, World!", and call the callback function to return the response to the client.

In the main function, we load the configuration from a JSON file ("config.json"), register our HelloWorldController with the Drogon application, and finally start the application using drogon::app().run().

Run the Application

To run your Drogon application, simply execute the built executable:

./my_app

You should see a message indicating that Drogon is running on the default port (8080):

Open your web browser and navigate to http://localhost:8080. You should see the "Hello, World!" message rendered in your browser.

Key Features of Drogon

Here are some of the key features of Drogon that make it a powerful choice for web development:

Asynchronous, Non-Blocking Architecture: Drogon leverages asynchronous programming and non-blocking I/O to handle a large number of concurrent requests efficiently. This makes it ideal for applications with high concurrency needs.
HTTP/1.1 and HTTP/2 Support: Drogon offers comprehensive support for both HTTP/1.1 and HTTP/2 protocols, enabling you to build applications that can leverage the performance benefits of the latest HTTP standard.
Powerful Routing System: Drogon provides a flexible routing system that allows you to define how incoming HTTP requests are mapped to your application's handlers. You can easily create RESTful APIs with well-defined routes.
Built-in Templating Engine: Drogon includes a built-in templating engine that simplifies dynamic content generation. You can create HTML templates and seamlessly integrate them with your application logic.
Middleware Support: Middleware allows you to execute code before or after handling a request. This can be used for tasks like authentication, authorization, logging, or request/response transformations.
Database Integration: Drogon integrates seamlessly with popular C++ database libraries like MySQL, PostgreSQL, MongoDB, and Redis. It provides convenient APIs for interacting with databases.
WebSocket Support: Drogon enables you to build real-time applications using WebSockets, allowing for bidirectional communication between your server and clients.
Excellent Documentation: Drogon has extensive documentation, including tutorials, guides, and API references.

Going Beyond the Basics

This basic example serves as a foundation. You can extend this further by incorporating more features of Drogon:

Handling Different HTTP Methods

Drogon supports various HTTP methods (GET, POST, PUT, DELETE, etc.). You can handle different methods within your controller:

class MyController : public HttpController
{
public:
// GET method handling
void doGet(const HttpRequestPtr& req,
          const std::function &callback) override
{
auto res = HttpResponse::newHttpMessage();
res->setStatusCode(kHttpStatusOK);
res->setBody("GET request received!");
callback(res);
}

// POST method handling
void doPost(const HttpRequestPtr& req,
const std::function &callback) override
{
auto res = HttpResponse::newHttpMessage();
res->setStatusCode(kHttpStatusOK);
res->setBody("POST request received!");
callback(res);
}
// ...other methods (PUT, DELETE)
};

Using Templating

Drogon provides a simple templating engine to generate dynamic HTML. Create a template file (e.g., "index.html"):

<!DOCTYPE html>

My Drogon App

Welcome to my Drogon application!

This is dynamic content generated using Drogon's templating.

And use it in your controller:



class MyController : public HttpController

{

public:

  void doGet(const HttpRequestPtr& req,

              const std::function &callback) override

  {

    auto res = HttpResponse::newHttpMessage();

    res->setStatusCode(kHttpStatusOK);

    // Render the template

    res->setTemplate("index.html"); 

    callback(res);

  }

};

Working with Databases

You can connect to databases like MySQL, PostgreSQL, MongoDB, etc. using Drogon's database integration:

#include  // Include for database operations


class MyController : public HttpController

{

public:

  void doGet(const HttpRequestPtr& req,

              const std::function &callback) override

  {

    auto res = HttpResponse::newHttpMessage();

    res->setStatusCode(kHttpStatusOK);
// Connect to the database (using your own configuration)
auto dbClient = DbClient::newDbClient("mysql", "localhost", "user", "password", "database");

// Execute a query (replace with your own query)
dbClient-&gt;execSqlAsync(
    "SELECT * FROM users",
    [res, callback](const Result &amp;result) {
      // Handle the result (process data, construct the response)
      if (result.success()) {
        res-&gt;setBody("Data fetched successfully!");
      } else {
        res-&gt;setBody("Error fetching data");
        res-&gt;setStatusCode(kHttpStatusInternalServerError);
      }
      callback(res);
    });

}

};

Using Middleware

Middleware can be used for various tasks like authentication, logging, and more:

class MyMiddleware : public HttpMiddleware
{
public:
void handleRequest(
  const HttpRequestPtr &req,
  const std::function &next) override
{
// Perform some action before proceeding to the next handler
LOG_INFO << "Middleware: Request received!"; 

// Call the next handler in the chain
next(req);
}
};

int main()
{
drogon::app().loadConfig("config.json");
drogon::app().registerHttpController();
// Register the middleware
drogon::app().registerHttpMiddleware(); 
drogon::app().run();
return 0;
}

Conclusion

Drogon provides a robust and efficient C++ framework for building modern web applications. Its asynchronous, non-blocking nature allows you to handle a large number of concurrent requests efficiently, making it suitable for high-load applications. By following the steps outlined in this guide, you can quickly get started with Drogon and start building your own web applications.

Remember to explore the extensive documentation and tutorials provided by the Drogon community for more advanced features and use cases.