RESTful API Server | Qt HTTP Server | Qt 6.12.0
Description: Example of how to create a RESTful API server using the QHttpServer.
Keywords: example

- Qt 6.12
- Qt HTTP Server
- Qt HTTP Server Examples
- RESTful API Server
- Qt 6.12.0 Reference Documentation

# RESTful API Server

Example of how to create a RESTful API server using the QHttpServer.

This example shows how to create and host simple RESTful web APIs in a small application using the QHttpServer class. This server accepts calls in REST style and can be used with its counterpart example RESTful Color Palette API client on the client side.

An application that obeys the REST constraints may be informally described as RESTful. The RESTful API Server allows create, read, update and delete operations of colors (unknown resource to be compatible with Reqres API) and users. The RESTful API Server also provides login/logout functionality. The example is based on Reqres API.

To run the server application, execute server binary:

     ./colorpaletteserver

or

     ./colorpaletteserver --port 1234

An optional `port` parameter may be provided to specify the port on which the server shall run.

     httpServer.route(
             QString("%1").arg(apiPath), QHttpServerRequest::Method::Get,
             [&api](const QHttpServerRequest &request) { return api.getPaginatedList(request); });

In the example above, the route is specified for the GET method, which returns the JSON array with paginated list of items stored. To achieve that, the QHttpServer::route() method is used with the QHttpServerRequest::Method::Get enumeration.

     httpServer.route(QString("%1/<arg>").arg(apiPath), QHttpServerRequest::Method::Get,
                      [&api](qint64 itemId) { return api.getItem(itemId); });

To get a single item from the list of entities, the item ID is passed in the request query.

     httpServer.route(QString("%1").arg(apiPath), QHttpServerRequest::Method::Post,
                      [&api, &sessionApi](const QHttpServerRequest &request) {
                          if (!sessionApi.authorize(request)) {
                              return QHttpServerResponse(
                                      QHttpServerResponder::StatusCode::Unauthorized);
                          }
                          return api.postItem(request);
                      });

In this example, the route accepts POST method, which adds a new entry to the item list and returns a JSON object that represents the added entry. This request must be authorized. To authorize the request the value of the header `TOKEN` must be equal to previously returned token from the `api/login` or the `api/register` methods.

     QHttpServerResponse postItem(const QHttpServerRequest &request)
     {
         const std::optional<QJsonObject> json = byteArrayToJsonObject(request.body());
         if (!json)
             return QHttpServerResponse(QHttpServerResponder::StatusCode::BadRequest);

         const std::optional<T> item = factory->fromJson(*json);
         if (!item)
             return QHttpServerResponse(QHttpServerResponder::StatusCode::BadRequest);
         if (data.contains(item->id))
             return QHttpServerResponse(QHttpServerResponder::StatusCode::AlreadyReported);

         const auto entry = data.insert(item->id, *item);
         return QHttpServerResponse(entry->toJson(), QHttpServerResponder::StatusCode::Created);
     }

Besides new entry as JSON object POST methods returns also different HTTP status code: `Created` for new entries, or `AlreadyReported` for pre-existing entries. This example makes use of an overload of QHttpServerResponse::QHttpServerResponse to send a JSON object and corresponding HTTP status code.

To create an entry, the request body must be a JSON object with `email` `first_name` `last_name` and `avatar` fields - to create new users. For example:

     {
         "email": "jane.doe@qt.io",
         "first_name": "Jane",
         "last_name": "Doe",
         "avatar": "/img/faces/1-image.jpg"
     }

Files:

- colorpalette/CMakeLists.txt
- colorpalette/apibehavior.h
- colorpalette/colorpalette.pro
- colorpalette/main.cpp
- colorpalette/types.h
- colorpalette/utils.h

Images:

- colorpalette/assets/img/1-image.jpg
- colorpalette/assets/img/10-image.jpg
- colorpalette/assets/img/11-image.jpg
- colorpalette/assets/img/12-image.jpg
- colorpalette/assets/img/2-image.jpg
- colorpalette/assets/img/3-image.jpg
- colorpalette/assets/img/4-image.jpg
- colorpalette/assets/img/5-image.jpg
- colorpalette/assets/img/6-image.jpg
- colorpalette/assets/img/7-image.jpg
- colorpalette/assets/img/8-image.jpg
- colorpalette/assets/img/9-image.jpg