{"id":1313,"date":"2024-03-06T10:45:05","date_gmt":"2024-03-06T08:45:05","guid":{"rendered":"http:\/\/www.lafabriquedecode.com\/blog\/?p=1313"},"modified":"2026-03-04T22:14:57","modified_gmt":"2026-03-04T20:14:57","slug":"mongodb-et-cplusplus","status":"publish","type":"post","link":"http:\/\/www.lafabriquedecode.com\/blog\/2024\/03\/mongodb-et-cplusplus\/","title":{"rendered":"Interroger un cluster MongoDB Atlas avec C++"},"content":{"rendered":"\n
\"\"<\/a><\/figure>\n\n\n\n

J\u2019ai d\u00e9cid\u00e9 de me replonger dans C++<\/strong> le temps d\u2019un exercice propos\u00e9 aux \u00e9tudiants qui suivent ma formation sur MongoDB<\/strong> en \u00e9cole d\u2019ing\u00e9nieur. N\u2019ayant pas pratiqu\u00e9 ce langage depuis l\u2019\u00e9poque o\u00f9 la monnaie nationale \u00e9tait encore le franc, j\u2019ai renou\u00e9 avec plaisir avec le langage de Bjarne Stroustrup<\/strong>. Voici les diff\u00e9rentes \u00e9tapes qui m\u2019ont conduit \u00e0 \u00e9crire le code permettant d\u2019interroger, en C++, un cluster MongoDB<\/strong> h\u00e9berg\u00e9 sur Atlas<\/strong>.<\/p>\n\n\n\n

Tout d’abord, il m’a fallu installer le pilote (driver<\/em>) d\u00e9di\u00e9 \u00e0 ce langage : mongocxx<\/a>.
<\/p>\n\n\n\n

Installation et compilation du pilote mongocxx<\/h2>\n\n\n\n

Rien de plus simple pour y parvenir :<\/p>\n\n\n\n

\n
\n    cd mongo-cxx-driver\n    mkdir build && cd build\n    cmake -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=\/usr\/local ..\n    make -j$(nproc)\n    sudo make install\n<\/pre><\/div><\/div><\/div>\n<\/div><\/div>\n\n\n\n
Le programme principal<\/h2>\n\n\n\n
Une fois le driver install\u00e9, j’ai pu commencer \u00e0 coder le petit programme pour acc\u00e9der  \u00e0 mon cluster<\/em> Atlas et y ex\u00e9cuter toutes les requ\u00eates pr\u00e9par\u00e9es dans mon header exercices.hpp<\/strong> . Le voici :<\/p>\n\n\n
\n#include <iostream>\n#include <bsoncxx\/json.hpp>\n#include <mongocxx\/client.hpp>\n#include <mongocxx\/instance.hpp>\n#include <mongocxx\/uri.hpp>\n#include <mongocxx\/exception\/exception.hpp>\n#include "exercices.hpp" \n\nusing bsoncxx::to_json;\n\nint main() {\n\n    const std::string USERNAME      = "mongosensei";\n    const std::string PASSWORD      = "xxxxx";\n    const std::string DATABASE      = "xxxxx";\n    const std::string COLLECTION    = "salles";\n    const std::string ATLAS_CLUSTER = "xxx.mongodb.net";\n\n    mongocxx::instance inst{};\n\n    try {\n        std::string uriString = "mongodb+srv:\/\/" + USERNAME + ":" + PASSWORD + "@" + ATLAS_CLUSTER + "\/" + DATABASE;\n        mongocxx::uri uri(uriString);\n        mongocxx::client conn(uri);\n\n        std::vector<bsoncxx::document::value> exercices = getExercices();\n\n        for (const auto& exercice : exercices) {\n            auto numExercice = exercice["num"].get_int32();\n            auto filterDocument = exercice["filtre"].get_document();\n            auto projectionDocument = exercice["options"]["projection"].get_document();\n            \n            auto options = mongocxx::options::find{};\n            options.projection(projectionDocument.view());\n\n            auto collection = conn[DATABASE][COLLECTION];\n            auto cursor = collection.find(filterDocument.view(), options);\n\n            int nbDocuments = 0;\n\n            for (auto&& doc : cursor) {\n                nbDocuments++;\n                std::cout << bsoncxx::to_json(doc) << std::endl;\n            }\n\n            std::cout << "Nb de documents pour l'exercice " << numExercice << " : " << nbDocuments << std::endl;\n        }\n\n    } catch (const mongocxx::exception& e) {\n        std::cerr << "Erreur de connexion : " << e.what() << std::endl;\n        return EXIT_FAILURE;\n    }\n\n    return EXIT_SUCCESS;\n}\n<\/pre><\/div>\n\n\n
Ce programme fait appel \u00e0 un fichier qui contient la solution \u00e0 chacun des exercices contenus dans le PDF dont le lien a \u00e9t\u00e9 donn\u00e9 plus haut. Voici ce \u00e0 quoi il ressemble :<\/p>\n\n\n
\n#ifndef EXERCICES_HPP\n#define EXERCICES_HPP\n\n#include <vector>\n#include <bsoncxx\/builder\/basic\/document.hpp>\n\ntime_t parseDate(const std::string& dateStr) {\n    std::tm tm = {};\n    strptime(dateStr.c_str(), "%Y-%m-%d", &tm);\n    return mktime(&tm);\n}\n\nstd::vector<bsoncxx::document::value> getExercices() {\n    using bsoncxx::builder::basic::kvp;\n    using bsoncxx::builder::basic::make_document;\n    using bsoncxx::builder::basic::make_array;\n\n    std::string date_str = "2021-11-15";\n    auto timestamp = std::chrono::milliseconds{parseDate(date_str) * 1000};\n\n    std::vector<bsoncxx::document::value> exercices = {\n        make_document(\n            kvp("num", 1),\n            kvp("filtre", make_document(\n                kvp("smac", true)\n            )),\n            kvp("options", make_document(\n                kvp("projection", make_document(\n                    kvp("_id", true),\n                    kvp("nom", true)\n                ))\n            ))\n        ),\n        make_document(\n            kvp("num", 2),\n            kvp("filtre", make_document(\n                kvp("capacite", make_document(\n                    kvp("$gt", bsoncxx::types::b_int64{1000})\n                ))\n            )),\n            kvp("options", make_document(\n                kvp("projection", make_document(\n                    kvp("_id", false),\n                    kvp("nom", true)\n                ))\n            ))\n        ),\n        make_document(\n            kvp("num", 3),\n            kvp("filtre", make_document(\n                kvp("adresse.numero", make_document(\n                    kvp("$exists", false)\n                ))\n            )),\n            kvp("options", make_document(\n                kvp("projection", make_document(\n                    kvp("_id", true)\n                ))\n            ))\n        ),\n        make_document(\n            kvp("num", 4),\n            kvp("filtre", make_document(\n                kvp("avis", make_document(\n                    kvp("$size", bsoncxx::types::b_int64{1})\n                ))\n            )),\n            kvp("options", make_document(\n                kvp("projection", make_document(\n                    kvp("nom", true)\n                ))\n            ))\n        ),\n        make_document(\n            kvp("num", 5),\n            kvp("filtre", make_document(\n                kvp("styles", "blues")\n            )),\n            kvp("options", make_document(\n                kvp("projection", make_document(\n                    kvp("_id", false),\n                    kvp("styles", true)\n                ))\n            ))\n        ),\n        make_document(\n            kvp("num", 6),\n            kvp("filtre", make_document(\n                kvp("styles.0", "blues")\n            )),\n            kvp("options", make_document(\n                kvp("projection", make_document(\n                    kvp("_id", false),\n                    kvp("styles", true)\n                ))\n            ))\n        ),\n        make_document(\n            kvp("num", 7),\n            kvp("filtre", make_document(\n                kvp("$and", make_array(\n                    make_document(\n                        kvp("adresse.codePostal", bsoncxx::types::b_regex{"^84"}),\n                        kvp("capacite", make_document(\n                            kvp("$lt", 500)\n                        ))\n                    )\n                ))\n            )),\n            kvp("options", make_document(\n                kvp("projection", make_document(\n                    kvp("_id", false),\n                    kvp("adresse.ville", true)\n                ))\n            ))\n        ),\n        make_document(\n            kvp("num", 8),\n            kvp("filtre", make_document(\n                kvp("$or", make_array(\n                    make_document(\n                        kvp("_id", make_document(kvp("$mod", make_array(2, 0))))\n                    ),\n                    make_document(\n                        kvp("avis", make_document(\n                            kvp("$exists", false)\n                        ))\n                    )\n                ))\n            )),\n            kvp("options", make_document(\n                kvp("projection", make_document(\n                    kvp("_id", true)\n                ))\n            ))\n        ),\n        make_document(\n            kvp("num", 9),\n            kvp("filtre", make_document(\n                kvp("avis", make_document(\n                    kvp("$elemMatch", make_document(\n                        kvp("note", make_document(\n                            kvp("$gte", 8),\n                            kvp("$lte", 10)\n                        ))\n                    ))\n                ))\n            )),\n            kvp("options", make_document(\n                kvp("projection", make_document(\n                    kvp("_id", false),\n                    kvp("nom", true)\n                ))\n            ))\n        ),\n        make_document(\n            kvp("num", 10),\n            kvp("filtre", make_document(\n                kvp("avis.date", make_document(\n                        kvp("$gt", bsoncxx::types::b_date{timestamp}\n                    ))\n                ))\n            ),\n            kvp("options", make_document(\n                kvp("projection", make_document(\n                    kvp("_id", false),\n                    kvp("nom", true)\n                ))\n            ))\n        ),\n    };\n\n    return exercices;\n}\n\n#endif \/\/ EXERCICES_HPP\n<\/pre><\/div>\n\n\n
La fonction parseDate<\/em> est l\u00e0 pour nous faciliter la transformation des dates pour leur utilisation avec mes m\u00e9thodes de la lib BSON, elle ne sert ici qu’une fois.<\/p>\n\n\n\n
Pour construire les documents, j’ai utilis\u00e9 la version basic<\/strong> du builder BSON, la version stream<\/strong> \u00e9tant beaucoup moins lisible pour moi.<\/p>\n\n\n\n
Compilation et ex\u00e9cution du code<\/h2>\n\n\n\n
J’ai essay\u00e9 plusieurs solutions :<\/p>\n\n\n\n